Flood Damage Emergency Reconstruction Project ...gdb.mef.gov.kh/fderp-af/contents/uploads/2014/08/...Egis Eau Document quality information Flood Damage Emergency Reconstruction Project

KINGDOM OF CAMBODIA

Nation Religion King

Ministry of Water Resources and Meteorology

Asian Development Bank

Flood Damage Emergency Reconstruction Project – Additional Financing ADB Loan Number : 3125-CAM(SF)

GoA (DFAT) Grant Number: 0285-CAM(EF)

SUBPROJECT PROFILE

TRAPAING THMOR Version 1

December 2014

In association with

KEY CONSULTANTS (CAMBODIA)

Egis Eau Document quality information

Page 2 Flood Damage Emergency Reconstruction Project – Additional Financing Version 1

Document quality information

General information

Directed by Chann Sinath, Project Director, PIU

Author(s) FDERP-AF MOWRAM TA: Egis Eau/KCC

Project name Flood Damage Emergency Reconstruction Project – Additional Financing

Document name Trapaing Thmor Irrigation System

Date 9 December 2014

Reference

Addressee(s)

Sent to:

Name Organisation Sent on (date):

Huy Vantha Project Manager, PIU 9 December 14

Huy Vantha Project Manager, PIU 17 December 14

Copy to:

Name Organisation Sent on (date):

PIU (3) PIU 17 December 14

PCMU (2) PCMU

ADB (3) ADB

History of modifications

Version Date Written by Approved & signed by:

Version 1 9 December 14 FDERP-AF: Egis Eau/KCC Leighton Williams, TL/IE

Version 1 17 December 14 FDERP-AF: Egis Eau/KCC Leighton Williams, TL/IE

Egis Eau Contents


Contents

Chapter 1 - INTRODUCTION.............................................................................7

1. Background..................................................................................................7 1.1. FDERP-AF ...........................................................................................................7 1.2. History ..................................................................................................................8 1.3. Trapeang Thma Irrigation Rehabilitation Project .................................................8 1.4. Stung Sreng Water Resource Development Project .........................................12 1.5. Misuse and damage to irrigation structures.......................................................13 1.6. IUCN Protected Site...........................................................................................14

2. Flood Damage ............................................................................................14

Chapter 2 - SUB-PROJECT DESCRIPTION ...................................................15

1. Location......................................................................................................15 2. Existing Situation ......................................................................................15

2.1. Description of Facilities ......................................................................................15 2.2. State of Repair ...................................................................................................17 2.3. Irrigation Structure 1 Tilting Gates .....................................................................17

3. Socio-economic and Agriculture .............................................................18 3.1. Area....................................................................................................................18 3.2. Cultivated Area and Beneficiaries......................................................................18 3.3. Agriculture Practices ..........................................................................................19 3.4. Cropping Patterns ..............................................................................................20 3.5. Agricultural Product Marketing...........................................................................20 3.6. Economic Internal Rate of Return......................................................................22

4. FWUC/FWUG ..............................................................................................22 4.1. FWUC History and Establishment .....................................................................22 4.2. FWUC Membership List .....................................................................................23 4.3. FWUC Management of Trapaing Thmor Reservoir ...........................................26 4.4. Tourism Site .......................................................................................................27 4.5. Conclusion .........................................................................................................27

5. O&M ............................................................................................................28 5.1. Hydrology ...........................................................................................................28

Chapter 3 - SCOPE OF WORKS.....................................................................30

1. Proposed Interventions.............................................................................30 1.1. Stage 2 Civil Works............................................................................................30 1.2. Stage 3...............................................................................................................30

1.2.1. NCB Contract ...................................................................................................... 30 1.2.2. ICB Contract........................................................................................................ 30 1.2.3. Additional Works Recommended ........................................................................ 31

1.3. Automatic Tilting Gates......................................................................................31 2. Cost Estimate.............................................................................................31 3. Photographs...............................................................................................32

Chapter 4 - SUB-PROJECT SCREENING ......................................................35

1. General and Irrigation Specific Screening ..............................................35 1.1. Stage 2...............................................................................................................35 1.2. Stage 3...............................................................................................................35

2. Safeguards Screening: Resettlement ......................................................35 2.1. Scope of Land Acquisition and Resettlement ....................................................35 2.2. Resettlement Impact Categorisation Check-list.................................................35

Egis Eau Contents


2.3. Voluntary Resettlement......................................................................................36 2.4. Suggested Follow-up Activities ..........................................................................36

3. Safeguards Screening: Environment.......................................................36 3.1. Environmental Assessment Check-list...............................................................36 3.2. Beneficial impacts ..............................................................................................36 3.3. Potential Negative Environmental Impacts ........................................................37

3.3.1. Protected Sites .................................................................................................... 37 3.3.2. Siting concerns.................................................................................................... 37 3.3.3. Water User Conflicts ........................................................................................... 37 3.3.4. Salinity................................................................................................................. 37 3.3.5. Construction impacts........................................................................................... 37

3.4. Environmental Category ....................................................................................38 3.5. Environmental Management Plan......................................................................38

Chapter 5 - CONCLUSIONS............................................................................40

1. Screening ...................................................................................................40 2. Proposed Interventions.............................................................................41

References .....................................................................................................70

List of appendices

Appendix 1 – Hydrology...............................................................................................................42

Appendix 2 – Sketches of Emergency Repairs............................................................................55

Appendix 3 – Stage 2 Assessment and Confirmation Sheet .......................................................57

Appendix 4 – Selection Criteria Screening ..................................................................................58

Appendix 5 – Involuntary Resettlement Impact Check-list ..........................................................60

Appendix 6 – ADB Resettlement Principles and Policy Frameworks ..........................................61

Appendix 7 – Screening for Environmental Impacts....................................................................62

Appendix 8 – Environmental Management Plan (EMP) ..............................................................66

List of figures

Figure 1 Photographs of reservoir outlet structures..................................................................10

Figure 2 River and structures at Trapaing Thmor Reservoir ....................................................12

Figure 3 Constructed canals for Stung Sreng Water Resource Development Project, April 2014...............................................................................................................................13

Figure 4 Layout of main features of Trapaing Thmor Irrigation System ...................................16

Figure 5 – Existing Cropping Pattern Trapaing Subproject .........................................................20

Figure 6 Ang Trapaeng Thma FWUC Office.............................................................................23

Figure 7 Organization of Trapaing Thmor FWUC.....................................................................23

Figure 8 FWUC Membership application form..........................................................................26

Figure 9 Sample BANK and ISF receipts..................................................................................26

Figure 13 Trapaing Thmor reservoir catchment........................................................................42

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Figure 14 – Landsat image of flooded areas of Trapaing Thma and environs ............................44

Figure 15 – Radar image 30 August 2000...................................................................................44

Figure 16 – Summary of monthly rainfall at Thma Pouk..............................................................45

Figure 17 – Summary of monthly rainfall at Svay Chek...............................................................45

Figure 18 – Summary of monthly rainfall at Phnom Srok ............................................................46

Figure 19 Reservoir stage-storage relationship........................................................................48

Figure 20 Stage-discharge relationship for Trapaing Thmor outlet structures .........................49

Figure 21 Flood routing of 2013 flood before tilting gates opened ...........................................50

Figure 22 Flood routing of the design flood through Trapaing Thmor Reservoir......................51

List of tables

Table 1 Principal structures along Trapaing Thmor dam............................................................9

Table 2 Summary of existing irrigation infrastructure at Trapaing Thmor Irrigation System ...................................................................................................................................15

Table 3 – Area and population in the target area of Trapaing Thmor subproject ........................18

Table 4 Area and population in the target areas of Trapaing Thmor subproject ......................18

Table 5 – Agricultural practices at Trapaing Thmor subproject ...................................................20

Table 6 Without the project crop budget and gross margin ......................................................21

Table 7 – With the project crop budget and gross margin ...........................................................21

Table 8 – Economic Cash Flow at Trapaing Thmor subproject...................................................22

Table 9 – Trapaing Thmor FWUC Committee .............................................................................24

Table 10 Trapaing Thmor FWUGs Committees .......................................................................24

Table 11 – Daily raingauge records for locations closest to Trapaing Thmor Reservoir and command area .......................................................................................................................44

Table 12 Discharge to main canals during 2013 flood..............................................................52

Table 13 Discharge to main canals during the design flood .....................................................52

Table 14 – Water availability (MCM) entering Trapaing Thmor Reservoir ..................................53

Table 15 – Water availability (m3/s) entering Trapaing Thmor Reservoir ....................................54

Egis Eau Acronyms and Abbreviations


Acronyms and Abbreviations

ADB Asian Development Bank

ADRA Adventist Development and Relief Agency

CARM Cambodian Resident Mission (of ADB)

EA Executing Agency

EMP Environmental Management Plan

FDERP Flood Damage Emergency Reconstruction Project

FDERP-AF Flood Damage Emergency Reconstruction Project – Additional Financing

FSL Full Supply Level

FWUC Farmer Water User Community

FWUG Farmer Water User Group

GoA (DFAT) Government of Australia (Department of Foreign Affairs and Trade)

GTFM Generalised Tropical Flood Model

IA Implementing Agency

IEE Initial Environmental Examination

IMT Irrigation Management Transfer

IRS Irrigation Rehabilitation Study

MAF Mean Annual Flood

MEF Ministry of Economy and Finance

MOU Memorandum of Understanding

MOWRAM Ministry of Water Resources and Meteorology

O&M Operation and Maintenance

PAM Project Administration Manual

PCMU Project Coordination and Monitoring Unit (MEF)

PDWRAM Provincial Department of Water Resources and Meteorology

PIMD Participatory Irrigation Management Development

PIU Project Implementation Unit

PP Procurement Plan

RGC Royal Government of Cambodia

ROW Right-of-way

RRP Report and Recommendation of the President (to board of directors)

SAH Severely Affected Households

SPS Safeguard Policy Statement

TA Technical Assistance

TOR Terms of Reference

Egis Eau Subproject Profile – Trapaing Thmor Irrigation System


Chapter 1 - INTRODUCTION

1. Background

1.1. FDERP-AF

During the period September to November 2013, Cambodia and neighbouring countries suffered floods from the Mekong River and heavy rainfall in river catchments at similar levels to the floods which affected Cambodia in 2011. The 2013 flooding triggered RGC/ADB/GoA (DFAT)* emergency aid actions leading to Flood Damage Emergency Reconstruction Project – Additional Financing (FDERP-AF), as well as a review of damage to recently repaired infrastructure for the Flood Damage Emergency Reconstruction Project (FDERP) and the North West Irrigation Sector Project (NWISP).

An ADB fact finding mission on the 2013 flood damage undertaken in January 2014 produced a proposal for the Additional Financing to Flood Damage Emergency Reconstruction Project. The Bank and RGC initiated an emergency approach similar to the FDERP project to formulate a new project. The new project was renamed FDERP-AF and the agreement for Loan No.3125-CAM (SF) between RGC and ADB was finally signed 23 April 2014 and the loan became effective on the 30 May 2014. The loan is divided between several sectors with responsibility for Irrigation Rehabilitation and Flood Management as Output 3 implemented by the Ministry of Water Resources and Meteorology (MOWRAM).

The emergency repairs were categorised into 3 phases, Stage 1 to 3 as: Stage 1: Immediate repairs to re-establish use of the infrastructure on a temporary basis and restore communications. Stage 2: Fast track repairs where it was considered necessary to repair the damage before the next wet season to secure the existing (undamaged) works. Stage 3: Remaining flood damage restoration to complete the remaining damage repairs, preferably within the following two to three dry season construction periods.

The immediate Stage 1 repairs were done following the flood. At MOWRAM work on Stage 2 began in February 2014 and repair works commenced in June 2014 and will continue into 2015. Stage 3 works will be carried out during the dry season 2015 and 2016.

Stage 2 and Stage 3 works are identified in the Procurement Plan (PP). However the PP was a hastily prepared list of subprojects requiring interventions with guess estimates of cost. Thus it is a requirement of the Project Administration Manual (PAM) that Stage 3 subprojects be confirmed prior to commencing detailed design†.

* Royal Government of Cambodia/Asian Development Bank/Government of Australia (Department of Foriegn Affairs - Formerly AusAID)

† Actually, MOWRAM has substantially complete designs so the confirmation process is to review and improve these designs before proceeding to prepation of contract documents.



This subproject profile concerns the interventions for Trapaing Thmor Irrigation System located in Phnom Srok District, Banteay Meanchey Province. The work comprises: Clay cut-off trench to eliminate seepage through the earth embankment dam. Gabion mattress and box wave protection to upstream face of the dam. Improvements to Irrigation Structure 1 to improve erratic and unreliable operation of automatic

tilting gates. Construction of wave wall to crest of dam. Repairs to eroded and breached banks and embankments of irrigation canals and drains. Repairs to damaged irrigation and drainage structures. Additional and modified irrigation and drainage structures.

1.2. History

Trapaing Thmor Reservoir is also commonly known as Ang Trapaeng Thma. In this subproject profile the alternative spelling is used where it is directly quoting a reference document.

The water body has its origins in the Angkorian period, probably about 900 years ago when a causeway (road on embankment) was constructed along the same line as the modern dam across flood susceptible lowlands. It was part of the road network connecting the Angkor complex (Siem Reap) with Banteay Chhmar and beyond into modern day Thailand. There is visible evidence of the period throughout the district including scattered Prasat and baray. The District town of Phnom Srok has Angkorian origins with a traditional town and temple layout, set out on a compact grid arrangement clearly bounded by an enclosing square of baray with a dyke inside.

At its western extremity near Punley Cheung village the road also diverts the flow of the Prek Srae Memay and Prek Anlong Thom eastward into the present day reservoir via the Ou Chambak. There are at least two old stone Angkorian bridges. One Spean Preap was buried by the Khmer Rouge; the other just west of Phum Trapeang Thma remained visible until recent times but is not functioning. Inspection of old topographical maps and satellite images provide strong evidence that the Prek Srae Memay and Prek Anlong Thom originally flowed together into the Ou Preah Netr Preah to the south.

The 1:50,000 topographical maps dating from the late 1960s show the reservoir area as wetland with an outlet towards the south at Phum Trapeang Thma. No irrigation infrastructure is evident and it is probable that wet season rice was grown with flood spreading.

The Khmer Rouge regime saw the potential to use the road embankment as a dam to impound water on the north side for irrigation and flood control of the land to the south. Thus between 1975 and 1978 an 11 km long dike was built on top of the old road with a new 7 km dike enclosing the east side of the reservoir. Three large gated spillways and several smaller outlets were built together with a 1 km grid pattern of canals extending all the way south to National Road 6 and beyond. The works were never completed or properly commissioned. The dikes were half the design width and the gates were not finished or operational nor were bridges provided across two of the large structures. Consequently the reservoir could never be properly used for irrigation and the canals mostly functioned as drains, arguable with more negative than positive impact since they destroyed the natural drainage pattern.

1.3. Trapeang Thma Irrigation Rehabilitation Project

Between 2002 and 2004 MOWRAM with support from JICA undertook the Trapeang Thma Irrigation Rehabilitation Project. The rehabilitation objectives included: to (rehabilitate) spillways and main outlet structures;



to rehabilitate the existing dam; to install water control facilities including irrigation canals for appropriate water management

(estimated to be 11,000 ha); to extend the irrigation area based on capacity of rehabilitated facilities; to improve flood drainage channels connected to the reservoir; and to prepare for establishment of water user groups in the improved irrigation scheme through

labour contribution of affected farmers in the project implementation.

The key change with potential impact was that the spill level was raised from 15.99 m to 16.79 m elevation. The design drawings show high water level when the spillway is operating at 17.29 m elevation‡.

The project rehabilitated the three main irrigation structures which are combined spillways and head regulators and provided five gated culvert head regulators, all designed for release of irrigation water to canals downstream. In order to understand the complexity it is helpful to refer to the description of structures in Table 1, the photographs at Figure 1, and the map at Figure 2. The main spillway is Irrigation Structure 1 at the eastern end which is equipped with a pair of automatic counterweighted tilting gates. Irrigation Structures 2 and 3 both originally had fixed crest concrete weirs at a design level 16.79 m elevation (although actual levels were marginally different). However part of the weir at Irrigation Structure 2 has since been replaced by sluice gates, and the entire weir replaced by sluice gates at Irrigation Structure 3. Hence when the reservoir is full the backwater effect extends up the Ou Chambak and submerges all land below the 18.79 m contour.

Table 1 Principal structures along Trapaing Thmor dam

Structure Constructed Station Description Water source

Culvert 1 JICA 2004 15+340 Box culvert head regulator Reservoir

Irrigation Structure 1

JICA 2004 12+700 30 m bridge with 2 No 13.5 m wide automatic counterweighted tilting gates plus one 1.8 m sluice gate

Reservoir to MC1




JICA 2004, modified? But post 2008

9+550 30 m bridge originally with 2 No 13.5 m wide fixed crest weir plus one 1.8 m sluice gate. Currently 2 No 10 m wide fixed crest weir plus 5 No 1.8 m sluice gates

Reservoir to MC2


Culvert 5 JICA 2004 8+065 Box culvert head regulator High water from reservoir, low water from Ou Chambak

Culvert 6 2012 6+315 Box culvert head regulator Ou Chambak


JICA 2004, modified? But post 2008

6+075 10 m bridge originally with 8.0 m wide fixed crest weir plus one 1.8 m sluice gate. Currently 5 No 1.8 m sluice gates, no weir.

Ou Chambak to MC3

Culvert 7 JICA 2004 4+225 Box culvert head regulator Ou Chambak

‡ These elevations have been corrected to the datum used for the FDERP-AF designs, the elevations stated by JICA are 1.71 m higher.



Figure 1 Photographs of reservoir outlet structures

Irrigation Structure 1 from upstream, Oct 2014 Irrigation Structure 1 from downstream, Oct 2014

Culvert 2 from upstream, in early 2008 Culvert 3 from downstream, in early 2008

Irrigation Structure 2 in early 2008 before modification with additional sluice gates

Irrigation Structure 2 modified with additional gates,

September 2014. Looking downstream from Irrigation Structure 2,

September 2014



Culvert 4 from downstream early 2008 Vandalised Culvert 5 from upstream, early 2008

Irrigation Structure 3 and Ou Chambak in early 2008 before modification with additional sluice gates

Irrigation Structure 3 in early 2008 original weir before

modification with additional sluice gates Irrigation Structure 3 in March 2014 modified to five sluice

gates

Culvert 7 from upstream, early 2008 Culvert 7 from downstream, early 2008



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1.4. Stung Sreng Water Resource Development Project

In May 2011 Cambodia signed to receive a soft loan of US$52 million from the Export-Import Bank of China for the Stung Sreng Water Resource Development Project. This is a water resource development project affecting three provinces: Oddar Meanchey, Siem Reap and Banteay

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Meanchey and impacts on the Trapaing Thmor irrigation system. The project includes two master-canals total length more than 81 km and 18 sub-canals with a total length of 93.4 km, 130 bridges across canals and water gates. The headworks comprise an 800 m diversion weir and left and right bank gates to regulate downstream flow in the river and master canals. It is planned that the Project will irrigate 25,000 ha of rice fields in the wet season and 3,750 ha in the dry season, as well as supplying clean water and reducing flooding in the provinces.

There is very little public information on the project but the construction of the headworks and canal system were at an advanced stage during 2014. Completed and canals under construction are visible on current Google Earth imagery dated April 2014. These are highlighted on Figure 3. It is emphasised that this is not the completed construction or irrigation development but it indicates the general command area. The direct impact on Trapaing Thmor is the canal feeding into the northern end of the Reservoir. Construction was ongoing during April 2014 and therefore the canal may be extended to more directly supply the reservoir. It can be deduced that the intention is to provide additional supply to the reservoir which will be distributed via the existing irrigation system. The main right bank canal to the east does not appear to directly supply the existing Trapaing Thmor command area. It is apparent that the Stung Sreng Project will not dramatically increase available water resources since the dry season area has a ceiling of 3,750 ha. However it will increase flexibility to better manage the limited water resources.

Figure 3 Constructed canals for Stung Sreng Water Resource Development Project, April 2014

Source: © Google Earth, 2014

1.5. Misuse and damage to irrigation structures

Soon after installation in 2004 some of the counterweights had been removed from the automatic tilting gates at Irrigation Structure 1. This was instigated by local people because the raised water level had flooded land around the shore of the reservoir. It was also said locally that there was concern about safety of the reservoir embankment because seepage could be seen in places. Another factor is that farmers downstream want water.

By 2008 some of the gates on the culverts had been broken open by farmers to get water to their fields downstream. Gate operating gear has been unbolted from the headwall and gates wedged

Left bank main canal

Right bank main canal

Intakes weir

Canal supplying Trapaing Thmor

Reservoir

High ground

Stung Sreng



open. The farmers did this because they think they will get more water although in reality it makes little difference to the flow and rather wastes water more usefully conserved for the dry season.

The Ou Chambak is being blocked by earth dams. In 2008 it had been blocked divert flow to Culvert No1. Reference to current Google Earth imagery dated 26 April 2014 shows that the Ou Chambak has subsequently been blocked at two further locations upstream. A large flood will breach such dams, or out flank them causing erosion damage to rice fields, but afterwards farmers will rebuild the dams which will continue to impede flow into Trapaing Thmor Reservoir. It is apparent that at present no person or authority, PDWRAM or FWUC is properly controlling operation of Trapaing Thmor Reservoir.

1.6. IUCN Protected Site

The Reservoir is gazetted as the Ang Trapaing Thmor Crane Sanctuary, IUCN (International Union for Conservation of Nature) Category III (natural monument or feature) (see Chapter 4 -3.3.1). The sanctuary was gazetted on 1 January 1999 and covers an area of 10,250 ha. The site covers the open water area of the reservoir and the marginal wetland and grassland to the west and north of the open water.

2. Flood Damage Trapaing Thmor irrigation system was damaged by the flood events of 2013; there was seepage at several locations along the embankment dam and the reservoir slope suffered erosion and wave damage over about 11,000 m. The hoisting system of the automatic gates malfunctioned and the gates did not open automatically. When the gates were opened this released a flood wave downstream which destroyed rice throughout the 35,000 ha command area. Some 291 m of the 8,800 m long main canal MC1 was damaged at five locations and there was also damage to structures. Along the 6,200 m long MC2 some 350 m was damaged at five locations including two locations where rising spindle gate structures suffered damage downstream. For the 4,000 m long MC3 some 316 m was damaged at six locations including two locations where rising spindle gate structures suffered damage downstream.

In addition the downstream end of the 16,400 m Prey Mon Main Canal was damaged over a length of 1,250 m at three locations. This section turns to run parallel to National Road No.6 about 1.1 km south of the road over a distance of 6 km. There are three road bridges along the national highway, all with significant scour downstream which is clear evidence of high discharge. They have a combined catchment about 160 km2 downstream of Trapaing Thmor reservoir which includes the canals and drains of the Trapaing Thmor irrigation system. The embankments along the Prey Mon Canal obstruct this flow and are therefore vulnerable to damage. Provision must be made to pass the flow from the bridges across the canal.

The drainage canals (DC1 and DC2) were also damaged. For the 8,129 m long DC1 1,078 m of bank was damaged at six locations. For the 7,200 m long DC2 were damaged, 1495 m of bank was damaged in eleven locations. Stage 2 repairs under FDERP-AF started for the dam in October 2014 under works package CW01A. They will be continued under works package CW01B, also for works along MC1, MC2, MC3 and Prey Mon canals and DC1 and DC2.

The remaining works for this system will be completed under Stage 3 to assure wet season supplementary irrigation to about 35,000 ha of rice paddy.



Chapter 2 - SUB-PROJECT DESCRIPTION

1. Location Trapaing Thmor can be reached from Siem Reap Town taking the junction off National road No.6 at km 384 and then 22.7 km north and west via Phnom Srok. It can also be approach from via the west via Serey Sisophon.

Trapaing Thmor irrigation system is stated by MOWRAM to command an area of 35,000 ha located five communes in Phnom Srok and Preah Netr Preah districts, Banteay Meanchey Province. There are forty one villages in total from these five communes. The topographic water resource catchment is large extending into Udor Meanchey Province as far as the Thai border.

2. Existing Situation

2.1. Description of Facilities

Trapaing Thmor comprises an embankment dam and reservoir which is used to store and distribute water for supplementary irrigation to 35,000 ha and more limited dry season irrigation. Main components of irrigation infrastructure are summarised by Table 2.

Table 2 Summary of existing irrigation infrastructure at Trapaing Thmor Irrigation System

Length Structures Descriptions

km Head regulator Oxcart bridge Outlet/divider Intake

Embankment dam 18.4 8

Main Canal No.1 8.8 3 3 9



Main Canal Prey Mon 16.4 2 10 9

Drainage Canal No.1 8.129

Drainage Canal No.2 7.2

The dam is a low earth embankment “L” shaped in plan and about 18.4 km long. The reservoir is shallow but large in area; about 11 km2 in the dry season but possibly 50 km2 when at full supply level (FSL).

Along the dam there are three large irrigation structures controlling flow to three main canals. There are seven smaller culverts supplying water to the land not supplied from the main canals. Main canal MC1 also functions as a conveyance canal supplying Prey Mon Canal which irrigates land south of National Road No.6. Main canals MC2 and MC3 irrigate land within the command of the canals. The three main canals also function as drains when the reservoir is spilling. Drains DC1 and DC2 drain the land between the main canals.



Figure 4 Layout of main features of Trapaing Thmor Irrigation System

MC3 MC2 MC1

DC1

DC2

Prey Mon Canal

Prey Mon Canal



2.2. State of Repair

The dam was extensively damaged during the 2013 floods over a length of about 11 km. This is because the reservoir became full with less than 0.5 m freeboard to the dam crest which resulted in erosion and wave damage over much of the reservoir facing slope.

The automatic counterweighted tilting gates are jamming and causing the reservoir to fill to dangerous levels. The gates have had to be forcibly opened. On at least one occasion the bucket on a hydraulic excavator was used to push against the stiffening flanges on the gate pulleys to force them to turn and lower the gate. This caused visible damage to the pulleys which have not been repaired. See the additional discussion which follows below.

The main canals have suffered repeated flood damage. In the case of MC1 when the tilting gates at Irrigation Structure 1 are forcibly or suddenly opened this releases a flood wave at least 33 m3/s, (and much more if the reservoir water level is already above 18.2 m elevation). The bank full capacity of main canal MC1 downstream is less than 16 m3/s. The situation is similar for MC2 and MC3, the canals simply do not have the capacity to function as drains when the reservoir is spilling during large flood events. This clearly explains why damage keeps occurring to the canals. Repairing the canals and modifying irrigation structures will not solve the problem. Alternative, sustainable solutions are required.

2.3. Irrigation Structure 1 Tilting Gates

The gates at Irrigation Structure 1 were installed in 2004 as automatic counter balanced tilting gates designed to open and release water as the reservoir level rises. The counter balance is provided by cables at each end which pass over round pulleys to concrete counter weights at the other end of the cable. As the water level rises and the gate opens, the force on the gate and the moment about the hinge pin changes. The cable running over the pulley is intended to produce a constant resisting force. The proportioning of the force of the water on the gate to the resisting force of the counterweights controls the discharge. But as already mentioned operation of the gates is erratic and unreliable and the gates have at times jammed and when opened suddenly cause a flood wave downstream.

A properly designed counterweight operating system would use an eccentric cam to change the resisting force as the water level rises and the gate opens changing the driving force on the gate. A counterweighted operating system relies on the balance between the resisting and driving forces for the gates to operate properly. The problem with most counterweight operating systems is that the balance changes over time due to corrosion and misalignment of the functioning parts. For the system to operate properly, the balance needs to be adjusted periodically to account for the changes in the resisting forces. The counterweights at this spillway are located in an open cage but rather inaccessible because they hang over the water upstream and are consequently difficult to access to adjust the balance. There is anecdotal evidence that the counterweights were reduced soon after they were installed because fields around the reservoir were flooding but no other information on changes being made has come to light. Counterweight tilting gates are not used for modern spillway gate design because it is too difficult to maintain the balance for dependable operation. This is because of various factors of ageing working in combination including: poor maintenance, lack of lubrication, corrosion and dirt, trash, misalignment, etc..

Several alternatives are available to replace and improve the existing operating system for the spillway gates. The advantages and disadvantages of each alternative are discussed in Chapter 3 -1.3.



3. Socio-economic and Agriculture

3.1. Area

Trapaing Thmor Irrigation System is located five communes in Phnom Srok and Preah Netr Preah districts, Banteay Meanchey Province. There are forty one villages in total from these five communes, with 10,095 households. The total land area for rice cultivation is about 29,546 ha. It is noted that 95% of the population is occupied in rice cultivation, 3% are workers in other employment and 2% are occupied in small family businesses.

Table 3 – Area and population in the target area of Trapaing Thmor subproject

Population Land Area (ha) No Commune

Total Households Total Female Rice Field Cropping Total

1 Paoy Char 2,632 11,448 5,787 4,020 N/A 4,020

2 Srash Chik 1,581 7,056 3,671 3,850 N/A 3,850

3 Ponley 2,917 13,977 6,507 5,710 N/A 5,710

4 Tean Kam 942 4,003 2,123 4,697 N/A 4,697

5 Rohal 2,023 8,702 4,343 11,269 N/A 11,269

Total 10,095 45,186 22,431 29,546 N/A 29,546 Source: Village chiefs and commune chiefs

3.2. Cultivated Area and Beneficiaries

Information on the cultivated area beneficiaries is provided in Table 4. Key people including village chiefs and the commune chiefs expect the command area which is to be irrigated in the target area to be about 18,163 ha (accumulation). Separately, 14,603 ha or equal to 80.4% are cultivated for wet season rice and 3,560 ha or equal to 19.6% are cultivated for dry season rice. Most of dry season rice fields are in Rohal commune, Preah Net Preah district.

Table 4 Area and population in the target areas of Trapaing Thmor subproject

Cultivated Area (ha) Average Rice Yield (T/ha)No Commune

Benefited Families WS DS Total WS DS

1 Paoy Char 1,570 3,750 0 3,750 1.78 3

2 Srash Chik 1,560 3,040 760 3,800 1.5 2.5

3 Ponley 1,254 2,138 0 2,138 2 3

4 Tean Kam 741 3,975 0 3,975 1.7 3.5

5 Rohal 818 1,700 2,800 4,500 1.7 3.5

Total 5,943 14,603 3,560 18,163 1.74 3.1 WS: Wet season, DS: Dry season Source: Local authorities and group discussion

Some 2,790.8 ha or equal to 19.1% of the total wet season rice area is for cultivation of short duration rice, 5,522.6 ha or equal to 37.8% is for cultivation of medium duration rice and 6,289.6 ha or equal to 43.1% is for cultivation of late duration rice.

On the other hand, benefited families have utilized 582 ha of the area used during the wet season for further cropping of dry season rice at the end of wet season rice. This includes 3,560 ha of dry season rice in Srash Chik and Rohal communes which is used for two dry season rice crops a year, early and late dry season. Thus the total cultivated areas for dry season rice is up to 7,702 ha.



Adding 7,702 ha of dry season rice and total cultivated area of wet season rice about 14,603 ha and 500 ha of cultivated area for water melon from wet season rice fields in Paoy Char commune, the total irrigated area of Trapaing Thmor subproject is 22,805 ha.

Some 5,943 households will directly benefit from the subproject. This is 49.9% of all households. The average yield of wet season rice is about 1.74 T/ha and dry season rice is about 3.1 T/ha.

3.3. Agriculture Practices

At the present, the main crops grown in the Trapaing Thmor subproject area are wet season rice, dry season rice and water melon. Rice is broadcast, rainfed and irrigated. Farmers on average use about 100 kg/ha of chemical fertilizer for wet season rice and 200 kg/ha for dry season rice. In the future the use of chemical fertilizer could be increased up to 150 kg/ha for wet season rice and 250 kg/ha for dry season rice.

Rice varieties grown by farmers within the project area have been Phkar Romduol, Phkar Malis and Somaly (fragrant rice) for short duration rice, Phkar Khjey and Torng Sangke for medium duration rice and Sen Kro Oub, Chulsar, Viet Nam (85 days) and IR66 for late duration rice. It is mentioned that a fraction is used as seeds crop and kept by conventional method, so that purity of the rice seed declines over time.

The farmers have done late duration rice before short and medium duration rice in the flooded area in the early wet season to avoid rotten rice with too much water. In general, wet season rice starts at the same time each year from May to June with land preparation and harvesting in November (short duration rice) and December or January (medium and late duration rice) and dry season rice twice a year during the early dry season from November to March and at the end of dry season or early wet season from April to August.

For the future situation with effective irrigation infrastructure there is potential to improve rice productivity. This can be achieved through the System of Rice Intensification to improve soil fertility, rice seed, and water management to increase rice yields.

Based on data from group discussion and the field survey, the average rice yield can be expected to increase from 1.74 T/ha at the present to 2.3 T/ha in the future for wet season rice and from 3.1 T/ha to 4 T/ha for dry season rice. Therefore, with the total area of irrigated rice about 22,305 ha (subtract 500 ha of cultivated area for water melon from 22,805 ha), total rice production of about 49,285 T at the present could be increased up to 64,395 T in the future. This would be a 30.65% increase in rice production over the present day. Detailed information is provided in Table 5.

The farmer community shared with the Consultant Team their suggestions to improve rice production such as:

providing the training on ecological agricultural techniques, especially system of rice intensification, improvement of top soil fertility and rice seed, pest management, fish raising and paddy straw mushroom cultivation;

reconstruction and development of irrigation infrastructure, especially removing the automatic spillway gates and developing a tertiary canal network; and

linking farmer’s rice products to the market (value chain approach).



WS Medium Duration Rice

WS Late Duration Rice

Dry Season Rice

WS Short Duration Rice

Dry Season Rice

Water Melona

Table 5 – Agricultural practices at Trapaing Thmor subproject

Without the project With the project

No Kind of crop Cultivated Area

Yield Total Yield Cultivated Area

Yield Total Yield

ha T/ha T ha T/ha T

1 WS Short duration rice

2,791 1.74 4,856 2,791 2.3 6,419

2 WS Middle duration rice

5,523 1.74 9,609 5,523 2.3 12,702

3 WS Late duration rice

6,290 1.74 10,944 6,290 2.3 14,466

4 DS Early & late dry season rice*

7702 3.1 23,876 7702 4 30,808

5 Water Melon 500 N/A N/A 500 N/A N/A

Totals 49,285 64,395

* Land which is cropped twice each year. Source: Group discussion

3.4. Cropping Patterns

Figure 5 – Existing Cropping Pattern Trapaing Subproject

Month Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar

Source: Group discussion

3.5. Agricultural Product Marketing

It can be seen that the average size of rice field for each household is about 3 ha, so that they have potential to produce paddy rice for selling to the market. For the existing situation (without the project), all the benefiting households have sold 4.5 T of paddy rice for a price of US$0.225/kg or US$225/T for mixed paddy, US$0.30/kg or US$300/T for fragrant paddy and US$0.20/kg or



US$200/T for dry season rice. Discussion with the farmers gave consensus for the future situation that after irrigation infrastructure is provided the amount of paddy rice sold could increase from 4.5 T/family to 6.5 T/family. Thus, farmers could expect to increase gross income from US$1,091 per family at the present to US$1,576 per family at the future from the sale of paddy rice per year.

The possible markets for the paddy rice are local millers at district or provincial markets. Most agriculture products especially paddy rice were sold through assisted collection by village agencies or middlemen who come from in and outside the village before selling to rice mill owners. Even though the market price for paddy rice has increased in recent time compare to previous time the farmers still get a low price. If rice farmers can sell directly to rice millers, the price they get will be increased.

Table 6 Without the project crop budget and gross margin

Crop Area Yield Total of yield

Price Gross financial revenue

Cost Gross cost

Net income

ha T/ha T US$/T US$ US$/ha US$ US$

WS Short duration rice 2,791 1.74 4,856 300 1,456,798 360 1,005,037 451,761

WS Middle duration rice 5,523 1.74 9,609 225 2,162,098 353 1,947,407 214,691

WS Late duration rice 6,290 1.74 10,944 225 2,462,378 353 2,217,870 244,508

DS Early & late dry season rice* 7,702 3.1 23,876 200 4,775,240 587 4,519,149 256,092

Water Melon 500 0 875,000 1,250 625,000 250,000

Total 1,417,052

* Land which is cropped twice each year. WS=Wet Season, DS=Dry Season, TP=Transplanted, BC=Broadcast

Table 7 – With the project crop budget and gross margin

Crop Area Yield Total of yield

Price Gross financial revenue

Cost Gross cost

Net income

ha T/ha T US$/T US$ US$/ha US$ US$

WS Short duration rice 2,791 2.3 6,419 300 1,925,652 393.63 1,098,529 827,123

WS Middle duration rice 5,523 2.3 12,702 225 2,857,945 386.13 2,132,414 725,532

WS Late duration rice 6,290 2.3 14,466 225 3,254,868 386.13 2,428,572 826,296

DS Early & late dry season rice* 7702 4 30,808 200 6,161,600 631.00 4,859,962 1,301,638

Water Melon 500

1,000,000 1,250 625,000 375,000

Total 4,055,589

* Land which is cropped twice each year. WS=Wet Season, DS=Dry Season, TP=Transplanted, BC=Broadcast



3.6. Economic Internal Rate of Return

The capital investment for damage repair of the irrigation system infrastructure is assumed to be US$ 7,490,639. In the future, upon completion of the works, it is anticipated that the crop yield of paddy rice will be increased and to provide more income than previously for the beneficiaries. Based on field data the net value added for the whole area of the irrigation system without the project is about US$1,417,052 and it is anticipated that the net value added will increase to US$4,055,589 (returned net profit). So this would provide a net profit of about US$ 2,638,538 for each year.

The Economic Internal Rate of Return (EIRR) discounted over five years at 12% is calculated to be 15.3% as detailed in Table 8.

Table 8 – Economic Cash Flow at Trapaing Thmor subproject

Year Capital Costs

O&M costs (a)

Engineer- ing &

services

Income foregone for land losses

Total costs

Phased increment-

al crop benefits (b)

Total Benefits

Net benefits

US$ US$ US$ US$ US$ US$ US$ US$

1 7,490,639 Nil Nil Nil 7,490,639 -7,490,639

2 Nil Nil Nil Nil 2,638,538 2,638,538 2,638,538

3 Nil Nil Nil Nil 2,638,538 2,638,538 2,638,538

4 Nil Nil Nil Nil 2,638,538 2,638,538 2,638,538

5 Nil Nil Nil Nil 2,638,538 2,638,538 2,638,538

EIRR 15.3%

ENPV $467,430

B/C ratio 1.20 Discount Factor: 12%

4. FWUC/FWUG

4.1. FWUC History and Establishment

The process to establish Trapeang Thmor Reservoir FWUC started on 11 June 2004. The process was carried out with the cooperation and participation of MOWRAM and PDOWRAM Banteay Meanchey Province, the local authorities, and the farmer beneficiaries. The process was carried out according to declaration No.306 and No.001 of the RGC. At that time the irrigation system had just been rehabilitated by MOWRAM with assistance from JICA.

The Draft Statute and By-laws and the Internal Regulations, were finalised on 7 March 2005. These are set out in eight Chapters and 40 Articles notably Chapter 1: Name and Objectives, Chapter 5: The Revenue, Expenses and Audit of the FWUC, Chapter 7: Punishment, Article 24: stating the principle of paying the irrigation service fee (ISF) and the Article 37: Penalties for activities considered against the interests of the FWUC and the levels of fines are determined. The FWUC committee was elected on 4 May 2005. The FWUC establishment and development process was implemented according to the MOWRAM principles of Participatory Irrigation Management and Development (PIMD) from Step 1 to Step 8.

Certificate No.113 of Management Authority for Trapeang Thmor FWUC was registered by MOWRAM on 3 January 2006. The Certificate is useful in order to clarify and make official public



recognition that the FWUC has the responsibility and authority to oversee management of the irrigation system.

4.2. FWUC Membership List

The name of the FWUC for Trapeang Thmor scheme is Ang (Reservoir) Trapeang Thmor Irrigation System Farmer Water User Community (Ang Trapeang Thmor FWUC). The FWUC committee has 24 members. The FWUC Chairman was Mr. Chhoy Kam (089 89 78 31), but recently he has been called to resign, due to the multiple internal problems that have forced him to drop his FWUC responsibilities.

A detailed classified list of land owners and beneficiary farmers in each village was not made in 2006. The landholding and service area lists were drafted but not finished.

During meetings between the national FWUC expert and FWUC Committee, village leaders and commune chiefs during the second week of October 2014 it was stated that the FWUC covered approximately 18,163 ha and had 5,943 farmer household beneficiaries.

There is no fee for membership of the FWUC. The FWUC Office was built following Registration with MOWRAM in 2006 complete with office equipment and stationary (Figure 6).

There are five farmer water user groups (FWUG) with ten farmer water user sub-groups (FWUS-G). The organizational structure is shown by Figure 7 and the membership, positions and responsibility of various committees by Table 9 and Table 10.

Figure 7 Organization of Trapaing Thmor FWUC

Selection of the FWUC committees was by election from the bottom (from grassroots level) to the top by village representatives, and then election for the FWUGs and FWUC committee. Fundamental democratic principles were followed to ensure freedom and equality in the election

Figure 6 Ang Trapaeng Thma FWUC Office

Farmer Water User Communty

FWUG I

FWUS-G 1

FWUS-G 2

FWUG I FWUG I FWUG I FWUG I

FWUS-G 1 FWUS-G 1 FWUS-G 1 FWUS-G 1

FWUS-G 2 FWUS-G 2 FWUS-G 2 FWUS-G 2



process. Advisors were the Phnom Srok and Preah Netr Preah District Governors. The Roles of the FWUC Advisory Group is to work with the FWUC Management Committee (FMC) and oversee the operation of the FWUC and FMC to ensure compliance with regulations and policy, and to assist and support the FMC in dealing with the more difficult member administration problems that require the use of authority, such as delinquent FWUC members, and in organizing and mobilizing reluctant FWUC members as needed for O&M and payment of ISFs.

Table 9 – Trapaing Thmor FWUC Committee

I – Trapaing Thmor FWUC Committee

No. Name Position Responsibility

1 Mr Chhoy Kam Chief Overall management

2 Mr Suy Lek 1st Vice Chief Planning, maintenance and repair

3 Mr Ros Vuy 2nd Vice Chief Water distribution

4 Mr Chhom Chhing Treasurer Budget management

5 All FWUGs chiefs are members with responsibilities of the FWUC and 2nd Vice Chief assistants

II – Assistants to Trapaing Thmor FWUC Committee

1 All FWUGs who have responsibilities the same as the 2nd Vice Chief

2 Assistant to the 2nd Vice Chief

Mr Ouk Phak

Mr Mork Thai

Mr Tuy Chhame

Mr Roeung Soeun

3 Core farmer organizer

Mr Chhagn Ley

Mr Klok Louck

III – Advisors to Trapaing Thmor FWUC Committee

1 Phnom Srok District Governor

2 Pouy Char Commune Chief

Table 10 Trapaing Thmor FWUGs Committees

IV – Trapaing Thmor FWUG Committees

No. Name Position No. Name Position

I FWUG I has 2 FWUS-G IV FWUG IV has 2 FWUS-G

1 Mr Nap Sameth Chief 1 Mr Ros Vuy Chief

2 Mr Norm Savoet 1st Vice Chief 2 Mr Ouk Phat 1st Vice Chief

3 Mr Pen Sambok 2nd Vice Chief 3 Mr Ros Mouy 2nd Vice Chief

4 Mr Dy Tiv Treasurer 4 Mr Him Houy Treasurer

I.1 FWUS-G No.1 IV.1 FWUS-G No.1

1 Mr Pen Sambok Chief 1 Mr Ouk Phak Chief

2 Mr Dy Tiv 1st Vice Chief 2 Mr Him Huy 1st Vice Chief

3 Mr Chok Sarou 2nd Vice Chief 3 Mr Chhem Chhome 2nd Vice Chief

4 Mr Chhav Cham Treasurer 4 Mr Nork Seam Treasurer



IV – Trapaing Thmor FWUG Committees

No. Name Position No. Name Position

I.2 FWUS-G No.2 IV.2 FWUS-G No.2

1 Mr Nap Sameth Chief 1 Mr Y Roeut Chief

2 Mr Norm Savoet 1st Vice Chief 2 Mr Ros Mouy 1st Vice Chief

3 Mr Khut Khugn 2nd Vice Chief 3 Mr Hing Chhat 2nd Vice Chief

4 Mr Sean Chom Treasurer 4 Mr Tot Chhoeub Treasurer

II FWUG II has 2 FWUS-G V FWUG V has 2 FWUS-G

1 Mr Chhorn Chhign Chief 1 Mr Klot Luch Chief

2 Mr Mork Thai 1st Vice Chief 2 Mr Thoung Than 1st Vice Chief

3 Mr Ourn Bun Chhoeu 2nd Vice Chief 3 Mr Neb Chhum 2nd Vice Chief

4 Mr Chav Chath Treasurer 4 Mr Smorn Cheam Treasurer

II.1 FWUS-G No.1 V.1 FWUS-G No.1

1 Mr Torn Hoeut Chief 1 Mr Roeung Soeun Chief

2 Mr Men Vong 1st Vice Chief 2 Mr Thoung Than 1st Vice Chief

3 Mr Kone Sa 2nd Vice Chief 3 Mr Neb Chhum 2nd Vice Chief

4 Mr Chea Muy Treasurer 4 Mr Kong Mary Treasurer

II.2 FWUS-G No.2 V.2 FWUS-G No.2

1 Mr Thy Thoeun Chief 1 Mr Smorn Cheam Chief

2 Mr Sem Samm 1st Vice Chief 2 Mr Soeum Pheap 1st Vice Chief

3 Mr Kean Sem 2nd Vice Chief 3 Mr Ros Roeun 2nd Vice Chief

4 Mr La Rorng Treasurer 4 Mr Mann Yeth Treasurer

III FWUG III has 2 FWUS-G

1 Mr Nap Sameth Chief

2 Mr Norm Savoet 1st Vice Chief

3 Mr Pen Sambok 2nd Vice Chief

4 Mr Dy Tiv Treasurer

III.1 FWUS-G No.1

1 Mr Pen Sambok Chief

2 Mr Dy Tiv 1st Vice Chief

3 Mr Chok Sarou 2nd Vice Chief

4 Mr Chhav Cham Treasurer

III.2 FWUS-G No.2

1 Mr Nap Sameth Chief

2 Mr Norm Savoet 1st Vice Chief

3 Mr Khut Khugn 2nd Vice Chief

4 Mr Sean Chom Treasurer



The position on FWUC membership is unclear; the process appears only partially complete. Only some of the farmer members have completed the application form and returned it to the FWUC. Completed applications show the head of family name, sex, age, current address, cropping land area and kind of crop grown. The thumb print of the addressee and FWUC signature with stamp are needed to validate the application form (Figure 8).

Meetings were held by FWUC board, with the main agenda on to explain the statute to each beneficiary village. The FWUC procedures were explained by reading out each paragraph of the Article to the meeting. Such meetings were convened during 2010 and 2011 and sometimes presided over MOWRAM and PDOWRAM technical teams, district governors, local authorities and other organizations involved. There have been no measures, punishments or penalties against members of the FWUC who did not attend the meetings; they were simply advised to attend the next meeting.

4.3. FWUC Management of Trapaing Thmor Reservoir

The FWUC does not prepare an annual budget plan because the ISF collection rate is so low that there are insufficient funds for maintenance. Thus the FWUC is mostly confused and has effectively collapsed. There are no rewards or salary or allowance paid to any of the FWUC committee or collectors. In 2010, MOWRAM deposited US$500 into the Ang Trapeang Thmor FWUC Bank Account at ACLEDA Bank Plc. in order to contribute to the ISF collection of the scheme for small maintenance works. But after expenses were paid for FWUC operating expenses such as gasoline and motor repairs, compounded by the low ISF collection rate, the fund was exhausted before any maintaining could be done.

The procedures for ISF collection are that the FWUC in cooperation with the village chiefs, representative of villages and a representative of the Commune Council give advance notice of ISF collection. According to the notified schedule ISF collectors go directly to beneficiary farmers’ home in the village. The collectors give back a receipt to the beneficiary farmers in the scheme (Figure 9). An expenses allowance is paid to the ISF collectors around 10% of the total amount of ISF collected in Sub-Group or block, this is to pay for gasoline motorbike costs. The reason given for the low ISF collection rate is the many flood years. Some farmers are travelling to Thailand for work because they cannot subsist from their farms. Farmers in debt to the FWUC are required to clear the debt by double payment of the ISF the next year. Unfortunately, because of flood years in 2011 and 2013 farmers lost crops and they have not been able to pay the ISF. Some ISFs

Figure 8 FWUC Membership application form

Figure 9 Sample BANK and ISF receipts



have been collected for plots growing water melon and dry season rice but the small amount of money is not enough for the small system repairs.

4.4. Tourism Site

The large body of open water means that Trapaing Thmor Reservoir has long been a recreational area for the local population. Now with good road access it attracts day visitors from surrounding provinces, and international visitors also.

Most activity is focused on the food stalls and restaurants at the south east corner of the reservoir and MC1. This is because of the easy access by road and to the reservoir shore, the open view across the water to distant hills, often with a cooling breeze.

The reservoir is an ancient wetland and the west and north shores in particular are unpopulated with abundant grassland and marginal aquatic species which thrive on the seasonal fluctuation in water level. The site is gazetted as the Ang Trapaing Thmor Crane Sanctuary, IUCN (International Union for Conservation of Nature) Category III (natural monument or feature). The sanctuary was gazetted on 1 January 1999 and covers an area of 10,250 ha. The reserve was set aside to protect the rare Eastern Sarus Crane (Grus antigone sharpii). Prior to the discovery of the crane at Trapaing Thmor, there were thought to be fewer than 1,000 of the birds left alive in the world. The sanctuary is also an important conservation area for a number of other threatened species. One globally threatened primate species, the Long Tailed Macaque is found within the sanctuary. One globally threatened ungulate species, the Eld's Deer and three globally threatened turtle species, the Asian Box Turtle, the Malayan Snail Eating Turtle and the Elongated tortoise. However, the current status of these populations is not known.

Tourism related business is focused on day visitors, there are no tourist hotels. There can be around 50 to 60 permanent and mobile kiosks or food sellers peaking during ceremonies, festivals or special days. The authorities representing the Commune, village or police collect money from the businesses as tax and for provision of security. In general, one permanent restaurant must pay US$125.00 per year. The Department of Tourism, PDWRAM Banteay Meanchey Province and the FWUC Committee are not involved with this taxation collection.

4.5. Conclusion

Although the FWUC has been registered with MOWRAM since January 2006, the FWUC Committee still has no real farmer beneficiary member list. This means that ISF collection has been done in the wrong way outside of the FWUC statute. The ISF is collected for the maintenance of the irrigation system. The poor collection rate which was achieved meant that within only one or two years after construction inadequate maintenance was causing accelerated deterioration of the system. In addition, the farmer members have misunderstood the objectives and limitations of the irrigation system. The major reason why farmers refused to pay the ISF is because they do not get enough water in the dry season. They do not understand that that the reservoir cannot store enough water for dry season irrigation to the whole command area. The irrigation system can only supply supplementary irrigation to the full command area during in the wet season but only a fraction of this area during the dry season limited by the available water resource in the reservoir.

The situation is made much worse by the fundamental deficiencies in the irrigation system already discussed specifically, but not limited to: the unsuitable gates and the fact that the main irrigation canals are too small to function as drains when the reservoir is spilling. Farmers have seen so many failures to deliver it is not surprising they are reluctant to pay ISF.



An essential step to reviving the FWUC and to achieving full ISF collection is to make sure that farmers understand that the scheme provides supplementary irrigation for all but that dry season irrigation can only be provided to groups of fields. Currently most dry season irrigation is at the downstream area of the system south of National Road No.6 rather than land closest to the reservoir. This is a direct consequence of the Khmer Rouge era canals which never achieved successful irrigation rather they created drought at the upstream end of the system and water logging at the downstream end. It would be both clearer to farmers and more equitable to separate the ISF for wet and dry seasons; all farmers would pay the wet season fee but only farmers who received water during the dry season would be charged the dry season fee.

But farmers would still refuse to pay the ISF if the service is poor. Therefore the irrigation and flood management infrastructure must be robust and effective to ensure that the FWUC can provide the membership with the service which is promised. The importance of effective flood management cannot be underestimated. The low lying land at Trapaing Thmor floods every year and rice can be grown. What the irrigation system has to do is remove the risk of seasonal variations because of drought and flood. There must be no uncontrolled release from the reservoir; gates must be operated correctly, at the right time, and at all times under control. The system must be monitored and patrolled. Reckless anti-social activities such as vandalising irrigation structures, blocking water channels and breaking down banks must be vigorously controlled.

Proper water management, operation and maintenance of irrigation systems will allow farmers to increase rice production. It will contribute to building trust between the FWUC and the farmers in the leadership, accountability and transparency. If the farmers can see real benefit then the ISF collection rate can be kept above the threshold to maintain the system.

As is common practice in Cambodia some fraction of the tourist revenue should be fed back to the FWUC. Normally this is from fees on tourism businesses collected through the Department of Tourism.

5. O&M The discussion at Chapter 2 -4 above explains that although the FWUC is not undertaking maintenance the local authorities and PDWRAM Banteay Meanchey Province at least participate in emergency operation of the irrigation system. Since the 2011 flood a member of MOWRAM staff is stationed at the reservoir each flood season from July to November. He is supported by PDWRAM Banteay Meanchey Province. This is to ensure prompt response to any emergency situation including operation of reservoir gates.

Water for irrigation is released from the reservoir via the vertical lift sluice gates. Water is then distributed to the fields via the numerous distribution structures and similarly drained away for harvest.

Dry season irrigation is mostly practices south of National Road No.6 along the Prey Mon canal.

5.1. Hydrology

A detailed discussion of hydrology is presented at Appendix 1.

The hydrological studies identified a number of issues which need to be addressed to ensure flood resilience and sustainability of the Trapaing Thmor Irrigation System including:



During the 2013 the reservoir surcharged which reduced the dam freeboard to 0.6 m which is inadequate.

When the reservoir is spilling the flows passing to main canals MC1, MC2 and MC3 exceed the capacity of the canals. Water will overtop canal banks. If there is an embankment such as a road this will be overtopped with potential for breaching.

Increasing the spillway capacity would increase damaging flow to main canals MC1, MC2 and MC3, it is better to manage the live reservoir storage to protect the canals.

The 6 km of Prey Mon canal which runs parallel to National Road No.6 is embanked and obstructs large flows downstream from three road bridges.

Recommendations for additional works to address these and other problems are presented at Chapter 3 -1.2.3.

In terms of water resources the hydrological studies have also assembled reasonable rainfall data. There is however no information on reservoir inflows. Therefore, estimates have been derived from the observed flows for the Stung Sreng at Kralanh as presented in the Water Resources Management Sector Development Program 20148.



Chapter 3 - SCOPE OF WORKS

1. Proposed Interventions

1.1. Stage 2 Civil Works

The works currently being constructed under Stage 2 to the value US$1.5 million and for completion 31 January 2015 are: Installation of a clay cut-off trench at the earth embankment dam to control seepage over a

length 3,500 m. Installation of gabion mattress and gabion boxes on the reservoir slope of the embankment

dam as wave protection over a length 3,000 m. Restoring the embankment dam crest level and provision of Laterite pavement over a length

3,000 m.

1.2. Stage 3

1.2.1. NCB Contract

Tenders have been invited for works to an estimated value US$1.0 million. The closing date for bid submission was set as 16 December 2014. The works comprise: Installation of a clay cut-off trench at the earth embankment dam to control seepage over a


dam as wave protection over a length 1,500 m. Restoring the embankment dam crest level and provision of Laterite pavement over a length

7,400 m. Repairs to main canals MC1, MC2, MC3 and MC Prey Mon, beds, banks and damaged

structure over a length 957 m. Repairs to main drains DC1 and DC2, beds, banks and damaged structure over a length

2,573 m.

1.2.2. ICB Contract

The balance of the Stage 3 works has an allocated budget from the PP of US$5.0 million and because of the value must be procured by ICB. The works will comprise completing repairs to the dam and irrigation system as follows: Installation of a clay cut-off trench at the earth embankment dam to control seepage over a


dam as wave protection over a length 6,100 m. Provision of a wave wall to the dam crest over a length 7,000 m. Restoring the embankment dam crest level and provision of Laterite pavement over a length

10,600 m.



Repairs to main canals MC1, MC2, MC3 MC Prey Mon, beds, banks and damaged structure over a length 5,700 m.

Galvanised 60 mm diameter steel tube handrail, length 220 m at irrigation structure. Slope protection both banks downstream of: Irrigation Structure 1, length 142 m; Irrigation

Structure 2, 139 m; and Irrigation structure 3, 186 m. Provision of multiple cell inverted siphons to pass drainage flows from National Road No.6

bridges beneath the Prey Mon canal, beneath irrigation canals, 3 No. Extension of gated structures on main canals to increase capacity when the canals are

operating as drains for reservoir spill, MC1 3 No, MC2 2 No, MC3 2 No, and MC Prey Mon 1 No.

Renovation of concrete slab for surfaced area adjacent to FWUC building and upstream side of Irrigation Structure 1.

Solution to the malfunctioning automatic counterweighted tilting gates at Irrigation Structure 1. Replace the hoisting at head regulators 1 no, and Irrigation Structure 5 No.

1.2.3. Additional Works Recommended

There are several fundamental problems with Trapaing Thmor which need to be addressed under the responsibility of MOWRAM, in the future where they cannot be resolved within the scope of FDERP-AF. Refer to Appendix 1 for explanation of issues. Specific issues are: When the reservoir is spilling the flows passing to main canals MC1, MC2 and MC3 exceed the

capacity of the canals. Maximise the capacity of the canals and provide long reinforced grass side spillways to allow excess discharge to go into bank storage and to prevent direct damage to crops.

Manage the reservoir live storage to protect the canals and fields downstream from damage caused by spillway discharge.

Provide a hydromet station to monitor and record reservoir levels in real time. The automatic gates did not open automatically during the 2011 and 2013 floods. Replace the

gates with a fixed crest weir and two new 2.0 m wide vertical lift sluice gates.

1.3. Automatic Tilting Gates

The operation of the existing gates has been described at Chapter 2 -2.3. During a large flood event it makes little difference whether the gates are opened or closed. This is why replacement with weirs and a pair of small gates is recommended at 1.2.3 above.

However, alternatives means of operation have been considered if the gates are retained. Modern operational systems including electrically driven wire rope hoists and hydraulic rams were investigated. MOWRAM prefers a hand operated wire rope hoist fitted to one gate. This will require a custom design and manufacture.

2. Cost Estimate The Contract Sum for the Stage 2 DC works package CW01A is US$1,499,961 including 5% contingency. The works are ongoing and due for completion 31 January 2015. The works are being carried out under a remeasurement contract, the final Contract Price will be known after final measurement and any variations to the works.



The balance of the Stage 2 budget US$1.0 million will now be expended under Stage 3 through NCB works package CW01B for which the tendering process is ongoing with bids returned 16 December 2014.

The PP estimate cost for Stage 3 works is US$5.0 million. An initial estimate for the work designed to date is US$4.2 million but this provides scope to include the improvements recommended above. The Engineer’s estimate will be prepared upon completion of the final design. The scope of works will be adjusted to match the PP budget.

3. Photographs The following selection of photographs show conditions during the 2013 flood, examples of the flood damage, and ongoing Stage 2 works to repair and improve flood resilience of the dam.

Military making emergency repairs to dam 2013 Flow at Irrigation Structure 1 during 2013 flood

Flow from Irrigation Structure 1 into MC1 during 2013 flood Flow from Irrigation Structure 3 into MC3 during 2013 flood

Breached bank of MC2 during 2013 flood Damage around structures along MC3 during 2013 flood



Cross drainage flow at Prey Mon canal during 2013 flood Breached bank of DC1 during 2013 flood

Washout of backfill at DC2 structure during 2013 flood Wave and erosion damage to dam in March 2013

MC2 downstream of Irrigation Structure 2, March 2014 MC3 downstream of Irrigation Structure 3, March 2014

Washout of backfill around structure on MC1, March 2014 Washout of backfill around structure on MC1, March 2014



Compacting clay cut-off trench Stage 2 works, October 2014 Gabion mattress wave protection Stage 2 works October 2014



Chapter 4 - SUB-PROJECT SCREENING

1. General and Irrigation Specific Screening

1.1. Stage 2

The subproject satisfied the screening requirements for Stage 2 work. The completed Assessment and Confirmation Sheet for the Stage 2 works as per Table A1-1 of the Project Administration Manual (PAM) are at Appendix 3.

1.2. Stage 3

Acceptance of Stage 2 works means that the subproject met the General Selection Criteria for selection of subprojects set out in Appendix 1, Item 1 of the PAM. This Subproject Profile confirms that the General Selection Criteria is satisfied.

The screening of additional criteria for irrigation, Appendix 1, Item 4 of the PAM is shown at Appendix 4.

2. Safeguards Screening: Resettlement

2.1. Scope of Land Acquisition and Resettlement

There is no evidence of involuntary resettlement impact from the proposed Stage 3 reconstruction. The Stage 3 works are repairs and improvements to existing embankment dam, irrigation canals, drains, access roads and structures. No new works locations will be introduced. There is no land encroachment by the villagers. However, there will be some small structures such as stalls and shelters to be found in the Right of Way for Stage 3 works. No land acquisition is required for this subproject intervention. In short, there is no involuntary resettlement impact found at this pre-detailed design stage from the proposed rehabilitation to the Main Canal scheme.

2.2. Resettlement Impact Categorisation Check-list

The resettlement impact check-list is included in Appendix 5 and confirms that there are no involuntary resettlement impacts and that the project interventions are within the Category C for resettlement as per the Safeguard Policy Statement (ADB’s SPS. 20091).

The screening for resettlement categorization was conducted from the 6 to 10 October 2014 by the national resettlement specialist accompanied by other team members including design engineers, socio-agricultural economist, FWUC specialist and environmental specialist.

Initial screening for involuntary resettlement is to be revisited following detailed design.



2.3. Voluntary Resettlement

Although no involuntary resettlement was identified at this pre-design stage, there will be voluntary resettlement due to some villagers who have built wooden structures such as stalls, shelters and fences. Some farmers have been growing rice and perennial crops inside the rights of way of during the wet season and also as a result from the participatory irrigation design process whereby the beneficiaries discuss and agree to their requirements for rehabilitation of the canal during subproject formulation. Based on the ADB requirements put forward in the Resettlement Framework a separate Categorization Report will therefore be necessary, and voluntary donations will also need verification by an independent reviewer should this subproject go ahead. The ADB requirements are included Appendix 4.

2.4. Suggested Follow-up Activities

1 Identify communities to be affected.

2 Determine the impacts of land and asset acquisition on the people and communities affected taking social, cultural, and economic parameters into account.

3 Identify gender and resettlement impacts, and the socioeconomic situation, impacts, needs, and priorities of women.

4 Conduct public consultation with potentially affected people to disseminate project and resettlement information during project design and preparation for engaging stakeholders.

5 Prepare contribution/donation form and collaborate work with local authorities to negotiation with Affected Persons.

3. Safeguards Screening: Environment The objective of environmental screening is to identify and assess potential impacts arising from the subproject implementation on social and natural environments and pollution, and to recommend measures to avoid and mitigate adverse impacts.

3.1. Environmental Assessment Check-list

The potential issues, concerns and impacts identified from the rapid environmental assessment using the ADB Rapid Environmental Assessment Checklist are listed below. Appendix 7 presents the completed checklist.

3.2. Beneficial impacts

The proposed subproject will have beneficial impacts including: (i) the improved agricultural productivity; (ii) improved access roads along the canal; and (iii) as outcomes, improved living standards of local beneficiaries.

Overall, the subproject will significantly contribute to a qualitative improvement in the lives of residents through the increase in agricultural productivity in the subproject area.



3.3. Potential Negative Environmental Impacts

3.3.1. Protected Sites

The Reservoir is gazetted as the Ang Trapaing Thmor Crane Sanctuary, IUCN (International Union for Conservation of Nature) Category III (natural monument or feature). The sanctuary was gazetted on 1 January 1999 and covers an area of 10,250 ha. The site covers the open water area of the reservoir and the marginal wetland and grassland to the west and north of the open water. The reserve was set aside to protect the rare Eastern Sarus Crane (Grus antigone sharpii) but the sanctuary is also an important conservation area for numerous species including other threatened species.

As is quite often the case the habitat which attracts the Sarus Crane and other wildlife is man made, in this case an operational reservoir. Therefore the welfare of the protected area depends in large part on the continued operation of the reservoir. The Sarus Crane is not migratory. Daily movements are between the night roost, foraging sites and daytime roosts. They avoid people and therefore probably do not venture beyond the unpopulated shore areas and don’t travel to the dam.

It is concluded that the construction works on the dam and downstream, all of which has been ongoing over many years, will have no impact on the Sarus Crane or protected area.

3.3.2. Siting concerns

The works are repairs and improvements to the existing embankment dam, irrigation canals, drains, access roads and structures. No new works locations will be introduced. Therefore there are no siting concerns.

3.3.3. Water User Conflicts

There is a pre-existing conflict (since 2004) between farmers upstream of the reservoir who suffer flood damage to crops at FSL and farmers downstream who require water storage for dry season irrigation. Currently the community manages the situation by releasing water from the reservoir when upstream farmers complain. The project will not remove the conflict but improvements to the gates and a clear O&M plan will mitigate the problem.

3.3.4. Salinity

There is an existing problem with salinity in areas of the subproject. This has been caused by seepage from canals, over irrigation and poor drainage. The subproject will mitigate the problem by improvements to canal and drains and providing an O&M Plan for better water level management.

3.3.5. Construction impacts

Potential environmental impacts during the construction phase can have negative effects on the environment and local residents unless properly managed. Environmental impacts associated with the construction phase are as follows



Environmental concerns related to worker camp

The contractor has to establish a camp to provide on-site accommodation to workers, drivers, technicians and other personnel for the duration of the rehabilitation works. Parking lots for heavy construction machinery and a maintenance area may also be required. Depending on the total number of persons and equipment, the duration of the construction and the location of the camp, the environment may be adversely impacted in a number of ways by the presence of the camp and the activities that take place: pressure on available water resources during the dry season, pollution by fuel, engine lubricants, and wastewater.

Impacts on air quality

Dust/suspended particles, noise, gas emissions and vibration will be generated from construction activities, practices and materials. Dust and noise will be more salient during the construction period. These issues and impacts will be temporary but, if not mitigated, will have potentials to result in long-term consequences to the health of the affected communities and the construction workers.

3.4. Environmental Category

The proposed subproject is not environmentally critical. It has no potential to impact on the IUCN Category III protected site. The subproject is therefore assessed as Category B (see sidebox ‘Environment Categorization’ below). The works are repairs and improvements to the existing embankment dam, irrigation canals, drains, access roads and structures. No new works locations will be introduced. No activity will have long term impacts to environmental health and will have socio-economic benefit to the community. The few adverse direct impacts during construction are expected to be localised and will be temporary and short-term, most likely to occur during the peak construction period. These will not be sufficient to threaten or weaken the surrounding resources.

3.5. Environmental Management Plan

The full implementation of the Environmental Management Plan (EMP) by the works contractor will ensure that adequate protection measures are in place to avoid or mitigate the subproject impacts. The requisite EMP has been prepared and is attached Appendix 8.

The general EMP is included as part of the Special Provisions of the Specification and Performance Requirement (ICB documents for FDERP-AF procurement contracts for civil works). The works contractor will incorporate the EMP into his planning and site control and will be required to prepare an EMP for the works and report periodically.



Environment Categorization

The ADB uses a classification system to reflect the significance of a project’s potential environmental impacts. A project’s category is determined by the category of its most environmentally sensitive component, including direct, indirect, cumulative, and induced impacts in the project’s area of influence. Each proposed project is scrutinized as to its type, location, scale, and sensitivity and the magnitude of its potential environmental impacts. Projects are assigned to one of the following four categories:

Category A: A proposed project is classified as category A if it is likely to have significant adverse environmental impacts that are irreversible, diverse, or unprecedented. These impacts may affect an area larger than the sites or facilities subject to physical works. An environmental impact assessment is required.

Category B: A proposed project is classified as category B if its potential adverse environmental impacts are less adverse than those of category A projects. These impacts are site-specific, few if any of them are irreversible, and in most cases mitigation measures can be designed more readily than for category A projects. An initial environmental examination is required.

Category C: A proposed project is classified as category C if it is likely to have minimal or no adverse environmental impacts. No environmental assessment is required although environmental implications need to be reviewed.

Category FI: A proposed project is classified as category FI if it involves investment of ADB funds to or through a FI.



Chapter 5 - CONCLUSIONS

1. Screening The Trapaing Thmor Irrigation System subproject works are not new construction. Stage 3 works will fully restore the function of the irrigation system damaged by floods in 2011 and 2013. The works will improve flood resilience. The restored irrigation system will provide the conditions to have full community participation payment of ISF for the existing registered FWUC. This will further enhance sustainability of the irrigation system.

One third of the works was originally reviewed and accepted to satisfy the General Selection Criteria for Stage 2 although only 20% actually proceeded at that stage. The General Selection Criteria has been reviewed for the Stage 3 works during preparation of this subproject profile which confirms that they are still satisfied.

The screening for additional criteria for irrigation, Appendix 1, Item 4 of the PAM, March 2014 is shown at Appendix 4 of this subproject profile, together with requirements from the Report and Recommendations of the President (RRP). Trapaing Thmor Irrigation System subproject is deemed to satisfy all selection criteria.

No involuntary resettlement impacts have been identified and the subproject interventions are within Category C for resettlement.

Trapaing Thmor Irrigation System is situated in a protected area. The Reservoir is gazetted as the Ang Trapaing Thmor Crane Sanctuary, IUCN (International Union for Conservation of Nature) Category III (natural monument or feature) (see Chapter 4 -Chapter 4 -3.3.1). The sanctuary was gazetted on 1 January 1999 and covers an area of 10,250 ha. The site covers the open water area of the reservoir and the marginal wetland and grassland to the west and north of the open water. However works will only be executed around the boundary of the protected area, specifically the dam. Precedent has been set because works have been undertaken on the dam since 2004 with no negative impact on the protected area. Indeed the habitat of the protected area is dependent on the man-made feature which is the reservoir. No negative impacts are foreseen for the protected area. Overall the subproject proposals will have minimal or no adverse environmental impacts. Short-term environmental impacts may occur during the construction phase.

Average repair costs will amount to about UD$214/ha of gross area (agricultural lands) which is within the acceptable ceiling of US$2,000/ha§. Furthermore, the EIRR is calculated to be 15.3% which is greater than the minimum EIRR of 12% required by the PAM and paragraph 23 of the (RRP)**.

§ PAM March 2014, Appendix 1, Item 4 (viii).

** RRP April 2014, III. Due Diligence, A. Economic and Financial, paragraph 23.



2. Proposed Interventions The proposed subproject interventions for civil works are described at Chapter 3 -1. The work a clay cut-off trench, gabion wave protection and a wave wall at the dam. There will be modification to the gates and weirs at irrigation Structure 1 and possibly Irrigation Structure 2, both of which are located on the dam. The remainder of the works will comprise repairs to main canals, main drains and appurtenant structures, some structures will be modified and extended and new inverted siphons will be constructed to allow cross drainage at irrigation canals.



Appendix 1 – Hydrology

Hydrological setting

Catchment

There is considerable difficulty determining the effective catchment of Trapaing Thmor reservoir. Figure 10 shows the topographic catchment about 952 km2. The Trapeang Thma Irrigation Rehabilitation Project2 estimated the catchment of the reservoir to be 997 km2. A DTM†† also gives about the same area. But various independent studies indicate that the effective catchment is much less.

Figure 10 Trapaing Thmor reservoir catchment

†† Digital terrain model.



The main rivers catchments draining into the reservoir are the Prek Srae Memay and Prek Anlong Thom. These two rivers have a confluence about 5.0 km west of the reservoir and then flow into the reservoir via the Ou Chambak. These are the only two significant streams supplying the reservoir although higher ground to the north means it will capture overland flow originating up to 24 km back from the shoreline. Also a broad valley extending to the north east can convey flood flow spilled from the Stung Sreng river basin. Scour through bridge openings and culverts in a road embankment about 11 km north of the dam and a road between Pongro and Samraong are evidence that flood flows come from the Stung Sreng. Satellite images also indicate that the valley is flooded during the wet season right back to the Stung Sreng (Figure 11 and Figure 12 which follows).

In addition a new canal constructed under the Stung Sreng Water Resource Development Project will in future be able to transfer water from the Stung Sreng into Trapaing Thmor Reservoir. This will be a controlled inflow and should not significantly impact the flood hydrology although it will improve management of the limited water resource.

The feasibility study for the NWISP Punley subproject3 and subsequent detailed design studies which included continuous flow measurements for one wet season4 both found that the effective catchment was about 341 km2 smaller than the measured topographic catchment. In parallel the Trapeang Thma Irrigation Rehabilitation Project concluded the effective catchment of Trapaing Thmor reservoir was 530 km2 therefore much less than the same studies measured 997 km2. The explanation is the very gently sloping catchment without relief which in combination with road embankments and irrigation works is slowing and diverting runoff into neighbouring catchments, in particular the Svay Chek catchment. However, these studies were based upon data and observations for normal years, during extreme, widespread and prolonged floods, as have affected northwest Cambodia in 2009, 2011 and 2013; it is probable that whole topographic catchment will drain into Trapaing Thmor reservoir. This may have been a factor in 2011 and 2013 but even so it did not cause overtopping of Trapaing Thmor dam. The conclusion is that a although a smaller effective catchment can be assumed for water resource studies the catchment area of 997 km2 determined by the 2003 studies should be used for considerations of flood hydrology.

Flood Areas

A good indication of the usual extent of flooding at Trapaing Thmor and surrounding areas can be found from available remote sensing images. Figure 11 is a composite Landsat image, the dates are not known but it predates the reservoir rehabilitation in 2004. The blue areas are water and the pink areas are saturated soil. The ancient valley of the Prek Srae Memay and Prek Anlong Thom which used to drain into the Ou Preah Netr Preah can be traced from the flooding. The Ou Chambak is an obvious, albeit long established catchment transfer.



Figure 11 – Landsat image of flooded areas of Trapaing Thma and environs

Figure 12 is a radar image taken on 30 August 2000. This type of sensing detects changes in texture and the layers shown indicate flooding. The black areas are deep water and the red areas are flooded land. The stages of flooding in the two figures may be different but the images give a consistent picture of the flood extent.

It is rather difficult to get reliable information from farmers about the impact of inundation from the reservoir. There is a consensus that there is never a crop failure due to too little or too much water. Farmers us rice varieties and cropping schedule adapted to fit the hydrological regime of the reservoir. It can be concluded that fields bordering the reservoir were flooding before the reservoir was rehabilitated in 2004. It is also clear that the whole of the ancient river valley downstream to the Ou Preah Netr Preah also floods.

Rainfall There are available daily rainfall records from within the catchment and surrounding the catchment (Table 11).

Table 11 – Daily raingauge records for locations closest to Trapaing Thmor Reservoir and command area

Rain gauge Number of years Annual average

Code Station Year available

No mm

130205 Svay Chek 01-05 5 with gaps 855

130317 Thmar Pouk 01-06 5 with gap 678

130202 Sisophon 61-72, 87-96, 00-13 35 no gaps since 01 1248

130308 Phnom Srok 38-40, 61-64, 01-06 13 (3 with gaps) 1178

140401 Samroang 10-13 4 1360

130306 Siem Reap 88-11 23 1470

Stations 130309 Chong Kal and 130316 Preah Netr Preah excluded because only two years record is available.

Figure 12 – Radar image 30 August 2000



Immediately apparent are the much lower annual averages for Svay Chek and Thmar Pouk which are the two rain gauges within the Prek Srae Memay and Prek Anlong Thom and Trapaing Thmor catchments. This is the rain-shadow effect caused by the strong physiographic influences exerted by the Cardamom and Dangrek mountains. Areas around the Tonle Sap Lake suffer from persistent rain-shadow effects. During dry years, the area suffering from rain-shadow effects broadens from areas either side of the Tonle Sap Lake.

In contrast the 10 years full record for Phnom Srok is not so different from the long records for Sisophon and Siem Reap. It is appropriate to base inflows to the reservoir on the two records at Svay Chek and Thnma Pouk but to use the record for Phnom Srok for calculating crop water requirements (Figure 13 to Figure 15).

Figure 13 – Summary of monthly rainfall at Thma Pouk

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Figure 14 – Summary of monthly rainfall at Svay Chek

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Figure 15 – Summary of monthly rainfall at Phnom Srok

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Flood Discharge The unique location of Trapaing Thmor Reservoir and lack of any hydrological record mean that it is extremely difficult to prepare robust estimates of flood discharge or assign frequency. Land upstream and downstream of the reservoir is inundated annually but the flooding will vary in extent and duration depending on whether it is a dry or a wet year or whether there are weather effects such as a succession of tropical depressions moving through Cambodia which combine to cause an extreme event. However, the peak reservoir levels observed during the 2013 flood are sufficient to estimate peak discharge for this one event.

2013 Flood

The tilting gates initially failed to open automatically on the rising flood. Reservoir water level peaked 0.6 m below dam crest level which is 1.4 m above the closed gate and fixed weir crests levels. This means the reservoir water level reached 18.19 m elevation. At this time it is reported all eleven sluice gates were open, probably also some culvert head regulators. Under these conditions the total discharge from the three irrigation structures would have been about 242 m3/s. This is the reservoir outflow but taking into account reservoir routing (see below), the corresponding inflow hydrograph would have peaked about 495 m3/s plus an allowance for base flow. The reservoir routing depends on the stage-storage characteristics of the reservoir. Different characteristics to those assume would charge the estimated inflow. But the assumptions made provide a reasonable basis to extrapolate the design case from the observed 2013 flood.

Trapeang Thma Irrigation Rehabilitation Project Estimates

The 2003 Trapeang Thma Irrigation Rehabilitation Project assuming an effective catchment area of 530 km2 estimated the peak discharge of the mean annual flood (MAF) to be 283 m3/s, the 1 in 10 year flood to be 433 m3/s and the 1 in 100 year flood to be 622 m3/s. These flood estimates were made with a regression equation from the Halcrow Studies5 6 for catchments in



Thailand, commonly referred to in Cambodia as the IRS Method. The first cited reference does emphasise that the method is not suitable for use in detailed design without full consideration of all available local data. These estimates are considered unreliable because: (i) the full topographic catchment is probably draining to Trapaing Thmor reservoir during a major flood event; and (ii) the method is known to generally overestimate discharge (this is probably why a reduced catchment area was assumed). For comparison these estimates put the 2013 flood as about a 1 in 25 year event.

Modified IRS Method

The IRS Method uses a simple regression equation to estimate MAF. More recently the IRS Method has been refined based on regional flood frequency analysis for Cambodian catchments. This yields lower estimates for MAF from the following equation:

9.03981.0 AREAMAF

The growth factors for the 1 in 50 and 100 years floods are 2.0 and 2.2 respectively. Applied for Trapaing Thmor reservoir and a catchment area of 656 km2 the Modified IRS method yields more credible estimates of discharge. The peak discharge estimates are: MAF 199 m3/s, 1 in 50 year 398 m3/s, and 1 in 100 year 438 m3/s. These estimates put the return period of the 2013 flood greater than 1 in 100 years.

Climate Change

There is limited specific guidance for climate resilience for Cambodia which can be applied for engineering design. However the current NDF/ADB Climate Change Adaptation Project‡‡ has used hydrological modelling to predict the potential increase in flooding until the end of the century. This indicates that flood flows may on average increase by 10% to 20% and that corresponding flood depths might increase by 0.3 m to 0.5 m. These estimates must be treated with caution, in particular local infrastructure developments and changes in land use have potential for greater and more immediate changes in flood regimes than those projected for climate change. But nevertheless the figures do provide a quantifiable basis for considering climate adaptation.

For high risk infrastructure such as dams and spillways it is prudent to err on the side of caution. It is therefore proposed that design discharges are increased by 20% being the upper bound average increase predicted by the Climate Change Adaptation Project.

Design Discharge

Taking account of climate change the recommended peak design discharge is the estimated peak discharge of the 2013 flood plus 20%. This is 594 m3/s.

‡‡ Nordic Development Fund/Asian Development Bank Climate Change Adaptation Project, RRP.CAM 42334, Ministry of Rural Development.



Reservoir Stage-Storage Relationship. Before rehabilitation in 2004 the spill elevation and reservoir water level were 15.99 m§§ with useable storage about 63.4 MCM (million cubic metres). The rehabilitation raised the spill elevation to 16.79 m and increased useable storage to 141.5 MCM***. Figure 16 shows the reservoir stage-storage relationship derived from these two known points. The curve flattens when storage reaches 63.4 MCM because of the very gentle slope of the land. The volumes are based on reservoir area at different elevations.

Figure 16 Reservoir stage-storage relationship

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The 2003 Trapeang Thma Irrigation Rehabilitation Project stated that the maximum historic water level occurred in 1979 when it reached 16.64 m elevation, which is before the reservoir storage level was raised. The reservoir filled during the 2011 and 2013 floods. It is not clear that it fills every year; there is evidence to suggest it does not. Set against this are complaints from farmers around the reservoir that their fields were flooded after the spillways were raised. The evidence of water marks suggests water level peaks about 16.39 m or about 0.4 m higher than the pre-2004 high water level. So there is little doubt that the works have caused some flooding of fields. The 2003 studies mentioned a reservoir high water level of 17.29 m. This indicates the design freeboard was 1.5 m.

§§ Elevations are corrected referenced to the datum used for FDERP-AF design drawings, the original elevations stated in referenced documents may differ.

*** There is anecdotal information from PDWRAM the useable storage is 180 MCM and the PIU have quoted this on the design drawings. However this hydrological study has used the lower storage from the Trapeang Thma Irrigation Rehabilitation Project because the basis used by that project is known to be considered and explained.



Existing Spillway Capacity The reservoir spill level is the FSL which is 16.79 m elevation. There are three main outlets with a combination of gates and fixed crest weirs which can overtop at FSL.

At the head of MC1 Irrigation Structure 1 is 30 m wide with a pair of 13.5 m wide automatic counterbalanced tilting gates plus a 1.8 m wide sluice gate for releasing flow to the canal. When the tilting gates are closed the gate crests are at 16.79 m elevation, when fully open the crest level is 15.99 m elevation.

At the head of MC2 Irrigation Structure 2 is 30 m wide comprising 20 m wide fixed crest weir at 16.79 m elevation and five 1.8 m wide sluice gate for releasing flow to the canal. The top of the gates are about 16.79 m elevation so if they are closed water will weir over the top

At MC3 there is a 10 m wide structure. There are five 1.8 m wide sluice gates and no weir. But the top of the gates are about 16.79 m elevation so if they are closed water will weir over the top.

There are seven box culvert head regulators which can also be opened to release flow.

Figure 17 illustrates the stage discharge relationship for: all gates closed; all sluice gates open but tilting gates closed; tilting gates open but sluice gates closed; and all gates open. It is apparent that without reservoir routing (see below) there would be insufficient capacity to pass the peak discharge.

Figure 17 Stage-discharge relationship for Trapaing Thmor outlet structures

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Reservoir Routing The large area of the reservoir means that there is a significant flood routing effect†††. Basically the peak discharge leaving the reservoir over the spillways is significantly lower than the peak discharge entering the reservoir.

Figure 18 shows the routing of the 2013 flood through the reservoir before the tilting gates opened. The inflow hydrograph is back calculated from the outflow discharge of 242 m3/s based on observed reservoir levels. This indicates a peak inflow of 495 m3/s plus 22 m3/s allowance for base flow. As previously mentioned to freeboard at the dam was only 0.6 m during the peak discharge. In 2013 peak flows continued for about a week which is similar to that indicated by the flood routing model.

Figure 18 Flood routing of 2013 flood before tilting gates opened

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Figure 19 illustrates the reservoir routing for the recommended design peak inflow 594 m3/s plus an allowance of 22 m3/s for baseflow. A Unit Hydrograph has been used to generate the inflow hydrograph; the volume below the hydrograph is the total volume of the flood and in this case is the equivalent of a monthly rainfall of 450 mm. The time to peak has been assumed to be six days and the base time is 30 days. These parameters have been chosen to model prolong rainfall and inundation typical of northwest Cambodia and as has occurred recently in 2009, 2011 and 2013. The hydrograph is routed through the reservoir using the continuity equation for hydrology.

††† Reservoir Routing is used to determine the attenuation of the outflow hydrograph when a fraction of the inflow hydrograph enters temporary storage above the crest level of the reservoir spillway.



Put simply, the inflow to the reservoir is equal to the outflow of the reservoir plus the change of storage.

The peak outflow would be 290 m3/s. At this discharge the freeboard would only be 0.4 m. This is clear justification for the addition of a wave wall as proposed by the design. The wave wall should be not less than 19.8 m elevation, which is 1.0 m above dam crest level. A wave wall must be designed to be stable for hydrostatic and hydrodynamic forces.

Figure 19 Flood routing of the design flood through Trapaing Thmor Reservoir

Inflow/Outflow Hydrographs

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Discharges to main canals The most serious problem at Trapaing Thmor is that the irrigation canals do not have the capacity for the flood discharges released from the three main irrigation structures which function as spillways. The observed water levels during the 2013 flood and the reservoir routings clearly show this.

Table 12 shows the flows to the canals at two key times during the 2013 flood. Before the tilting gates were opened MC2 was receiving the highest flow 106 m3/s. This is because of the five open gates and the fixed crest weir.

But when the tilting gates were forcibly opened the total discharged will have immediately increased to 275 m3/s. This is because of the greater water head with respect to the reduced crest level at the tilting gates. There will have been a flood wave down main canal MC1 with flow suddenly increasing from 86 m3/s to 161 m3/s.



Table 12 Discharge to main canals during 2013 flood

Irrigation Structure 1 to

main canal MC1


main canal MC2


main canal MC2 Totals

m3/s m3/s m3/s m3/s

Tilting gates closed, sluice gates open

86 106 50 242

Tilting gates open 161 106 50 275

The situation will be worse under the design flood because of the larger flows as illustrated by Table 13. At these high discharges the flows are not that sensitive whether the gates are open or closed.

Table 13 Discharge to main canals during the design flood


main canal MC1


main canal MC2


main canal MC2 Totals

m3/s m3/s m3/s m3/s

All gates closed 126 125 42 293

All gates open 107 126 57 290

Increasing the spillway capacity would actually make the situation worse. This was tested by modelling replacement of the tilting gates by labyrinth weirs at Irrigation Structures 1 and 2. The net effect would be much higher flows to MC1 and MC2 and minimal improvement to freeboard at the dam.

In fact, the best use of the dam is to regulate flood releases downstream. This is achieved by mobilizing the live storage to attenuate the flow, exactly as is shown by the reservoir routing. The low freeboard can be corrected by provision of a wave wall.

But a large fraction of flow will still pass the spillway. Besides excavating the canals as large drains the only possible means to protect the canals is to manage the flow by allowing it to pass into bank storage. This means letting the flood spread to the rice fields. This is in fact what currently happens during every flood; flood water escapes the canals at the weakest places in the banks and causes significant damage. But the difference would be to spread and control the overspill to minimise crop damage and prevent scour and erosion. This can be achieved with long low sections of bank designed as reinforced grass spillways.

Water Resources There are currently no useable water resource observations for Trapaing Thmor reservoir. The best available records are for the Stung Sreng at Kralanh and these are of dubious quality. One problem in particular is that the effective catchment of the Stung Sreng is much less than the topographical catchment for the same reasons as the effective catchment of Trapaing Thmor is much less than its topographic catchment; principally that there are significant blockage, diversion and catchment transfers.



The data for the Stung Sreng was most recently published by the Water Resources Management Sector Development Program (WRMSDP), although it is the same as published earlier in the Tonle Sap Lowland Stabilization Project, Report on Water Availability7. This the WRMSDP study was a program component to address national water resources management and irrigation policy issues in Cambodia, and an investment component to assist MOWRAM to rehabilitate small- and medium-scale irrigation systems and deliver irrigation services within the Tonle Sap Basin. A detailed assessment of water resources data was completed by WRMSDP April 2014 and reported in the Cambodian Water Resources Profile8.

At Annex 4 of the Report there are tabulations of the monthly flow volume of every gauged river in Cambodia. Table 14 and Table 15 for flow entering Trapaing Thmor Reservoir are derived from the data for the Stung Sreng at Kralanh using the same formula as flood transposition. The effective catchment assumed is 656 km2. The limitations of the estimates in the table are acknowledged but they are nevertheless the best data based upon observation that is available for estimation of water availability from the Trapaing Thmor Reservoir.

Table 14 – Water availability (MCM) entering Trapaing Thmor Reservoir

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

1997 1.9 0.2 0.1 0.2 0.1 0.3 15.1 105.5 79.1 133.8 5.4 1.5 343.1

1998 0.1 0.1 0.1 0.1 0.1 0.1 4.6 20.7 25.6 77.9 27.6 2.5 159.3

1999 0.2 0.1 0.1 0.4 43.4 112.9 103.2 45.2 30.9 113.8 83.4 7.8 541.2

2000 0.8 0.1 0.1 1.4 10.6 78.3 204.5 148.1 138.6 137.1 64.9 5.3 820.1

2001 0.7 0.1 0.1 0.1 0.2 0.2 10.8 64.6 111.3 136.2 139.0 5.3 468.7

2002 0.5 0.1 0.1 0.1 0.2 2.4 21.7 17.1 145.0 128.9 43.7 10.3 370.1

2003 0.8 0.1 0.1 0.2 0.2 0.2 0.6 0.5 31.9 135.6 27.5 1.7 199.3

2004 0.1 0.1 0.1 0.1 0.1 22.0 9.4 141.4 133.5 61.0 4.2 1.8 373.8

2005 0.5 0.2 0.1 0.1 0.1 0.6 15.3 22.3 72.8 95.0 46.7 0.4 253.9

2006 0.1 0.1 0.1 0.1 0.1 0.3 7.9 145.0 142.9 189.0 79.2 4.9 569.8

2007 0.1 0.1 0.1 0.1 13.3 0.3 0.9 38.5 88.3 121.1 41.9 0.1 304.9

2008 0.1 0.1 0.1 0.1 0.3 0.6 14.6 54.9 148.1 173.2 160.5 30.6 583.1

2009 0.0 0.1 0.1 0.1 0.2 0.5 11.0 41.9 93.1 191.7 41.9 1.5 382.3

2010 0.7 0.6 0.7 0.6 0.7 2.9 4.1 146.2 175.1 226.9 85.9 0.4 645.3

Maximum 1.89 0.63 0.69 1.38 43.38 112.86 204.48 148.05 175.05 226.93 160.49 30.64 820.06

Average 0.48 0.15 0.15 0.27 4.97 15.81 30.27 70.85 101.16 137.24 60.84 5.29 429.64

Minimum 0.05 0.08 0.07 0.06 0.06 0.07 0.64 0.50 25.64 60.98 4.22 0.38 159.28

20% Exceedence 0.75 0.14 0.13 0.30 4.63 10.52 17.85 142.84 143.75 179.55 84.40 6.31 575.10

50% Exceedence 0.33 0.11 0.11 0.12 0.20 0.53 10.92 50.06 102.24 134.72 45.20 2.14 378.02

80% Exceedence 0.12 0.09 0.09 0.10 0.12 0.24 4.42 21.66 56.43 106.25 27.55 1.04 284.52

Source: Reference 8



Table 15 – Water availability (m3/s) entering Trapaing Thmor Reservoir

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

1997 0.71 0.06 0.04 0.06 0.05 0.12 5.64 39.38 29.53 49.96 2.02 0.55 10.88

1998 0.05 0.03 0.03 0.02 0.02 0.03 1.72 7.73 9.57 29.10 10.30 0.92 5.05

1999 0.07 0.04 0.03 0.16 16.20 42.14 38.51 16.88 11.55 42.48 31.15 2.91 17.16

2000 0.31 0.04 0.03 0.51 3.95 29.22 76.35 55.28 51.77 51.20 24.24 1.97 26.00

2001 0.28 0.05 0.05 0.05 0.08 0.06 4.03 24.13 41.57 50.86 51.88 1.98 14.86

2002 0.17 0.04 0.05 0.04 0.08 0.88 8.11 6.37 54.14 48.14 16.31 3.85 11.74

2003 0.28 0.03 0.05 0.07 0.07 0.08 0.24 0.19 11.89 50.63 10.27 0.62 6.32

2004 0.05 0.03 0.03 0.03 0.04 8.21 3.52 52.78 49.84 22.77 1.57 0.68 11.85

2005 0.17 0.06 0.04 0.03 0.03 0.23 5.70 8.33 27.19 35.45 17.44 0.14 8.05

2006 0.04 0.04 0.05 0.04 0.05 0.10 2.97 54.14 53.35 70.57 29.56 1.84 18.07

2007 0.05 0.04 0.05 0.04 4.96 0.10 0.35 14.39 32.96 45.20 15.63 0.06 9.67

2008 0.05 0.04 0.04 0.04 0.13 0.22 5.44 20.50 55.28 64.68 59.92 11.44 18.49

2009 0.02 0.04 0.05 0.05 0.07 0.17 4.12 15.63 34.77 71.59 15.63 0.57 12.12

2010 0.26 0.24 0.26 0.23 0.25 1.07 1.54 54.60 65.36 84.73 32.06 0.15 20.46

Maximum 0.71 0.24 0.26 0.51 16.20 42.14 76.35 55.28 65.36 84.73 59.92 11.44 26.00

Average 0.18 0.06 0.06 0.10 1.86 5.90 11.30 26.45 37.77 51.24 22.71 1.98 13.62

Minimum 0.02 0.03 0.03 0.02 0.02 0.03 0.24 0.19 9.57 22.77 1.57 0.14 5.05

20% Exceedence 0.28 0.05 0.05 0.11 1.73 3.93 6.66 53.33 53.67 67.03 31.51 2.35 18.24

50% Exceedence 0.12 0.04 0.04 0.05 0.07 0.20 4.08 18.69 38.17 50.30 16.88 0.80 11.99

80% Exceedence 0.05 0.03 0.03 0.04 0.04 0.09 1.65 8.09 21.07 39.67 10.29 0.39 9.02

Source: Reference 8



Appendix 2 – Sketches of Emergency Repairs

Typical cross-section for dam extension

Wave wall cross section

Typical cross-section of main canal

19.8 m elevation

Reservoir side





Appendix 3 – Stage 2 Assessment and Confirmation Sheet Subproject Name: Trapaing Thmor

Sector: Water - Irrigation Province: Banteay Meanchey

Location: Phnom Srok and Preah Netr Preah District, East-Northeast of Sisophon City (60 km)

Preliminary cost estimate: $2,500,081.70 Prepared by: PMU-ADB&BS/MOWRAM and PDOWRAMBM

Brief Description of subproject and the flood damaged incurred: Large storage dam – shallow with large surface area (as show on the map) – to supply 35,000 ha command area via existing and newly constructed earth channels, for predominantly 2 season rice crop. Damage – wave erosion of dam wall, flood flush of dam wall, erosion and washout of new canal banks, flooded through canals inundating villages and key public infrastructure (schools), back up of flood water against National Highway 6, with some overtopping (though only minor damage), flood control and passage of flood, dam wall under high water levels has demonstrated weak areas with observed seepage, requiring strengthening for future events. Overall flood management operations and capacity to moderate floods needs to be reviewed and improved.

Reasons the subproject needs completing before 2014 wet season (Stage 2 work): Canal banks need to be restored where washed out; infill around structures needs to be replaced; eroded face of dam requires upgraded protection to mitigate on-going wave action erosion; overall functionality for normal operations to be secured.

Brief description of proposed works: (include main works components damaged and repairs

proposed) 1. Earthworks of Main Canal MC-1, repair washout on the bank of Main Canal at the Station

Sta.0+320, Sta.0+502 and Sta.2+273, estimated cost 110,890.00 US$ 2. Earthworks of Main Canal MC-2, repair washout on the bank of Main Canal from the

Station Sta.0+000 to Sta.6+260, estimated cost 158,763.50 US$ 3. Earthworks of Main Canal MC-3, repair washout on the bank of Main Canal at the Station

Sta.3+530 and Sta.3+939, estimated cost 34,745.10 US$ 4. Earthworks of Drainage Canal DC-1, repair washout on the bank of Canal at the Station

Sta.2+588, Sta.3+631 and natural spillway at the station Sta.0+259, Sta.0+779, Sta.2+060, Sta.2+752, Sta.3+480, Sta.4+114 and Sta.4+967, estimated cost 81,626.30 US$

5. Earthworks of Drainage Canal DC-2, repair washout on the bank of Canal at the Station Sta.0+271, Sta.0+861, Sta.6+603 and natural spillway at the station Sta.0+430, Sta.2+103, Sta.3+910, Sta.4+961, Sta.6+309 and Sta.6+549, estimated cost 63,326.30 US$

6. Earthworks of Phnum Dei-Prey Moan Main Canal, repair washout on the bank of Main Canal from the Station Sta.000 to Sta.19+500 and natural spillway at the station Sta.13+696, Sta.15+396 and Sta.16+773, estimated cost 148,215.00US$

7. Additional check gates on the old check gates cross the main canal MC-1, MC-2 and MC-3, estimated cost 302,448.00 US$

8. Earthworks of Ang Trapaing Thmor Dam Slope Protection Ch8+000 to Ch11+000 and Ch14+000 to Ch16+500, estimated cost 499,979.50 US$

9. Gabion Box and Mattress Ch11+000 to Ch14+000 dam slope to be protected with rock filled mattresses – up to 3 km and 7 concretes stair, estimated cost 1,200,088.00 US$



Appendix 4 – Selection Criteria Screening

In addition to the General selection criteria, irrigation subprojects must satisfy the following requirements (Appendix 1, Item 4, of the PAM, March 2014).

(i) The subproject will have an already established Farmer Water User Communities (FWUC) made up of the beneficiaries. The FWUC must at least have agreed and adopted statutes and by-laws, registered its members and elected the FWUC Board of Directors and be well advanced towards being registered with the Department of FWUC. The FWUC should be active and working effectively and with a confirmed commitment to participate and contribute to preparation and implementation of the physical repairs.

Satisfies selection criteria. There is an existing FWUC registered with MOWRAM.

(ii) Proposed subprojects must have been impacted by flash flood (i.e. upland runoff and/or dam break) as a result of the 2013 wet season rainfall and climate impacts;

Satisfies selection criteria. Significant damage caused by 2013 floods from upland runoff, malfunctioning gates exacerbated the damage, vulnerability to climate change from flood and drought.

(iii) Auxiliary works (e.g. channel scour protection) may be included if they are required to ensure the effectiveness of other flood repairs and prevent possible degradation of the overall system

Satisfies selection criteria. Not an issue for Trapaing Thmor Irrigation System.

(iv) Works for repair of canals will be limited to main and secondary canals only. For the smaller canals, the Project will provide structures on the condition that the FWUC agrees to complete the minor earthwork repairs.

Satisfies selection criteria. Work on canals is confined to main canals.

(v) Any Stage 2 works proposed will involve no resettlement.

Criteria previously satisfied. There was no resettlement for Stage 2 works.

(vi) The proposed subproject shall be located in an area cleared of land-mines;

Satisfies selection criteria. Areas cleared of mines.

(vii) Where conditions have changed from when the original facility was constructed thereby requiring a major improvement, the proposed improvement will be regarded as Stage 3 work and will be subject to economic evaluation and prior approval of ADB. In this case, justification for inclusion must include a description of the effect and extent of damage caused by the 2013 flood.

Satisfies selection criteria. Conditions have not changed from when the original facility was constructed.



(viii) If the average repair costs of the scheme are US$1,000/ha or less over the gross area to be irrigated after the repairs are complete, then implementation may proceed without the need to verify economic viability;

Satisfies selection criteria. For a gross area 23,000 ha the cost is US$133/ha, for a gross area 20,000 ha the cost is US$153/ha, and for a gross area 6,020 ha the cost is US$508/ha.

(ix) Average repair costs of any one irrigation system should not exceed $2,000/ha across the gross area that will be in operation when the repair work is completed, and if it is more than $1,000/ha, will have a minimum EIRR of 12% based on detailed studies.

Criteria not applicable, cost is less than US$1000/ha.

(x) MOWRAM will develop effective and sustainable water and flood management strategies for all flash flood affected water storage and irrigation systems, and when additional hydromet data becomes available, integrate the new data in real time into updated flood management and flood response planning to mitigate flood risk across all sectors.

Criteria can be met by detailed design and O&M Plan. Hydromet station downstream at Prek Chik is being provided under FDERP-AF.

There is an addition criteria to be met, not included in the PAM, March 2014. This is included in the RRP, April 2014, III. Due Diligence, A. Economic and Financial, paragraph 23.

The economic internal rate of return for all stage 3 subprojects is expected to be greater than 12%.

Satisfies selection criteria: EIRR is 15.3%.



Appendix 5 – Involuntary Resettlement Impact Check-list

Screening for Resettlement Categorization. Date: 29 September – 03 October 2014

Involuntary Resettlement Effects Yes No Not

known Remarks

Information on Project areas and Involuntary Acquisition of Land

1. Does the sub-project include upgrading or rehabilitation of existing physical facilities?

2. Will easement be utilized within an existing Right of Way (ROW)?

Whereby ‘physical facilities’ are canal shoulders.

3. Will there be land acquisition?

4. Is there site for land acquisition? N/A

5. Is the ownership status and current usage of the land known?

6. Is the ownership status and current usage of land to be acquired known?

Government land; Right of Way

7. Will there be loss of shelter and residential land due to the land acquisition?

8. Will there be loss of agricultural plots and other productive assets due to the land acquisition?

9. Will there be loss of crops, trees, and fixed assets due to the land acquisition?

10. Are there any non-titled people who live or earn their livelihood at the site or within the COI / Right of Way?

11. Will there be loss of businesses or enterprises due to the land acquisition?

12. Will there be loss of income due to the land acquisition?

13. Will any social or economic activities be affected by land use-related changes?

Involuntary restriction on land use or on access to legally designated parks and protected areas

14. Will people loss access to natural resources, communal facilities and services?

15. If land use is changed, will it have an adverse impact on social and economic activities?

16. Will access to land and resources owned communally or by the state be restricted?

Information on Displaced Persons:

17. Any estimate of the likely number of persons that will be displaced by the project? If YES, approximately how many?

18. Are any of them poor, Female-headed of household, or vulnerable to poverty risks?

19. Are there any displaced persons from indigenous or ethnic minority groups?



Appendix 6 – ADB Resettlement Principles and Policy Frameworks

The following summarizes the key ADB policies relevant to the preparation of Resettlement Plan for the project. The resettlement categorization report has been prepared based on ABD’s Policy on Involuntary Resettlement. The main purposes of this policy are to:

1 avoid land acquisition and involuntary resettlement wherever feasible; and

2 minimize it where it is unavoidable and insure that AHs or AP receive assistance, so that they would be at least as well off as they would have been in the absence of the project.

In cases where subprojects involve voluntary donation and no other land acquisition and involuntary resettlement impacts, the subproject will be classified as Category C. However, the PIU will prepare a report to ADB (to be attached to the classification form) which will document that: (i) The subproject site is selected in full consultation with landowners and any non-titled

affected people; (ii) voluntary donations do not severely affect the living standards of affected people and the

amount of agricultural or other productive land to be acquired from each affected household does not exceed 5% of the total productive landholdings of the household;

(iii) Voluntary donations are linked directly to benefits for the affected household; (iv) Any voluntary donation will be confirmed through written record and verified by an

independent third party such as the external monitoring organization; (v) There is an adequate grievance process; (vi) No affected household will be displaced from housing and severely affected; and (vii) No affected household is vulnerable.



Appendix 7 – Screening for Environmental Impacts

Rapid Environmental Assessment Checklist

Screening Questions Yes No Remarks

A. PROJECT SITING

Is the project area adjacent to or within any of the following environmentally sensitive areas?

Protected area

Wetland

Mangrove

Estuarine

Buffer zone of protected area

Special area for protecting biodiversity

The Reservoir is gazetted as the Ang Trapaing Thmor Crane Sanctuary, IUCN (International Union for Conservation of Nature) Category III (natural monument or feature) (see Chapter 4 -Chapter 4 -3.3.1). The sanctuary was gazetted on 1 January 1999 and covers an area of 10,250 ha. The site covers the open water area of the reservoir and the marginal wetland and grassland to the west and north of the open water.

B. POTENTIAL ENVIRONMENTAL IMPACTS

Will the project cause…

loss of precious ecological values (e.g. result of encroachment into forests/swamplands or historical/cultural buildings/areas, disruption of hydrology of natural waterways, regional flooding, and drainage hazards)?

As the subproject is to deepen and widen the existing canal and add some structures, no precious ecological values will be lost due to such rehabilitation.

conflicts in water supply rights and related social conflicts?

There is a pre-existing conflict (since 2004) between farmers upstream of the reservoir who suffer flood damage to crops at FSL and farmers downstream who require water storage for dry season irrigation. Currently the community manages the situation by releasing water from the reservoir when upstream farmers complain. The project will not remove the conflict but improvements to the gates and a clear O&M plan will mitigate the problem.

impediments to movements of people and animals?

No impediments to movements of people and animals will occur from the subproject rehabilitation.

potential ecological problems due to increased soil erosion and siltation, leading to decreased stream capacity?

The subproject will not provide any potential ecological problems due to increased soil erosion and siltation and will also be away from the stream.




Insufficient drainage leading to salinity intrusion?

There is an existing problem with salinity in areas of the subproject. This has been caused by seepage from canals, over irrigation and poor drainage. The subproject will mitigate the problem by improvements to canal and drains and providing an O&M Plan for better water level management.

over pumping of groundwater, leading to salinisation and ground subsidence?

No groundwater will be used and ground subsidence is not expected.

impairment of downstream water quality and therefore, impairment of downstream beneficial uses of water?

Impairment of downstream water quality is not expected.

dislocation or involuntary resettlement of people?

No involuntary resettlement of people is expected from the subproject site

disproportionate impacts on the poor, women and children, Indigenous Peoples or other vulnerable groups?

The subproject will not have any impact on the poor, women and children, indigenous peoples and other vulnerable groups

potential social conflicts arising from land tenure and land use issues?

The nature of subproject is just to improve the existing irrigation infrastructures. Therefore, social conflicts due to land tenure and land use are not expected

soil erosion before compaction and lining of canals?

No soil erosion before compaction and lining of canal is expected.

noise from construction equipment?

dust during construction?

Dust/suspended particles and noise will be generated from construction activities. They will be more salient during the construction period. These impacts will be temporary but, if not mitigated, will have potentials to result in long-term consequences in the health of the affected communities and the construction workers.

water logging and soil salinisation due to inadequate drainage and farm management?

Water logging and soil salinisation due to inadequate drainage and farm management are not expected from the subproject.

leaching of soil nutrients and changes in soil characteristics due to excessive application of irrigation water?

No leaching of soil nutrients and changes in soil characteristics due to excessive application of irrigation water is expected to be different from pre-subproject conditions.

reduction of downstream water supply during peak seasons?

Reduction of downstream water supply in particular during peak season will not occur due to this subproject rehabilitation.

soil pollution, polluted farm runoff and groundwater, and public health risks due to excessive application of fertilizers and pesticides?

Soil pollution will be likely to occur due to excessive application of fertilizers. This would not a major issue leading to public health risks.




soil erosion (furrow, surface)? No soil erosion is expected compared to pre-subproject conditions.

scouring of canals? No scouring of canal is expected.

clogging of canals by sediments? Clogging of canals by sediments is not expected either a short term period or a long term period.

clogging of canals by weeds? Clogging of canals by weeds is not expected for a short term period. However, this will probably occur for a long term (five more years) period if there is no proper maintenance.

seawater intrusion into downstream freshwater systems?

The subproject rehabilitation will not be adjacent to seawater. Therefore, seawater intrusion into downstream freshwater systems will not occur.

introduction of increase in incidence of waterborne or water related diseases?

The subproject rehabilitation will not cause increase in incidence of waterborne diseases.

dangers to a safe and healthy working environment due to physical, chemical and biological hazards during project construction and operation?

Dangers may occur but can be avoidable during construction by strictly implementing safety plan from the contractor e.g., fence active work sites and strictly disallow unauthorized entries, post watchman to secure sites and ensure no loitering near the site.

large population influx during project construction and operation that causes increased burden on social infrastructure and services (such as water supply and sanitation systems)?

There might have minor population influx not during subproject construction but operation period. However, this may not put a burden on social infrastructure and services.

social conflicts if workers from other regions or countries are hired?

Priority in labour employment will be provided to local residents while outsiders will be considered in case of lack in labour.

risks to community health and safety due to the transport, storage, and use and/or disposal of materials such as explosives, fuel and other chemicals during construction and operation?

No transport, storage, and use and/or disposal of hazardous materials such as explosives, and other chemicals during construction and operation are expected.

community safety risks due to both accidental and natural hazards, especially where the structural elements or components of the project (e.g., irrigation dams) are accessible to members of the affected community or where their failure could result in injury to the community throughout project construction, operation and decommissioning?

Working conditions at construction site will be secured. Only workers and subproject staff will be allowed to enter the construction and operation sites.




C. CLIMATE CHANGE AND DISASTER RISK

The following questions are not for environmental categorization. They are included in this checklist to help identify potential climate and disaster risks.

Is the Project area subject to hazards such as earthquakes, floods, landslides, tropical cyclone winds, storm surges, tsunami or volcanic eruptions and climate changes?

Flood and drought are the main natural hazards of Cambodia. These hazards will not occur from the subproject rehabilitation. However the subproject will improve the beneficiaries’ resilience to climate change.

Could changes in temperature, precipitation, or extreme events patterns over the Project lifespan affect technical or financial sustainability (e.g., increased glacial melt affect delivery volumes of irrigated water; sea level rise increases salinity gradient such that source water cannot be used for some or all of the year)?

The project is designed to improve resilience to more extreme and frequent flood and drought and maintain agricultural production.

Are there any demographic or socio-economic aspects of the Project area that are already vulnerable (e.g., high incidence of marginalized populations, rural-urban migrants, illegal settlements, ethnic minorities, women or children)?

Could the Project potentially increase the climate or disaster vulnerability of the surrounding area (e.g., by diverting water in rivers that further increases salinity upstream, or encouraging settlement in earthquake zones)?

Note: Hazards are potentially damaging physical events.



Appendix 8 – Environmental Management Plan (EMP)

Institutional Responsibilities Project Phase Project Activity

Potential Environmental

Impacts Proposed Mitigation Measures

Implement Supervise

Supervision Consultant, IA/EA


1. Damage to existing structures The design should maximize benefits or avoid impacts on assets. Resettlement framework for the subproject based on Cambodian laws, policies, and regulations should be applied.



Pre-construction Detailed design 2. Risk of land mine or UXO Consultative meetings with local

authorities and communities are necessary to know where there are risks of mines or UXO. Also, unsafe areas should be cleared before project implementation.



Construction

Earthworks, site clearing, hauling of construction material

3. Dust generation The contractor shall prepare and strictly implement dust control measures such as periodical water spray.

The contractor shall maintain their construction equipments in adequate working conditions.

The contractor shall keep clean road surfaces.

The driver of construction vehicles should comply with speed limits to minimize road dust.

The contractor and supervision consultant shall provide prior notification to the local community on schedule of construction activities.

The contractor shall prepare and strictly implement a traffic management plan around construction site.

The supervision consultant shall monitor dust, exhaust gas and complaint from the

Contractor and Supervision Consultant







Implement Supervise

local people.

If the local residents and pedestrians complain about the dust and gas, the supervision consultant and contractor should reconsider the construction technique and method.

4. Noise and vibration A proper work schedules should be prepared not to concentrate the construction equipment at a certain point for long time.

Construction works with heavy noise and vibration shall be prohibited during night (10:00 pm - 6:00 am) to avoid noise disturbance in residential, commercial and other noise-sensitive areas.

The contractor selects quiet equipment and working methods as much as possible.

The contractor and supervision consultant shall provide prior notification to the local community on schedule of construction activities.

The supervision consultant shall monitor noise, vibration and complaint from the local people in construction site, borrow pit and quarry site.

If the local residents and pedestrians complain about the noise and vibration, the supervision consultant and contractor should reconsider the construction technique and method.



5. Water pollution Construction works should be far away from streams, reservoirs or channels and concentrated in the dry period. Contractor Supervision Consultant,

IA/EA






Implement Supervise

The contractor shall strictly control waste oil and other waste.

The contractor will be prohibited from washing the construction tools along the rivers, streams, reservoirs and other public water to prevent further pollution.

The wastewater septic tank facility in the workers camp and/or other necessary locations shall be properly maintained.

The contractor shall prepare and strictly implement an environmental management plan on borrow pit or quarry site.

In case of purchase from quarry firm, the environmental management shall be included in the contract.

6. Soil pollution Diesel and waste oil shall be handled and stored carefully to prevent leakage or spill. Waste oil shall be collected, stored in drums and disposed at a site approved by the local authority and raised off the ground, covered to keep rain out and surrounded by a bund to contain any spills and simplify clean up.

Contractor Supervision Consultant,

IA/EA

7. Waste The contractor shall prepare and strictly implement a proper waste management plan.

The waste management plan should be approved by the local authority in advance of construction works.

The contractor shall provide temporary sanitation facilities such as portable toilets and garbage bins to ensure that the domestic wastes to be generated by the








Implement Supervise

construction personals.

Office building for the contractor shall be provided with toilets and septic tanks to handle domestic sewage.

The contractor shall consider and implement proper re-use plans of the construction waste.

The supervision consultant shall monitor the waste disposal.

The local authority should maintain closely consultation with the contractor on the collection of garbage.

8. Accidents of construction workers and local residents

The contractor shall comply with the implementation plan and also shall secure the working conditions.


IA/EA

9. Accident, social conflicts Provide warning sign board on the necessary irrigation infrastructures such as water gate, spillway and so on.


IA/EA Operation

Use of hydraulic facilities

10. Social conflicts, facilities and water use conflict

Establish FWUG and/or FWUC FWUG/FWUC Consultant

IA/EA

Note: IA = Implementing Agency; EA = Executing Agency; FWUG/FWUC = Farmer Water Users Group/ Farmer Water Users Community



References

1 ADB. Safeguard Policy Statement, Policy Paper, Asian Development Bank, Manila, June 2009.

2 MOWRAM. Project Proposal on Trapeang Thma Irrigation Rehabilitation Project, MOWRAM, January 2003.

3 Pacific Consultants International in association with SAWAC. Phase II Feasibility Report, Annex D Punley Subproject, Northwest Irrigation Sector Project (TA No. 3758-CAM), MOWRAM, October 2002.

4 Aruna Technology Ltd. Hydrology Report, Punley Sub-project, Aruna Technology Ltd, Phnom Penh, R1 January 2008.

5 Sir William Halcrow & Partners Ltd. Annex A Hydrology, Irrigation Rehabilitation Study in Cambodia, Final Report, Sir Wiiliam Halcrow & Partners Ltd in association with Mandala Agricultural Development Corporation, 1994

6 Farquharson F, Green C, Meigh J and Sutcliffe J. Regional Flood Frequency Analysis, Ed V P Singh, D Reidel, 1986.

7 Fraser Thomas with SDC. Report on Water Availability, Tonle Sap Lowland Stabilization Project, TA No. 4756-CAM, ADB, Manila, September 2006.

8 Egis Eau. Cambodian Water Resources Profile, Water Resources Management Sector Development Program, ADB Loan 2673-CAM and TA 7610-CAM, Phnom Penh, April 2014.

Documents

Flood Damage Emergency Reconstruction Project ...gdb.mef.gov.kh/fderp-af/contents/uploads/2014/08/...Egis Eau Document quality information Flood Damage Emergency Reconstruction Project