Ground Water Artificial Recharge in Spate Areas

(case study Wadi Ahwar in Yemen,)

Dr. Abdulla Noaman

Dr. Sharafaddin A. Saleh

INTRODUCTION

This report responds to the TOR and the data collection and analyses the results of which

were used in creating certain thematic groundwater maps reflecting the groundwater

conditions in the Ahwar Delta. The report also presents data collection activities and

details of the required monitoring system.

Figure 1. Location Image of Delta Ahwar in Yemen

The study area has been witnessing groundwater irrigation development besides spate

irrigation with flood water. Agricultural development in Ahwar has started within the

framework of the GOY sustainable agricultural development perspective Year of

Agriculture (1984) which situates irrigation based agriculture at the heart of agricultural

development strategy in Yemen. After the year 1990, Agricultural development in Delta

Ahwar was has been escalated since the construction in 1990 of the Fuad and Hanad weirs

as well as through the increase of agricultural productivity through the expansion of

groundwater irrigated agriculture. To that effect extensive shallow tube wells (STWs) were

drilled and equipped in Delta Ahwar area.

Study Area

Delta Ahwar is located about 200km east of Aden. Ahwar, Al Hanad and Al Mabrak along

the coast of the Arabian Sea are major villages in the delta; the study area is also

considered as the flood plain delta of wadi Ahwar

Figure 2. Image showing Wadi Ahwar main drainage system and delta on the Arabian Sea

Ahwar Delta and main villages showing high resolution Images dates

4.0 CONJUNCTIVE USE OF SURFACE AND GROUNDWATER

In the Ahwar Delta, rain, and consequently peak runoff, which contributes to a significant

part of the total discharge of the wadis, occur during a particular season of the year. This

however, usually responds to smallest water demand. The water development problem

therefore is how to transfer water from the high supply season to the high demand season.

The most obvious and the most common solution would be storing surface water behind

dams. However, despite the fact that underground storage of water may be a valuable

alternative to surface storage systems, it is not always systematically considered when

planning water resources development. Surface reservoirs have many drawbacks, such as

loss of water by evaporation, sedimentation, the negative healthy impact on the human

environment and the high cost of water conveyance associated with surface water storage.

Conjunctive use of surface and groundwater consists of harmoniously combining the use of

both sources of water in order to minimize the undesirable physical, environmental and

economical effects of each solution and to optimize the water demand/supply balance.

Usually conjunctive use of surface and groundwater is considered within a wadi and delta

basin management program, in the same basin.

Assuming that the mixed solution is part of the national policy, several issues need to be

carefully studied before selecting the different options and elaborating a program of

conjunctive use of surface and groundwater:

• Underground storage availability to be determined,

• Production capacity of the aquifer(s) in term of potential discharge,

• Natural recharge of the aquifer(s)

• induced natural recharge of the aquifer(s)

• Potential for artificial recharge of the aquifer(s)

• Comparative economic and environmental benefits derived from the various possible

options.

5.0 UNDERGROUND STORAGE AVAILABILITY AND PRODUCTION

CAPACITY OF THE AQUIFER

In order to use the underground reservoir to store a significant volume of water, and use it

at a later stage, it is necessary to ascertain the potential storage capacity of the groundwater

reservoir as well as its suitability for being recharged by surface water and the water

recovery efficiency The groundwater reservoir should present sufficient free space between

the ground surface and the water table to accommodate and retain the water to be

recharged, for the period during which water is not needed. This condition requires

accurate hydro geological investigations including geological mapping, geophysics and

reconnaissance drilling, in order to determine the configuration and the storage capacity of

the underground reservoir.

The suitability of an aquifer for recharging may be estimated from the following

parameters:

• Surface material has to be highly permeable so as to allow water to percolate easily;

• The unsaturated zone should present a high vertical permeability, and vertical flow of

water should not be restrained by less permeable clayey layers;

• Depth to water level should not be less than 5 to 15 m, generally; the depth to water

table is rather deep in most of the delta for the application of this technique

• Aquifer transmissivity should be high enough to allow water to move rapidly from the

mound created under the recharge basin but should not be too high (as in karstic

channels) so that water cannot be recovered.

An adequate transmissivity of the aquifer material is also a good indicator of the aquifer

capacity to produce high well discharge and therefore easily to return the water stored.

6.0 NATURAL AND INDUCED RECHARGE OF THE AQUIFER

Natural recharge of the aquifer occur from the surface runoff and the deep percolation of

flood flows, as well as infiltration from adjacent water bodies, whether natural or artificial

such as reservoirs, lakes, and to a modest extent from irrigation water return, especially in

the case of shallow aquifers. To that effect should the average annual amount of recharge

be of the same order of magnitude as the water demand, there would not be the need for

any additional human intervention through the process of artificial recharge through the

modification of the natural course of surface water or the diversion of any surplus water

from an adjacent source.

Induced natural recharge occurs when intensive exploitation of groundwater close to a

river results in an important depression of the groundwater level and in a water inflow

from the river. This phenomenon is well known in temperate climate where rivers flow all

year long; but it may also occur in semi-arid climates where a depression of the

piezometric level of an aquifer underlying a temporary wadi deposits creates the empty

space in the aquifer which facilitates its recharge during floods.

6.1 Artificial Recharge

Artificial recharge of aquifers can be achieved using three different methods, namely

surface spreading, watershed management (water harvesting) subsurface dams and

recharge wells.

Surface spreading

Artificial recharge by the spreading method consists of increasing the surface area of

infiltration by releasing water from the source to the surface of a basin, pond, pit or

channel. This is certainly the most efficient and most cost-effective method for aquifer

recharge. However, only free (unconfined) aquifers can be recharged by the spreading

method, which also requires large surface areas to accommodate the recharge scheme,

allowing water to evaporate if percolation in the ground is slow.

Surface spreading usually needs two structures: the diversion structure and the infiltration

scheme.

Diversion structures are the same as those used for spate irrigation. The traditional

methods, based on centuries of experience, are well adapted to the conditions of arid land

wadis. They consist of the construction of earthen bunds (ogmas) and deflectors across the

wadi to divert the flow into the fields. But large spates usually destroy the ogmas and

reduce irrigation of the fields. Furthermore, the very high sediment content of spate water

tends to fill the diversion canals, which have to be cleaned regularly. So, although the

ogmas are relatively inexpensive to rebuild, the overall cost of seasonal maintenance and

repair of the scheme is high.

Several techniques have been tested with the objective of achieving a better control and

regulation of spate and reducing sediment transport in the canals. Due to the hydrological

characteristics of wadis, it soon became evident that it is not economic to provide diversion

weirs which will control the probable maximum flood. Thus, the tendency nowadays is to

build diversion structures with a canal head regulator, sediment excluder and a spillway on

one flank and a fusible dyke across the wadi. Unfortunately, present design and feasibility

studies are often hampered by lack of adequate data on spate runoff. These techniques

were developed with the intention of improving the spate irrigation systems, but the results

can apply to the diversion structures needed for artificial recharge by surface spreading.

The infiltration scheme may consist of basins, channels or pits depending on the local

topography and on land use. The most common system consists of a number of basins

each one having an area ranging from 0.1 to 10 ha according to space availability. Each

basin must have its own water supply and drainage so that each basin can be flooded, dried

and cleaned according to its best schedule. Basins should never be in series, because in

such a system, they cannot be dried and cleaned individually. Often the first basins are

used as pre-sedimentation facilities.

In the vicinity of urban areas, pits may have been dug in ancient paths of wadis in order to

extract construction material (gravel, sand). The depth of these pits may range from 2 to 3

m up to 30 to 40 m. Pits may also be excavated for the specific purpose of artificial

recharge. Aquifer recharge simply consists of diverting water from the main channel to the

pit. Even with a deep pit, it may be advisable to have a smaller settling pit between the

main channel and the larger recharge pit. Both recharge and settling pits should be fenced

and have a suitable inlet so that the inflowing water does not erode the walls of the pits.

Other techniques may also be identified with the surface spreading method: spate

irrigation, check dams, underground dams and sand dams.

Spate irrigation is a well known traditional technique in the area consisting of watering

terraced fields which flank the wadi, by diverting flood flows into them. Although the

primary objective of spate irrigation is not aquifer recharge, this technique usually

contributes significantly to increasing the infiltration of water into the underlying

groundwater reservoirs. The storage of excess water into the aquifer and its subsequent

retrieval alleviates some of the risks inherent to runoff based irrigation in arid zones.

Check dams are small structures built across wadis with a view to slowing down the

velocity of water, allowing it to percolate into the alluvial aquifer. When the wadi usually

flows into a narrow channel surrounded by plains located a few meters above the bottom of

the channel, check dams may be built in the channel, raised 1 to 2 meters above the ground

level of the plain and extended laterally by two wings crossing most of the stream bed. The

flood is then forced to pass through artificial meanders over a long path and large area and

to slow the flood velocities to enable the surface water to percolate and thus facilitating the

infiltration of water. However due to high silt load in runoff/flood water, check dams will

be subject to silt deposit and requires frequent desilting works.

Underground dams apply in shallow depth alluvial deposits to prevent groundwater

(underflow of the wadi) from flowing away immediately after it is stored in the aquifer.

They consist of digging a 1 to 1.5 m wide trench across the valley, down to the bedrock

and/or clayey impervious layer and then filling the trench either with loose impervious

material (clay) or by building a wall made of local bricks. Underground dams may be

complemented by sand dams consisting of raising the dam above ground by 1 or 2 meters

so that the solid transport (usually sand and gravel) of the floods can accumulate behind

the surface dam and thus increase the storage capacity of the alluvium. This technique may

not be suitable for a recharge system to the Ahwar area due to the depth of water which is

more than 40 meters in most of Ahwar Delta, detailed Hydrogeological and geophysical

sounding surveys should be conducted to determining the possible suitability of an

underground dam.

6.2 Watershed management and water harvesting

Watershed management offers an effective method to intercept dispersed runoff. Many

techniques of water conservation have been developed along hill slopes with the intention

of preventing soil erosion and reducing surface runoff, then increasing the infiltration in

the ground, thus recharging the aquifers. Traditional terraced agriculture is certainly one of

the most common water harvesting methods in arid areas and particularly in Ahwar upper

catchments. Where the terraces are well maintained, they effectively control runoff and

improve aquifer recharge but, once allowed to fall into disuse, they progressively lead to

gully erosion, collapse of the retaining walls, destruction of the whole system and severe

modification of the hydrological regime. Therefore, whatever the economic virtues of such

terraces, it should be recognized that their abandonment on a large scale can upset the

hydrological conditions within a basin for a considerable period of time.

Because of the siltation problems in the surface reservoirs resulting from soil erosion in the

upper catchment, large program of soil and water conservation as well as forestation

should be taken in several places of the Ahwar Catchment. Although the primary objective

of the watershed management is to limit the soil erosion and therefore to reduce sediment

accumulation in the surface reservoirs downstream, the effect of these practices may

become significant on the aquifer recharge when large areas are included in the programs.

Ahwar groundwater monitoring data both water level and water quality, should be stored

within a Groundwater Database system. The system should be based on web technology

and is available through.

Allocation and use data is obtained through the Database which is an electronic database

for water license details. Both databases are managed locally at district level, with respect

to the collection and entering of water monitoring, allocation and use data.

7.0 GROUNDWATER MANAGEMENT:

Management of the groundwater resource of the Ahwar Delta should aim at maintaining a

long term sustainable resource. Coastal aquifers prone to salt water intrusion, such as those

of the Ahwar Delta, remain capable of yielding a sustainable source of freshwater if

protective and flexible management practices are implemented. Protective management

requirements for the Ahwar Delta should include:

Construction and maintenance of the proposed subsurface dams of artificial

recharge scheme, with respect to replenishment encouragement and the

development of recharge pits, to ensure the long term sustainability of irrigation

based farming operations in the Delta;

Development of a groundwater management model for the Ahwar basin to assist in

evaluating the long-term water management strategies, consideration of the long

term protection of the groundwater system from saltwater intrusion, with

maintenance and continuation of water level and water quality monitoring.

Saltwater intrusion of the groundwater resources of Ahwar Delta could be a serious

problem in the coming few years, particularly after an extended drought period, which may

result in extreme reductions in groundwater levels below sea level due to excessive use.

Excessive demand placed upon the groundwater resources within the Delta has resulted in

water level declines and degradation of water quality in some areas of the Delta. The water

overdraft situation will finally be recognized after a severe drought, the implementation of

an artificial groundwater recharge scheme. Management of the water resources within the

Delta will significantly protect the aquifer, since the implementation of present irrigation

scheme, with the proposed underground system could be considered as one of conjunctive

use of both surface and groundwater.

Developing hydrological Monitoring system

Water-levels in piezometers, soil temperature, and several climatic parameters should

monitor automatically in the Ahwar Delta.

A monitoring network concept consisting of a number of groundwater monitoring wells

and a surface water station was conceived and evaluated to assess its overall effectiveness

at achieving the specific monitoring objectives, and to (1) identify potential opportunities

to streamline monitoring activities while still maintaining an effective monitoring program,

and (2) identify data gaps that may require the addition of additional monitoring points.

It should be indicated here that there are a variety of ground-water resource problems that

involve the Delta groundwater and affect detecting or predicting changes in the ground-

water environment... Any design for a monitoring system must combine techniques that

integrate stochastic ground-water flow and salinity transport /intrusion with optimization

for controlling and managing groundwater – surface water

Groundwater Levels fluctuations

Groundwater levels drop to more than 80 meters below ground surface in some parts of the

study area. However, several cones of depression occur in various parts of the study area,

whereby no accurate well elevations are available. To that effect, the Consultant prepared,

a tentative water table elevations contour map based on elevation readings measured by

hand held GPS. The contour elevation forms a close circle around the pumping wells in

farms. Despite the fact that this SWLE contour map is not reliable due to the lack of

accurate topographical survey, yet, it was observed that pH variation is directly related to

the depth to water level and water level depletion cones. Figure 5 represents a pH contours

map reflecting the actual depleted cone in the area, where one can observe that the main

groundwater flow direction is from North to South, but the flow direction has been

disturbed to receive water from all sides around the depleted cones.

Figure 5. PH Contour Map

Depth to water

Depth to water in the study area ranges from 10 below the surface along the sea coast in

the south to a maximum estimated at more than 80 meters below ground surface for some

parts of the depleted aquifer, Figure 6. In the Northern part of the delta area depth to water

is greater than 60 meters and is limited to some depleted cones as shown in the map below.

Reliable information describing the configuration of the water table in the Delta is needed

to help resolve a variety of water-resource issues including evaluation of aquifer

susceptibility to contamination, effects from storm water, evaluation of injection systems

for groundwater recharge, well drilling, and monitoring. Such a map would also serve as a

baseline to identify changes in water levels resulting from natural or human-induced

causes.

:.

Figure 6. Delta Ahwar depth of water table contour map

Abstraction

Estimation of annual abstraction of ground water by pumping were calculated at 24Mm3/yr

by applying the following two methods:

Total well discharge:

Based on the results of the well inventory, the total discharge of the wells in the delta was

estimated at 3143 l/sec., while the estimated total volume of abstracted water was 24 Mm,3

assuming that the number of pumping hours is 12 hr/day and number of operating days is

180 days.

Irrigated areas and farms count:

The groundwater irrigated area is estimated at 1930 herewith a total irrigation requirements

of estimated at 23.16 Mm3 (assuming the irrigation water requirement by ha is 12 000 m3

for a cropping intensity of around 150%). This is almost the same volume estimated by the

first method.

Groundwater modeling scheme for the target zone

Increasing and often competing demands between agricultural and municipal sectors on

the ground-water resources are creating a need for improved scientific information and

analysis techniques to better understand and manage ground-water systems. Numerical

simulation models became important tools for the assessment of ground-water flow

systems and ground-water development strategies. Commonly, these models are used to

test specific water-resource management plans, or, in a trial and-error approach, to select a

single plan from a few alternative plans that best meets management goals and constraints.

The main objective of ground-water flow models is to provide a quantitative and

qualitative assessment of ground-water resources in the water supply well field... The

model is a valuable tool for (1) estimating ground-water recharge, discharge, and storage at

spatial scales; (2) assessing the cumulative effects of existing and proposed water resource

uses and developments; and (3) evaluating the cumulative effects on water resource of

various water management options. Because of the complex nature of ground-water

systems, however, and the large number of engineering, legal, and economic factors that

often affect ground-water development and management, the process of selecting a best

operating procedure or policy can be extremely difficult. To address this difficulty, ground-

water simulation models have been linked with optimization-modeling techniques to

determine best (or optimal) management strategies from among many possible strategies.

Optimization models explicitly account for water-resource management objectives and

constraints, and have been referred to as management models. The use of combined

simulation-optimization models greatly enhances the utility of simulation models alone by

directly incorporating management goals and constraints into the modeling process. In the

simulation-optimization approach the modeler specifies the desired attributes of the

hydrologic and water-resource management systems (such as maximum allowable ground-

water level declines and safe yields ) and the model determines, from a set of several

possible strategies, a single management strategy that best meets the desired attributes. In

some cases, however, the model may determine that none of the possible strategies are able

to meet the specific set of management goals and constraints. Such outcomes, while often

not desirable, can be useful for identifying the hydrologic, hydro geologic, and

management variables that limit water-resource development and management options.

Because of their usefulness for evaluating complex hydro geologic and water-resource

management systems, simulation-optimization models have been developed to assess

various types of local ground-water management problems, such as

Ground-water-level declines and aquifer-storage depletions

Conjunctive use of ground-water resources

Ground-water contamination

Simulation optimization models should be applied to the important ground-water

productive aquifers as High-yielding sandstone and alluvial aquifers which are important

source of water in Ahwar area. Processing ModFlow of United States Geological Survey

could be as a useful tool to simulate the conditions of groundwater /water quality in the

study area. The groundwater flow models should be constructed for the detailed study for

this project and be calibrated in steady state conditions by matching the static water table

with the modeled water level. The model should be calibrated in transient flow by

matching the measured draw down (due to abstraction from the well fields) with the

modeled draw down.

A groundwater model should be applied to investigate the groundwater level fluctuations

and fresh-seawater relations in an unconfined coastal aquifer which could be form as a

result of land reclamation. The aquifer could be subject to appropriate open boundaries.

Groundwater level fluctuations at the site should be measured at least on weekly basis at a

number of observation standpipes. Hydraulic conductivity values for the site should be

estimated from a tidal influence constant hydrogeological parameters should be applied

throughout the aquifer.

The results obtained could verify whether the aquifer is homogenous or non homogenous.

The simulated head values should generally fit with the observed groundwater levels. The

simulated and observed groundwater flows radiate to the groundwater decline at the centre

of aquifer from the shorelines where the saturated thickness is the smallest. The model

should also able to estimate the increase in aquifer salinity due to abstraction.

Vertical salinity anomalies should be clarify the salinity stratification status and salt water

intrusion, high salinity water at the bottom water column and low salinity at the surface.

And to simulate the groundwater major vertical density differences related to distribution

of water temperature vertical variation. The groundwater scenarios and other simulation

works for AHWAR area should be seated in cooperation with modular and other study

team members at the detail design stage to serve the general model scheme for the targeted

zone is detailed in the Model Scheme ( Annex I)

8.0 GROUNDWATER BALANCE

After the understanding the groundwater flow pattern in Ahwar area, water balance could

be calculated taking into account all identified groundwater sources. AHWAR Delta

consists of the flood plain of Wadi Ahwar. The plain consists for the most part of alluvial

fan areas which, are mainly developed for groundwater agriculture, near the foothills in the

east rain fed agriculture and some hills runoff agriculture take place. Spate irrigation can

be found along upper streambed of the Wadi, groundwater irrigation mainly concentrated

at the center of. Ahwar plain. Except for some runoff from hill slopes in the foothills, no

runoff is generated in Ahwar Delta. The Delta is considered a runoff absorbing area. The

flow seeps down to the wadi courses in AHWAR area causing direct recharge to the

aquifer, the annual average wadi flow of (65.8 Mm3) causing direct recharge to the delta

aquifer system. The estimated amount of annual recharge through wadi flow is presented in

the runoff water balance sheet.

Despite of upstream spate irrigation, large surface flow is still available at wadi Ahwar

delta. While groundwater natural inflows to the basin are increasing gradually with

groundwater slope and the slope increases together with drawdown and /or abstraction

from the basin, the inflows then were calculated as percentages from the actual abstraction,

more abstraction means more irrigation and more return flow. The total abstraction was

calculated at 24 Mm3 according to the analyzed results of the surveys conducted by the

project. .

The annual rainfall in the area varies between 60 mm along the coast and 100 mm at the

edge of the foothills. The average rainfall is in the order of 80mm. The direct recharge

from rainfall was estimated to 5% of the average rainfall or 0.6 MCM of direct recharge

over the study area. This amount was not considered in the water budget.

The groundwater loss by evaporation is considered equal to 9.7 Mm3. This is based on

Kazgiprovodkhoz Institute (1990) evaluation.

Irrigation return flow coefficients, is the ratio between the quantities of water returned

from the cultivated area to the groundwater system and the amount of abstraction is

considered equal to 25% of the total amount of irrigation water diverted through spate

irrigation.

Groundwater level elevations in AHWAR area have dropped down in many places forming

depleted cones. The groundwater flow pattern has been changed and lateral flow has

occurred. Based on the depleted cones, this lateral flow was calculated at 3 % of the total

annual abstraction. This figure was driven from Darcy’s law. Groundwater approximate

gradient and aquifer permeability estimated at 6m/d, based on pumping tests results, and

assuming an average saturated thickness of 30 m of the aquifer in the north and 15m in the

south.

The detailed groundwater budget for the period 1999 to 2007 is provided in table 9.1

below.

The ground water yearly deficit is about 15 Mm3 annually, the deficit is accumulated

yearly, and increasing water abstraction will lead to more groundwater depletion and will

invite seawater intrusion.

The safe yield of the groundwater system is estimated at 18.66 Mm3

Table 2.3 Groundwater budget Wadi Ahwar *)

Year Runoff Irrigation

from Irrigation

to ground

water

Wadi loss

to ground

water

Lateral

inflow

Total IN

(4+5+6)

Abstrac-

Tion

Evapora-

tion

total OUT

(8+9)

Yearly balanc

e

(7-10)

1 2 3 4 5 6 7 8 9 10 11

1999 101.12 56.01 14.00 11.79 0.72 26.51 24.00 9.70 33.70 -7.19

2000 50.50 39.54 9.88 5.54 0.72 16.14 24.00 9.70 33.70 -17.56

2001 76.97 58.82 14.71 8.36 0.72 23.79 24.00 9.70 33.70 -9.91

2002 53.57 38.10 9.53 5.87 0.72 16.11 24.00 9.70 33.70 -17.59

2003 1.16 1.10 0.28 0.06 0.72 1.05 24.00 9.70 33.70 -32.65

2004 14.29 10.46 2.62 1.49 0.72 4.83 24.00 9.70 33.70 -28.87

2005 41.72 36.30 9.08 4.30 0.72 14.10 24.00 9.70 33.70 -19.60

2006 188.15 90.74 22.69 22.40 0.72 45.81 24.00 9.70 33.70 12.11

2007 64.65 47.78 11.95 6.98 0.72 19.64 24.00 9.70 33.70 -14.06

averages 10.52 7.42 18.66 33.70 -15.04

*) values in columns 2 – 11 in Million Cubic Meters (MCM)

9.0 GROUNDWATER MONITORING

9.1 Monitoring Approach

addressing monitoring frequency requirements with respect to saltwater intrusion and the

movement of salinity from the southern direction, addressing the effects of elevated iron

concentration in groundwater and the effect upon irrigation efficiency and pumping

efficiency,

The monitoring network for the Delta groundwater management unit consists of a number

of observation bores/one observation well/50km2, with a proposed bi-annual to monthly

monitoring frequency and includes two automatic data loggers.

A number of observation bores within the Delta should be specifically constructed to

locate the fresh/salt water interface and monitor the movement of the saltwater wedge.

These particular observation bores have continuously slotted casing which enables

monitoring to consist of conductivity readings recorded at 1 m intervals from the water

level to the base of the bore. The groundwater monitoring network within the Delta should

be adequate for the detection of seawater intrusion or a marked rise in the water table, and

observation bores should continue to be measured for water level, major ions, pH, and

conductivity and salinity movements.

Monitoring of water levels and complete water quality (including nutrients) is essential to

the management facilitating integration between surface water and groundwater resources,

and enabling swift management response to changes in water quality.

9.2 Groundwater monitoring network

Eight monitoring well sites were selected to reflect the actual groundwater movement,

abstraction and water quality variations, 5wells were selected along the groundwater path

from the Delta recharging point in the north to the discharging point in the south to

represent the actual ground water conditions, two wells were selected to be close to the

coast to track the water quality variation and the possible seawater intrusion, Figure 7.

Figure 7 Location of Monitoring Wells

Two other wells were selected in the eastern part of the Delta to monitor the groundwater

depletion between the pumping wells.

References

1. Ministry of Agriculture and Irrigation. “Wadi Ahwar, feasibility study”

Hydrosult INC, 2006, Ministry of Agriculture and Irrigation.

2. Ministry of Agriculture and Irrigation Integrated Rural Development project

for Middle Plateaus. “Feasibility Study for A gricultural Development in

Aryan Governorate (draft final report” March 2006.

3. Ministry of Agriculture and Irrigation General Directorate of Irrigation.

“Updating the Feasibility Study and Detailed Design, Delta Aryan Dams

project, Final Report Phase 1”, August 2004.

4. Ministry of Agriculture and Irrigation, Irrigation Improvement Project.

“Quarterly Progress January – March 2006, PIU – Tuban March 2006.

5. Ministry of Agriculture and Irrigation, Irrigation Improvement Project.

“Accumulative Report – July – June 2006, June 2006.

6. Ministry of Agriculture and Irrigation, Irrigation Improvement Project,

Project Management Unit. “Agricultural Development Component (Wadi

Zabid and Wadi Tuban) Quarterly Report January – March 2006” ,

Agronomy Consultant March 2006.

7. Ministry of Agriculture and Irrigation, Irrigation Improvement Project,

Project Management Unit. “Agricultural Development Component (Wadi

Zabid and Wadi Tuban) Quarterly Report April – June 2006, Agronomy

Consultant June 2006.

8. Ministry of Agriculture and Irrigation, Wadi Hadramout improvement

project March 2008