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Paper presented in "National conference on water, food security and climate change (cc), 23-24 November 2011, Kathmandu, Nepal.
Citation preview
Water for a food-secure world
P. Gurung and L. Bharati
International Water Management Institute (IWMI), Lalitpur, Nepal
Downstream impacts of the Melamchi Inter-basin Water Transfer Plan (MIWTP) under current and
future climate change projections
Water for a food-secure world
Background
Melamchi Water Supply Project (MWSP):
1973 (Identified) 1998 (Implemented)
2008 (Planned to Complete) 2015 (Extend to Complete)
Demand of local people, political circumstances and challenges to engage
private sector partner is major barrier to complete project
Drinking Water Demand of Kathmandu: 220 MLD
Water available in Kathmandu Valley: 90 MLD (Dry Season)
130 MLD (Wet Season)
In addition, downstream hydrological impacts is another issue
(Project has set minimum downstream release nearly 35 MLD)
Water for a food-secure world
Objective of the Study
1. Use of distributed hydrological model developed for entire Koshi basin
to look hydrological impacts of the MIWTP until the outlet of the Koshi
basin at Chatara
2. To evaluate impact of climate change on downstream hydrology under
current and future climate scenario
3. To quantify impact of water transfer on agricultural command area of
Melamchi river (289 hectare) under current and future climate scenario
Water for a food-secure world
Model used for the Study
Soil Water Assessment Tool (SWAT) Model:
- Physically based semi-distributed hydrological model
- To simulate water quantity, sedimentation and water quality
- Developed by Department of Agriculture of USA
Soil, Water and Salt Balance (BUDGET) Model:
- Field based model
- To simulate crop water requirement (CWR) and prepare irrigation
schedule
- Developed by faculty of applied bioscience and engineering, Katholieke
Universiteite Leuven of BELGIUM
Water for a food-secure world
Study River Reach
Ü1
8
6
2
4
3
5
14
9
32
17
51
7
16
78 73
11
18
10
75
12
45
34
27
13
5762
65
58
56
15
38
5560
72
23
71
30
61
53
54
36
6967
44
66
42
35
59 64
40
74
70
19
47
43
4137
68
31
7679
28
48
77
29
39
22
20
46 5249
63
25
50
33
262421
0 60 12030 km
Model developed for Koshi basin is divided into 79 sub-basins (Outlet Chatara)
Water for a food-secure world
Study River Reach
Ü
!(
!(
!(!(
!(
!(
!(
!(
!(
!(!(
!(
!(
!(
!(
!(
!(!(
!(
!(
!(
!(
!(
!(
#*
#*
#*
#*
#*
#*#*
#*
#*
#*
#*
#*
#*
#*#*
78
55
72
61
67
42
35
7679
48
77
22252421
4300
4000
2223
2222
2221
14191406
1404
1325
1324
1307
1303
13011220
1213
1212
1206
1115
1108
11031062
1022
1006
285885
695690
684
681
670652
650647
630
620
668.5
627.5
604.5
0 60 12030 km
LEGEND
#* Flow Station
!( Climate Station
River Netwroks
Melamchi River (Stage-I)
Yangri River (Stage-II)
Larke River (Stage-III)
Study River Reach
Koshi River Basin
Country Boundary
Ü
INDIAINDIA
NEPAL
CHINA
INDIA
Downstream impact of MWSP is carried out for 11 among 79 sub-basins of Koshi basin
Water for a food-secure world
Study River Area
78
55
72
61
67
42
35
7679
48
77
22
24
2125
2225
35
24
21
Study River Reach
Water Transfer Location
In this study, the study river reach starts from sub-basin 35 and ends at sub-basin 79
Water Transfer Location
(I) (II) (III)
Water for a food-secure world
Climate Change Projection Scenario
Global Circulation Model:- Downscaled using MarkSim Weather Generator (http://gismap.ciat.cgiar.org/MarkSimGCM/)- Average of CNRM-CM3, CSIRO-Mk3.5, ECHam5, and MIROC3.2- AR4-SRES: BL, A2 and B1- Period: 2000s (1971-2000) for BL
2030s (2016-2045) for A2 and B12050s (2036-2065) for A2 and B1
- Variable: Rainfall, Temperature (Max & Min), Solar Radiation
Statistical Downscaled:- AR4-SRES: BL, A1B, A2 and B1- Period: (1971-2000) for BL
(2001-2100) for A1B, A2 and B1- Variable: Rainfall, Temperature (Max & Min), Solar Radiation,
Relative Humidity and Wind Speed
Water for a food-secure world
35
48
61
55
67
72
78
77
76
79
42
24
21
Melamchi
Sapta Koshi
Sun Koshi
Rosi
Tama Koshi
Likhu
Dudh Koshi
Arun and Tamor
Water Supply
to
Kathmandu Valley
Stage-II&III: Water Transfer
1.97 m3/s [62.1 MCM]
Stage-I: Water Transfer
1.97 m3/s [62.1 MCM]
Indrawati 22
25
Larke
Yangri
Melamchi Inter-basin Water Transfer Plan (MIWTP)[Conceptual Plan for Modeling]
Conceptual Methods
Stage I: Sub-basin 24 [170 MLD]
Stage II: Sub-basin 25 [85 MLD]
Stage III: Sub-basin 22 [85 MLD]
Order of the sub-basins as per flow direction
The rivers flow intoStudy River Reach
Impact of MWSPoccur in 11 sub-basins
Water for a food-secure world
Monthly Available Water at Headwork of MWSP:
0
50
100
150
200
250
300
350
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mo
nth
ly F
low
Vo
lum
e [M
CM
]
Larke River
Yangri River
Melamchi River
Total Water Transfer Plan
More than 80% of the total annual river flow occurrs within June to October
Result of Current Scenario
Water for a food-secure world
Downstream Impact on River Reach of Koshi Basin:
0.5
1.3
0.6
0.8
0.7
3.9
4.8
77
0.50.2
1.4
0.5
0
12
1.6
3.6
1.6
2.5
1.6
12.7
15.5
1.30.6
4.1
1.3
0 201836 Ü
0.2
2
0.6
0.3
0.4
0.3
2.5
34
0.20.1
0.7
0.2
6
0LEGEND
Dry Season Average Outflow Reduction [%]
Wet Season Average Outflow Reduction [%]
Annual Average Outflow Reduction [%]
0 50 10025 km
Annual Reduction: Stage I : 12%
Stage II : 7%
Stage III : 7%
Wet Season Reduction: Stage I : 6%
Stage II : 4%
Stage III : 3%
Dry Season Reduction: Stage I : 36%
Stage II : 18%
Stage III : 20%
Reduction at Chatara:
Annual : 0.2%
Wet : 0.1%
Dry : 0.6%
Result of Current Scenario
Water for a food-secure world
Current Flow [MCM] CC Projected Range of Flow [MCM]
(1976-2005) 2030s 2050s
Before MWSP:
Melamchi river 499 312 - 347 316 - 359
Yangri river 443 306 - 336 306 - 340
Larke river 448 302 - 342 299 - 349
After MWSP:
Melamchi river 437 250 - 285 253 - 297
Yangri river 412 275 - 305 275 - 309
Larke river 417 271 - 311 268 - 318
Annual Available Water at Headwork of MWSP:
Result of CC Scenario
Water for a food-secure world
Range of Change in Annual Projected Flow at Headwork of MWSP:
Result of CC Scenario
Water for a food-secure world
Range of Change in Wet Season Projected Flow at Headwork of MWSP:
Result of CC Scenario
Water for a food-secure world
Range of Change in Dry Season Projected Flow at Headwork of MWSP:
Result of CC Scenario
Water for a food-secure world
Average Change and Standard Deviation [±µ,(±σ)] in Projected Flow (2030s):
Annual Change: Stage I : -29% (±2%)
Stage II : -29% (±3%)
Stage III : -37% (±1%)
Wet Season Change: Stage I : -33% (±2%)
Stage II : -33% (±3%)
Stage III : -42% (±1%)
Dry Season Change: Stage I : -16% (±4%)
Stage II : -13% (±5%)
Stage III : -19% (±3%)
Change at Chatara:
Annual : - 8% (±25%)
Wet : -15% (±22%)
Dry : +18% (±37%)
Result of CC Scenario
Water for a food-secure world
16 (60)
9 (52)
10 (54)
7 (51)
6 (50)
6 (45)
1 (36)
0 (48)
14 (58)42 (58)
15 (59)
LEGEND
Dry season average change in projected flow [%]
Wet season average change in projected flow [%]
Annual average change in projected flow [%]
0 50 10025 km
Ü
-11 (42)
-4 (50)
-25 (30)
-25 (35)
-25 (31)
-10 (39)
-14 (34)
11 (46)-13 (42)
-10 (47)
-12 (42)
-6 (45)
-1 (51)
-19 (34)
-19 (38)
-7 (40)
-20 (35)
-12 (34)
-8 (45)18 (48)
-8 (48)
-7 (45)
-9 (3)-18 (3)-12 (5)
-15 (5)
-39 (3)-30 (3)
-31 (3)
-26 (2)
-35 (3)-27 (3)
-28 (3)
-23 (2)
Annual Change: Stage I : -28% (±3%)
Stage II : -27% (±3%)
Stage III : -35% (±3%)
Wet Season Change: Stage I : -31% (±3%)
Stage II : -30% (±3%)
Stage III : -39% (±3%)
Dry Season Change: Stage I : -15% (±5%)
Stage II : -12% (±5%)
Stage III : -18% (±3%)
Change at Chatara:
Annual : +18% (±48%)
Wet : +11% (±46%)
Dry : +42% (±58%)
Result of CC Scenario
Average Change and Standard Deviation [±µ,(±σ)] in Projected Flow (2050s):
Water for a food-secure world
Crop
Type 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Paddy 101 150 1 27
Wheat 74 135 30 16
Maize 289 125 1 3
Millet 188 105 16 28
Barley 4 120 15 16
Pulses 47 100 25 16
Oilseed 52 110 4 16
Potato 62 130 9 1
Vegetable 50 105 28 16
MayIrrigated Area [ha]
Cropping Length [Day]
Jan Feb Mar Apr DecJun Jul Aug Sep Oct Nov
Crop
Type 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Early Paddy 161 90 25 22
Main Paddy 289 105 25 7
Wheat 74 120 15 16
Maize 128 105 1 13
Vegetable 215 180 8 11
MayIrrigated Area [ha]
Cropping Length [Day]
Jan Feb Mar Apr DecJun Jul Aug Sep Oct Nov
Existing Cropping Pattern and Calendar
Source: - Field investigation - District Ag. statistics
Possible Change in Cropping Pattern and Calendar
Source: - Field investigation - Proposing by DoI
Cropping Pattern and Calendar of Melamchi River Command Area:
Result – Crop Water Requirement
Water for a food-secure world
Rainfall vs Crop Water Requirement (CWR) in present and change in cropping pattern scenario
Result – Crop Water Requirement
Crop Water Requirement (CWR) of Melamchi River Command Area:
1
10
100
1000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Wat
er D
epth
[m
m]
CWR [Change in Cropping Pattern]
CWR [Present Cropping Pattern]
80% Dependable Rainfall
Irrigation Requirement – Change in cropping pattern
scenario
Irrigation Requirement – Present cropping pattern
scenario
Water for a food-secure world
Comparative plot of water availability and gross irrigation requirement (GIR) in driest month
Result – Crop Water Requirement
Impact of MIWTP on Melamchi River Command Area in Current Climate Scenario:
Water for a food-secure world
Result – Crop Water Requirement
Impact of MIWTP on Melamchi River Command Area in Current Climate Scenario:
Comparative plot of water availability and GIR at 40% overall efficiency in driest month
Intensive Water Use Scenario
Water for a food-secure world
Impact of MIWTP on Melamchi River Command Area in CC Scenario (2030s):
Result – Crop Water Requirement
Intensive Water Use Scenario
Comparative plot of water availability and GIR at 40% overall efficiency in driest month
Water for a food-secure world
Impact of MIWTP on Melamchi River Command Area in CC Scenario (2050s):
Result – Crop Water Requirement
Intensive Water Use Scenario
Comparative plot of water availability and GIR at 40% overall efficiency in driest month
Water for a food-secure world
Conclusion
In past, detail quantification of the impacts in downstream sub-basins have not been done, hence this study help to fill this gap
In this study, flow reduction is quantified in all three stages at sub-basin level under current and future climate projection scenario
In the current scenario, MIWTP will decrease annual water availability by less than 12% on the sub-basin that is immediately downstream of the transfer points but not further downstream towards the basin outlet, the water availability will decrease by 0.2%
THANK YOU !!!
Average climate change result shows that no water stress problem will occur in Melamchi river command area under current and future scenario
Under intense water use scenario, the Melamchi river command area can increase;< 2.2 times of the present area at current climate scenario (< 636 hectare)< 1.4 times of the present area at 2030s climate scenario (< 405 hectare)< 2.0 times of the present area at 2050s climate scenario (< 578 hectare)