Presented by IWMI's Lal Muthuwatta at the 3rd International Conference on the Status of Future of the World's Large Rivers, April 18 - 21, 2017, New Dheli, India.

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Water for a food-secure world
Regional suitability assessment for Underground
Taming of Floods for Irrigation (UTFI)
Lal Muthuwatta1, Pennan Chinnasamy1, Nishadi Eriyagama1,
Karthikeyan, Brindha3, Paul Pavelic2
1 International Water Management Institute, Colombo, Sri Lanka.
2 International Water Management Institute, Lao PDR.
3 Department of Civil and Environmental Engineering, National University of Singapore,
Singapore.
Photo by Neil Palmer / IWMI

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Water for a food-secure world
Suitability index
• Regional-scale mapping and verification of hotspot areas
for implementation
• First step - selection of suitable site for piloting
• Method devised to choose site
• Data collected from IWMI database & open source
• Analysed using GIS tools

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Water for a food-secure world
The Approach

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Water for a food-secure world
SI for the Ganges basin
Category
SI
Area (sq km) %
Low
57,953.4 13.4
Moderate
72,047.9 16.6
High
188,674.2 43.5
Very high
105,311.5 24.3
Data not available
9,380.0 2.2
Total
433,367.0 100.0
Total: 861 watersheds

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Water for a food-secure world
SI for UTFI in different states
State
Area under different SI (%)
Low Moderate High Very
high
Bihar 1.5 10.8 47.5 40.2
Uttrakhand 79.0 12.5 8.2 0.2
Uttar Pradesh 1.0 10.5 60.1 28.3
West Bengal 5.3 7.7 31.5 55.5
Madhya Pradesh 10.1 34.8 28.2 26.9
Jharkhand 11.4 53.5 30.9 4.2

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Water for a food-secure world
Semi-coupled modelling framework (2)
Ramganga sub-basin
Population - 15.7 million (in 2011).
Agriculture is the primary livelihood
activity, followed by industrial and
timber marketing activities.
The major crops are paddy, wheat,
sugar cane and cash crops, grown in
three season: the Rabi (November to
March), Kharif (June to October) and
Zaid or hot weather (March to May)
seasons.
Area – 18,667 km2
Elevation – 122 – 1446 amsl
PET 1278 mm.
MAR - 923 mm (575 – 1686).

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Water for a food-secure world
Sub-regional scale hydro-dynamic modelling of surface
water and groundwater systems for cases with and
without UTFI:
• To understand the baseline hydrologic conditions.
• To assess the interactions of surface water and groundwater.
• To test scenarios with UTFI interventions.
Semi-coupled modelling framework (1)

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Water for a food-secure world
Semi-coupled modelling framework (3)

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Water for a food-secure world
Model inputs

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Water for a food-secure world
Scenarios
• Baseline
• Utilization of barren land to enhance groundwater recharge
• Reduction of land use runoff values to enhance
groundwater recharge
• Reduction of outflow discharge from the basin:
A total of 5 sub-scenarios with different level of
recharge were introduced in the model so that the
outflow discharge is reduced, through storage in
MARs, by 10%, 20%, 30%, 40% and 50%.

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Water for a food-secure world
Results (1) Surface flows
Average annual out flow – 6.8 Bm3
Out flow ( July – September) – 5.9 Bm3
0.00
0.50
1.00
1.50
2.00
2.50
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecFlow(Bm3)
Month
0.00
2.00
4.00
6.00
8.00
10.00
12.00
0.07 0.14 0.21 0.29 0.36 0.43 0.50 0.57 0.64 0.71 0.79 0.86 0.93 1.00
FLOW(BM3)
PROBABILITY
Exceedance Probability

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Water for a food-secure world
Results (2) Change in Flood Return Period
A 20% reduction in
discharge at outlet
will convert:
• 15 year return
period flood to an
8 year one
• 5 year return
period flood to a 3
year one
• 2 year return
period flood to a 1
year one
0
250
500
750
1000
1250
1500
1750
2000
2250
0 4 8 12 16
Discharge(m3/s)
Return Period
Baseline
10% reduction
20% reduction
30% reduction
40% reduction
50% reduction

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Water for a food-secure world
Results (3) Change in Inundated Extent
Reduction in Inundated extent under a 15 year return period
flood due to a 50% reduction in flow
50% flow red.
24 % reduction in
inundated extent

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Water for a food-secure world
Results (4) Change in Inundated Extent
Return
Period
(years)
Area (Thousand Ha)
Baseline
10%
reduced
flow
20%
reduced
flow
30%
reduced
flow
40%
reduced
flow
50%
reduced
flow
2 108 103 97 93 87 80
5 118 112 104 100 93 86
15 141 135 127 122 115 107
• A 20% flow reduction results in a 10% reduction in inundated
extent under all return periods.
• A 20% flow reduction will reduce the water level at the
Ramganga outlet under a 15 year flood by 0.45 m.

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Water for a food-secure world
Results (5) Groundwater levels
230
232
234
236
238
240
242
244
246
248 Jun/99
Dec/99
Jun/00
Dec/00
Jun/01
Dec/01
Jun/02
Dec/02
Jun/03
Dec/03
Jun/04
Dec/04
Jun/05
Dec/05
Jun/06
Dec/06
Jun/07
Dec/07
Jun/08
Dec/08
Jun/09
Dec/09
Jun/10
GroundwaterElevation(m)
(a) Months
Baseline 50% 30%
• All sub scenarios indicate a trend in which the groundwater
levels stabilize and find new equilibrium levels.
• In some cases (e.g. 50% flow reduction) the groundwater
trends stabilize and increase.

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Water for a food-secure world
Concluding remarks (1)
• Site selection- an integral step to identify target
watersheds is proposed.
• Results help to prioritize investments.
• Tool for decision makers to execute mitigation measures
for large scale benefits.
• Approach directly transferable to other river basins.

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Water for a food-secure world
• The introduction of distributed structures across the
basin leads to reduction of basin outflow and
improvement of groundwater levels.
• Groundwater levels gradually improved after a 5 year
period, resulting in a reversal of groundwater depletion
trend.
• Peak flow reductions result in lowering the magnitude
(i.e. return period, inundated area) of current floods.
Concluding remarks (2)