Transcript Managing River Basin - International Water Management

Water Harvesting and
Groundwater Recharging in India:
Potentials and Pitfalls
M. Dinesh Kumar, B. R. Sharma, Ankit Patel and OP Singh
IWMI-Tata Water Policy Research Programme
Water Management in Basin Context
 Supply management
 Building large water storage/diversion systems
 Decentralized WH
 Inter-basin water transfers
 Demand management
 Improving water use efficiency
 Allocation to economically efficient uses
 Inter-sectoral water allocation
 Inter-regional water allocation
 Water resource and ecosystem management
Supply Side Management of Water
 Uneven distribution of water
 Across basins
 Within basins
 India has built many large water resource systems
 250 km3
 Concentration of storages in water-deficit areas
 Basins in water scarce areas are “closed”
 Water rich areas have poor demand
 Inter-basin water transfers
Water Harvesting and Groundwater
Recharge in India
 Objectives



Improve runoff collection and
storage efficiency
Equitable distribution of water
Resource management
 Underlying value

Local water self sufficiency;
demands are small
 Assumption


More structures mean more
benefit
Structures are cost-effective
 Community-based,
decentralized planning &
action
Supply-Demand Issues in Rainwater
Harvesting
 Low rainfall, high
variability in water
scarce areas
 Fewer rainy days in
semi arid and arid,
water scarce areas
 Evaporation rates are
high in water scarce
regions
 Large part of India has
hard rock geology
Supply-demand issues in rainwater
harvesting
 Runoff intensities high and inter-annual
variability high
 Water rich Cauvery
 Water scarce north Gujarat
 Soil infiltration capacities
 High water demand in water scarce areas
Economic Issues in Water Harvesting
 Difficulty in estimating the unit costs
 Lack of data on inflows
 Lack of data on collection and storage efficiencies
 Scale considerations in economic evaluations
 Trade off between economics and hydrological
benefits
Issues related to improving basin water
economy
 Demands higher in lower plains of river basins; supply
potential is high in upper basin areas
 Economic value of water high in scarce areas
 Lack of integrated approach to planning

Groundwater contributing to surface flows in hilly areas
 Lack of water use planning for harvested water
 Local Vs Basin Impacts in closed basins


Downstream impacts of water harvesting in Narmada basin
Downstream negative impacts in Ghelo river basin,
Saurashtra
Findings
 Limited potential of RWH in demand –
supply imbalance
 low mean annual rainfalls, high inter-annual
variability, high PET & E
 Inefficient recharging in hard rocks
 Many water-scarce regions have
water demands, far exceed the
supplies
Findings
 Scale considerations for cost and
economics of WHS
 ‘Closed’ & ‘Open’ basins
 U/S diversions reduce prospects of D/S
 Future research in WH include
 Potential impacts of WH on large water
resource systems in basins
 Optimal level of WH & development in
different river basins without any
downstream impacts
How to make water harvesting more
effective?
 Understand catchment hydrology better
 Use of hydrological simulation models for
un-gauged basins
 Use of remote sensing and GIS to generate
geo-morphological data for simulation
models
 Focus on green water, harvested in RWHS
 Collection efficiency
 Use efficiency
How to make water harvesting more
effective? Cont…
 Study basin water accounts and
water balance
 How much water is used up as beneficial ET,
non-beneficial Evaporation
 How much surplus flows available for
harnessing
 Improve wet water-saving in water
harvesting structures and large
water resource systems
 Develop proper water use plans for WHS as
well
Conclusions
 Water harvesting/watershed programmes to be
supported by proper understanding of basin
water accounts and balance
 Developing proper water use planning before
harvesting initiatives is important
 Research on long term impacts of water
harvesting is important. It should take into
account the “scale factor”, and cover
hydrological and economic imperatives.
Thank you for the attention
Average Mean Annual Rainfall
Average Annual Evaporation
Aquifer System in India
Stage of Storage Creation in Some
Major River Basins in India
300.00
279.3
250.00
165.5
200.00
150.00
100.00 36.0 33.4
57.3
75.0
49.7 50.4
50.00
79.5
73.1
0.0 42.9
69.0 80.8
53.7
68.6
30.1
8.6
EFR
Between
EFR
Between
WFR of
Kachchh and
Mahi
Tapi
Pennar
Godavari
BrahmaniBaitarani
Meghana
(Barak) Sub-
Ganga SubBasin
Indus
0.00
Upstream Vs Downstream Water
Demand
0.5
PET/Rainfall
3
0.4
2.5
2
0.3
1.5
0.2
1
0.1
0.5
0
0
Sabarmati
Indus
Narmada
Cauvery
Krishna
Mahanadi
PET/R (UCD)
PET/R (LCD)
Per Capita Net Sown Area (UCD)
Per Capita Net Sown Area (LCD)
Per capita Net Sown Area
3.5
Wells are overflowing!
Effect of Watershed Interventions on
Run-Off
G-S Rainfall-Runoff, Cms
140
120
Total Rainfall, Cms
Total Roff, Cms
100
80
60
40
20
0
66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 0 1 2 3 4 5
Year
Marginal Cost/ benefit
Marginal cost & benefits of water harvesting
with different stages of basin development
Marginal benefit (Social,
Environmental and
Economic)
Wet Year
Dry Year
O
Degree of Water Development
Wet
Year
r
Mean Annual Rainy Days
Increasing unit cost for higher runoff
collection
Trade off between Economics and Hydrological
Opportunity
0.25
Rs.
0.20
0.15
0.10
0.05
0.00
1
MCM
3
11.89