Water Harvesting and Water Harvesting and Groundwater Recharging in India:Groundwater Recharging in India:

Potentials and PitfallsPotentials and Pitfalls

M. Dinesh Kumar, B. R. Sharma, Ankit Patel and OP Singh

IWMI-Tata Water Policy Research Programme

Water Management in Basin ContextWater 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 WaterSupply 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

69.0 53.730.1

279.3

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73.142.9

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Per Capita Net Sown Area (UCD) Per Capita Net Sown Area (LCD)

Wells are overflowing!Figure X: Water Level Fluctuation in Wells in Fulzar, Ghelo River

Basin

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Rainfall, mm Nr-Median Far-Median

Effect of Watershed Interventions on Effect of Watershed Interventions on Run-Off Run-Off

G-S Rainfall-Runoff, Cms

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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

Total Rainfall, Cms Total Roff, Cms

Marginal cost & benefits of water harvesting with different stages of basin development

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Marginal benefit (Social, Environmental and Economic)

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Degree of Water Development

Wet Year

Dry Year

Mean Annual Rainy Days

Increasing unit cost for higher runoff collection

Trade off between Economics and Hydrological Opportunity

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