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 km 3  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 Low rainfall, high variability in water scarce areas  Fewer rainy days in semi arid and arid, water scarce areas Fewer rainy days in semi arid and arid, water scarce areas  Evaporation rates are high in water scarce regions Evaporation rates are high in water scarce regions  Large part of India has hard rock geology 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 Scale considerations in economic evaluations  Trade off between economics and hydrological benefits 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 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 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 Mean Annual Rainfall

Average Annual Evaporation Average Annual Evaporation

Aquifer System in India

Stage of Storage Creation in Some Major River Basins in India Stage of Storage Creation in Some Major River Basins in India

Upstream Vs Downstream Water Demand Upstream Vs Downstream Water Demand

Wells are overflowing!

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

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

Mean Annual Rainy Days

Increasing unit cost for higher runoff collection