Myths about Small Water Harvesting Systems

Abstract

We are writing in response to the article by M Dinesh Kumar, Ankit Patel, R Ravindranath, O P Singh “Chasing a Mirage: Water Harvesting and Artificial Recharge in Naturally Water-Scarce Regions” (EPW, 30 August 2008). The authors have argued that runoff water harvesting does not offer any potential for groundwater recharge or for improving water supplies at the basin scale. They have, thus, concluded that the investments made on this sector are a colossal waste of scarce resources and also cause several negative social and environmental consequences. However, in the conclusion they say, “The foregoing analysis does not suggest that water harvesting and groundwater recharge systems do not generate benefits”, thus indicating an iota of doubt. In the process of analysis, some of the implicit underlying assumptions made by authors include: (1) Comparison of annual rainfall with annual reference/potential evapotranspiration is the guiding principle/indicator for runoff water harvesting. (2) Water harvesting is essentially and in all instances meant for groundwater recharge. (3) Runoff is the amount in excess of the soil moisture storage and infiltration. (4) Watershed programmes only have problems of quality of implementation. (5) Water harvesting systems are, by and large, designed to capture the entire runoff and state government and central developmental agencies alongwith nongovernmental organisations (NGOs) are promoting the concept. (6) The existing storage and diversion capacities in river basins is close to utilisable flows. (7) Water harvesting necessarily has to be profit-oriented and in order to make it happen it has to be utilised for high value crops. (8) Reliability of supplies from water harvesting systems is very poor in arid and semi-arid regions of India, which are characterised by low mean annual rainfalls, very few rainy days, high inter annual variability in rainfall and rainy days and high potential evapotranspiration. (9) In order to call water harvesting systems profitable, the incremental benefits by water harvesting systems have to be beneficial at basin scale but not at the local level. In the light of these assumptions and the consequent analysis branding water harvesting systems as ineffective, we would like to offer our comments. India has a long history of water harvesting which has been neglected after the creation of large storage structures and popularisation of borewell technology. However, the revival of the water harvesting systems by individuals, NGOs, and developmental agencies, has led to their importance being recognised particularly in arid and semi-arid rainfed areas. Water harvesting systems were started as part of catchment area treatment in river basin projects to act as complementary storage structures and to reduce the silt movement which otherwise would reach the reservoir leading to siltation and reduction in effective storage over a period of time.