Assessing impacts of agricultural water interventions in the Kothapally watershed, Southern India

Abstract

The paper describes a hydrological model for agricultural water intervention in a community watershed at Kothapally in India, developed through integrated management and a consortium approach. The impacts of various soil and water management interventions in the watershed are compared to no-intervention during a 30-year simulation period by application of the calibrated and validated ARCSWAT 2005 (Version 2.1.4a) modelling tool. Kothapally receives on average 800 mm rainfall in the monsoon period. 72 per cent of total rainfall is converted as evaporation and transpiration (ET), 20 per cent stored by groundwater aquifer and eight per cent exported as outflow from the watershed boundary in current water interventions. ET, groundwater recharge and outflow under no intervention conditions are found to be 64 per cent, nine per cent and 19 per cent, respectively. Check-dams helped in storing water for groundwater recharge, which can be used for irrigation, as well minimizing soil loss. In-situ water management practices improved the infiltration capacity and water holding capacity of the soil, which resulted in increased water availability by 10-30 per cent and better crop yields compared to no intervention. Water outflows from the developed watershed were more than halved compared to no intervention, indicating potentially large negative down-stream impacts if these systems were to be implemented on a larger scale. On the other hand, in the watershed development program sediment loads to the streams were less than one tenth. It can be concluded that the hydrological impacts of large scale 2 implementation of agricultural water interventions are significant. They result in improved rain-fed agriculture and improved productivity and livelihood of farmers in upland areas while also addressing the issues of poverty, equity and gender in watersheds. There is a need for case specific studies of such hydrological impacts along with other impacts in terms of equity, gender, sustainability and development at the meso-scale.

Agricultural groundwater management in the Upper Bhima Basin, India: current status and future scenarios

“…The challenge is to deliver WSD in a way that is technically and economically effective, whilst taking into account of the water requirements of downstream areas. Garg et al (2011b) reports that in the Kothapally micro-watershed of the Musi sub-Basin, the surface water outflow was reduced by more than 50 % after the implementation of the watershed development programme. When such treatments are applied in a widespread fashion, Garg et al (2011b) demonstrated that this has significant implications on downstream flows to the Osman Sagar reservoir that provides supply to Hyderabad (the sixth biggest city in India).…”

“…Major WSD programs are undertaken to counter groundwater over-exploitation (as well as soil erosion) across the drier rainfed areas of India, including within the Upper Bhima (Garg et al, 2011b). Modelling the anticipated expansion in WSD first requires an estimate of the sub-basin's excess surface water that is available for harvesting.…”

A Simple and Farmer-Friendly Decision Support System for Enhancing Water Use Efficiency in Agriculture:Tool Development, Testing and Validation

“…Check dams and water harvesting storage structures play an important role in augmenting water resources at community or village scale. Garg and co-workers 15,16 showed that constructing small and medium water harvesting structures in watershed could harvest 30-60% of runoff water and enhance groundwater recharge in a semi-arid tropical regions. Water harvesting storage capacity developed in a given watershed or landscape could be provided on per hectare basis in WIC.…”

Governance and management of local water storage in the Hindu Kush Himalayas

“…While rainwater harvesting in watersheds may help in increasing water availability for upstream farmers, in some cases it may hurt the downstream farmers; an assessment in a semi-arid watershed in Andhra Pradesh found that water-flows out of a developed area declined significantly, hurting the downstream users (Garg, Karlberg, Barron, Wani, & Rockstrom, 2011). If water storage systems upstream result in reduced water availability to communities downstream, these communities may have to be compensated by the upstream beneficiaries.…”