Blue and green water quantification for sustainable water resources management in Kothakunta sub-watershed, Andhra Pradesh

Ground water is an important source for irrigation and drinking water in many parts of Andhra Pradesh. Over exploitation through indiscriminate pumping of water has led to aquifer depletion and ground water contamination causing agriculture vulnerable in rainfed areas. Kothakunta sub watershed in Wargal mandal having an area of 512.5 ha in Medak district is one such area where 98% of ground water resources have already been exploited. Hence, reliable estimates of water balance are necessary for sustainable water resources which can be achieved only through perfect modeling techniques. Soil and Water Assessment Tool (SWAT) is one such model which can be used to quantify the impact of land management practices on the water yield of the watershed with varying soils, land use and management conditions over long period of time. The model quantifies different components of water balance components. Surface runoff, lateral flow and ground water contribution to stream flow account for blue water resources whereas actual evapotranspiration and soil moisture storage indicate green water resources of the watershed. The precipitation and irrigation that was applied was apportioned into different water balance components in which percolation has amounted to 554.98 mm followed by actual evapotranspiration as 540.1 mm, total aquifer recharge as 536.23 mm, surface runoff as 90.32 mm and lateral flow as 32.87 mm. The cultivation of paddy has shown significant impact on water balance components by simulating more runoff (153.15 mm), ground water contribution towards stream flow (250.68 mm) and actual ET of 1225.2 mm, respectively.