Land Resource and Hydrological Inventory of Chik Bamanhal Sub-watershed for Watershed Planning and Development Koppal Taluk, Koppal District, Karnataka (AESR 3.0)

Abstract

The average annual rainfall of 631 mm in the Chik Bamanhal sub-watershed as recorded from the Koppal station data. 65%, 20% and 15% of the annual rainfall occurs during Kharif, Rabi and Summer seasons respectively and exhibited a higher temporal variability. The evapotranspiration estimation tool developed indicates that the watershed water balance is in deficit .The cropping & irrigation choices are not appropriate and need to be altered to shift the deficit water balance. The estimated runoff available to use is 56 mm for an average annual rainfall of 596 mm (2009-2017). The utilizable groundwater is 30.8 mm (70% of 44 mm recharge estimated). This means the total available water resource combining the soil moisture store for kharif & rabi (178 mm) and utilizable runoff plus recharge is 265 (=178+56+31) The average actual evapotranspiration estimated in the watershed based on the current land use and irrigation practices for the kharif and rabi seasons is 493 mm. Hence the amount of water use for kharif and rabi seasons may be estimated as 616 mm (i.e. 125% of AET). This demand for the two seasons is higher by 351 mm, i.e. (616-265). The AET in June-Sept months is almost 72% of rainfall. Hence, there is slightly less opportunity to harvest the excess water through watershed management practices for utilizing during rabi season. The total number of wells present in Chik Bamanhal Sub-watershed as per LRI data is 123 (123-Borewells). The groundwater level shown above is from the data obtained from Dept. of Mines & Geology for the nearest station Kanakagiri.