Land Resource and Hydrological Inventory of Bannikoppa 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 Bannikoppa sub-watershed as recorded from the Alvandi station data by KSNDMC. 60 percent, 21 percent and 19 percent 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 2.25 mm for an annual rainfall of 584 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 (216 mm) and utilizable runoff plus recharge is 249.05 mm (=2.25+216+30.8). The average actual evapotranspiration estimated in the watershed based on the current land use and irrigation practices for the kharif and rabi seasons is 812 mm. Hence the amount of water use for kharif and rabi seasons may be estimated as 1015 mm (i.e 125% of AET). This demand for the two seasons is marginally higher by 766 mm, i.e. (1015-249.05). The AET in June-Sept months is more than the 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 Bannikoppa Sub-watershed as per LRI data is 5 (4-Borewells & 1-Openwells). The groundwater level was found from the data obtained from KSNDMC for the nearest station Irkalgad. The groundwater levels during the years 2008-2017 was almost constant except May- 2017.