Estimation of Drought Indices for Assessing the Impact of Climatic Variables on Groundwater Fluctuation over Upper Bhima Sub Basin

Abstract

Groundwater is an essential part of the hydrological cycle. The ultimate source of the groundwater is precipitation that occurs over the surface of the earth. Stress condition in groundwater reflects the vulnerability of drought events. In areas with ample soil moisture and without irrigation facilities, groundwater abstraction eventually leads to a decrease in agricultural yield. For the assessment of groundwater fluctuations, hydrological drought indices play a significant role in drought conditions. In Upper Bhima sub-basin, maximum area is under scarcity zone and partly under assured rainfall zone (Western part) and partly in transition zone I & II (Western part) with average annual rainfall of 690 mm. In the present study, standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI) and standardized water level index (SWI) is used to assess meteorological and hydrological drought conditions respectively. As SWI reflects aquifer stress, it is also used to understand groundwater decline and recharge in the present study region. SPI and SPEI are estimated by using precipitation and temperature data for yearly aggregated time scale, while SWI is obtained by normalising groundwater level data. Precipitation and temperature data are obtained from gridded reanalysis data product of NCEP – CFSR (spatial resolution approx. 38 km) for the period of 2002-2014. Groundwater level data is obtained from Central Ground Water Board for the period of 2002-2016. Spatio-temporal map of SPI, SPEI and SWI has been generated. No direct linear relationship has been observed between SPI and SWI; and between rainfall and SWI over the region. Hence, topography, aquifer properties, soil type and lithology may affect groundwater fluctuation in the region.