Rainfall trends and drought variability over last 119 years in the Damodar river basin, Eastern India

The present paper intends to show the effect of the climate change on trend and pattern of rainfall and the drought intensity assessment over the Damodar basin eastern part of Indian subcontinent. In this study we have divided into two parts. First phase entails of an analysis of the rainfall trends in annually, monthly and seasonally over the 12 stations in the basin region for the period 1901 to 2019. The trend pattern was determinant by non-parametric Mann-Kendall (MK) significance was tested through Sens slope and Sequential Mann-Kendall (SQMK) test has been applied to identify change point of annual precipitation. The second part of this study intricate the drought assessment through standardised precipitation index (SPI) and percent departure from normal rainfall (PDNIMD) statistics analysis. The rainfall trend results shows that last 119 years negative significant trend is found at Chatra (-0.16mm/yr), Latehar (-2.69mm/yr) and Ranchi (-2.71mm/yr) stations in the upper domain of Damodar basin. But in the lower domain Hooghly station displayed highest positive change in monsoonal magnitude (+0.28mm/yr) rainfall during 1901-2019. The most probable change point years in rainfall i.e., 1963, 1982; 2004 and 2018 have been observed for the rainfall station in upper and lower region of the Damodar basin. As a result the SPI and PDNIND in the worst drought years of 1935, 1958, 1976, 1979, 1992, 2005, 2009, 2015 and 2018 in the low rainfall district indicated only moderate to extreme dryness. The results highlights that in certain years, local variables such as El Nino and Sea surface temperature (SST) have a greater influence on drought occurrence and non-occurrence in Damodar river basin than global causes such as El Nino and the Southern Oscillation (ENSO).