Assessment of Hydrological Changes in Godavari River Basin Under the Impacts of El-Niño

Abstract

El Niño–Southern Oscillation (ENSO) is the most prominent driver of the inter-annual variability of Indian summer monsoon rainfall (ISMR). This study focuses on understanding the hydrological variations in Godavari River Basin (GRB) due to the weakening of ISMR during El Niño years (1980–2008), using the variable infiltration capacity (VIC) model. The entire basin was discretized into 1325 uniform grids of resolution 0.15°×0.15° (about 16.65 km), and hydrological parameters of the basin were analysed at each grid level for various El Niño events. Based on the Oceanic Niño Index (ONI), obtained from National Oceanic and Atmospheric Administration (NOAA), El Niño events occurred in the past were subclassified into weak (2004 and 2006), moderate (1986, 1994 and 2002), strong (1987 and 1991) and very strong (1982, 1987) events. For this study, VIC model was run for the period 1980–2008 and a composite of El Niño and normal years (1981, 1985, 1989, 1990, 1992, 1993, 1996, 2001 and 2003) was prepared to assess the impacts of El Niño events on the hydrology of GRB. Our results showed a negative correlation of precipitation, abstractions and soil moisture with the increasing magnitude of El Niño events. The quantum of precipitation was reduced during El Niño years compared to normal years, which showed the basin's exposure to more frequent droughts during El Niño events.