Climate change impact assessment on the hydrological regime of palar river basin

Abstract

Climate change is a complex phenomenon and one of the primary environmental challenges that the world is facing today. The two most important regional impacts of climate change are floods and droughts. The amount and patterns of precipitation with an increase in temperature are affecting the hydrological cycle. The study evaluates the impact of future climate change in hydrological regime of the Palar river basin, Tamilnadu, India. The analysis has been carried out in the study area to understand the suitability of groundwater quality for irrigation and drinking purposes. Non-parametric modified Mann-Kendall test has been applied to the historic climate variables such as precipitation, minimum and maximum temperature to detect the trends and Sen slope to determine the magnitude. The NASA Earth Exchange - Global Daily Downscaled Projections (NEX-GDDP) high resolution statistically downscaled future climate dataset has been used for the hydrological simulation under Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 scenarios. The study area of about 15% in the year 2021 and 30% in the year 2022 are in the good to excellent category for drinking purposes. The soil permeability index has overwhelmed the effect of the electrical conductivity, sodium adsorption ratio, soluble sodium percentage, magnesium adsorption ratio and Kelly s ratio that surpassed the permissible limit in groundwater for irrigation usage. The average magnitude of precipitation variation over 120 years (1901-2020) has reduced by 0.148 mm/year. The average extent of the minimum and maximum temperature variation over 30 years has increased by 0.008 °C/year and 0.001 °C /year respectively. Performance criteria analysis by Taylor s diagram and efficiency criteria determined that MIROC ESM GCM is the best fit climate model that represents the climate conditions of the study area. In the RCP 4.5 scenario, the annual rainfall shows an increasing trend and at the end of 21st century, 75 mm increase in average rainfall will be observed in all the