Effect of Climate Change on Rainfall Trend in Krishna River Sub-Basin, Andhra Pradesh using SDSM

Abstract

The frequent and irregular change in climatic condition, known as climate change significantly affects many hydrologic events like the precipitation rate, its frequency, runoff, and the water flow in the rivers stream. The significant change in theses hydrologic events, cause an adverse effect on the people around the world. So, it is necessary to study the changing pattern of these climatic events to reduce the future hydro-climatological hazards. The evolution of global general circulation models (GCMs), a boon for the climatic studies, which are capable to predict future climatic data based on the present datasets. This prediction helps us to plan for the significant adaptation actions for safe future. Though, it is unmanageable to use the raw data of GCMs at a local scale, due to its coarse resolution. Therefore, the main aims of the present study are to estimate the effect of climate change on rainfall pattern in 3 Coastal districts of Andhra Pradesh, India, under three Representative Concentration Pathways (RCPs) from Global Climate Model data of CanESM2. The estimation was done using the Statistical Downscaling Model (SDSM) in the study area. The goal behind using this model is evaluating the efficiency of SDSM to predict the future rainfall. The actual data of three districts, (namely Krishna, Guntur and Prakasam) which finally converted into 3 weather stations using Thiessen Polygon method. The method was used for a period of 51 years (1961 - 2012) and Global Climate Model data of CanESM2 under RCPs of RCP2.6, RCP4.5, and RCP8.5 for the period of 2006-2100. The period of 1961-1995 was used as the calibration period and 1996-2005 as validation. After the validation, rainfall was recorded individually for all the three scenarios of RCPs namely RCP2.6, RCP4.5, and RCP8.5. The results showed the values of R2 and RMSE for themodel calibration and validation ranged from 0.69 to 0.86 and between 1.99 and 3.88, respectively for all three stations used in the study. The obtained future rainfall data from 2020-2100 was then correlated with the base period rainfall from 1961-1995. The trend shows that the overall volume of precipitation will increase in this region (three districts of Andhra Pradesh) of lower Krishna River for the period of 2020-2100 as compared to the base period due to the change in climate. The approximate predicted change up to the 21st century will be 19.51%, 18.50%, and 15.99% for Guntur, Krishna, and Prakasam districts respectively under the worst scenarios of RCP8.5. Therefore, it is concluded that the future pattern of rainfall in these three districts of Coastal Andhra Pradesh, under RCP4.5 and RCP8.5 constantly increasing, especially in the case of RCP8.5 due to the climate change.