Assessing Long-Term Climate Trends of Bharathapuzha Basin, Kerala, India

Abstract

Hydrologic models are widely used as important tools in climate change impact studies. For operationalising the hydrologic models need proper bias correction in the climate data. This study aims at finding out the best suitable climate model by comparing downscaled re-analysis data on precipitation and temperature from five regional climate models (RCM’s) derived from different Global Climate Models (GCM’s) with observed data of Bharathapuzha river basin, Kerala, on the basis of the four statistical parameters (standard deviation, correlation coefficient, coefficient of variation and centered root mean square difference). The GFDL-CM3 RCM compared better with the observed data and hence, was used for further data analysis. Bias in precipitation was corrected using power transformation which corrects the mean and coefficient of variation (CV) of the observations. Since temperature is approximately normally distributed, it was corrected by fitting it to the mean and standard deviation of the observations. Comparison of the post-processed climate data to observed climate data was carried out. It is predicted that there may be a decrease of 4% to 7% in average annual rainfall during 2041-70 compared to the present day average values, whereas the decrease may be up to 10% to 15% during 2071-99. Based on the results obtained, the annual maximum and minimum temperatures are expected to increase in the future. The results obtained can be utilised in formulating future water resources management plans and for assessing the impact of climate change in the area using hydrologic models.