NIH/AR/2009-13:Impact assessment of climate change on hydrological regime in Sabari sub-basin Godavari river system

Abstract

Trend analyses of climatic variables (rainfall & temperature) were carried out for Sabari subbasin using historical period of 109 years (1901 to 2009). Mann-Kendall trend analysis was used to predict the trends of the climatic variables in the study area. The results reveals that the temperature is in increasing trend in the all the months with 95% confidence level. Whereas, rainfall has no trend in monsoon period except the September month shows decreasing trend. Linear trend analysis were also carried out, the results of linear analysis also in line with Mann-Kendall outcome. The daily rainfall-runoff modeling was carried out using ARNO model for a period of 39 years (1970 to 2008). Calibration and validation was carried out for a period of 30 years (1970 to 1999) and 9 (2000 to 2008) years respectively. The model efficiency during the calibration and validation run was 72.35% and 70.16% respectively. RCM downscaled data for base line (1960 to 1990), mid-century (2021 to 2050) and end-century (2071 to 2098) period obtained from IITM, Pune has been used in the validated ARNO model for the analysis of hydrological scenarios due to climate change in the sub-basin. The IMD and RCM downscaled data for the base line period (1960-1990) has been compared and found that there is in huge variation in both the temperature and rainfall measurements. The minimum and maximum temperature measured by the IMD was 22.3 and 38.7 oC whereas predicted by RCM was 32.5 and 48.6 oC respectively. For the above said period the average temperature measured by IMD and predicted by RCM was 32.8 and 40.2 oC respectively. The RCM downscaled data shows that the minimum, maximum and average temperature predicted during the summer season for Mid Century period is 34.7, 50.6 and 43.5oC respectively. The values for the End Century period is 35.8, 53.4 and 45.3 oC. The maximum rainfall measured by IMD and predicted by RCM for the base line period is 485.1 and 1235.47 mm respectively. Whereas for the Mid and End century period is 115.54 and 1237.25 mm respectively. The runoff predicted using the RCM data for the Mid (2021 to 2050) and End Century (2071 to 2098) periods show a frequent high peak floods like scenario.