Frequency Analysis of Rainfall & Discharge for a Sub-Watershed of Cauvery River

Abstract

Abstract The analysis of precipitation data would upgrade the management and effective utilization of water resources, which thus anticipates flood and dry season. Precipitation and temperature data from 1901 to 2016 were extracted from the CRU TS 4.01 data set for the grid enclosing the sub-watershed of the Cauvery river. Basic statistical analyses were conducted on this data to learn about the long-term characteristics of the rainfall. From the analysis of rainfall characteristics, it has been observed that NEM and SWM contribute and accounts for 83.4% of the total annual rainfall. Using Weibull (1951) method, the estimation of probability of exceedance was carried out through rainfall frequency analysis and 50%, 75% and 90% dependable rainfall values were found to be 894.40 mm, 801.10 mm and 683.30 mm, respectively. The Departure analysis of rainfall was also conducted and the result showed that 72% of the total years (116 years) were observed under normal rainfall. For the analysis of rainfall, the CARTODEM tiles corresponding to the location were downloaded from Bhuvan website and the watershed boundary map was generated in ArcMap 10.1. An empirical equation was used to estimate the discharges corresponding to the rainfall period and the annual average discharge for the watershed was calculated as 63.88 cumecs. The flow duration curves within the watershed were developed and plotted through the estimated discharge. The 50%, 75% and 90% of probability of exceedance values were found to be 62.4, 54.4 & 44.3 cumecs, respectively for the yearly discharges.