Length of Series for Estimation of Runoff in A Major River

Abstract

The length of series required to be considered for estimation of yield and dependable yields is a very important issue. Any length of period having more number of good years may result in over estimation of yield and vice versa. The IS code suggest a minimum period of 40 years for estimation of yield at a project site. It also suggest that if the data is not available for 40 years then rain fall runoff regression techniques be used to increase the length to the minimum required length of 40 years. The CWC also suggest a length of 40 years. This length may be sufficient for a project site but more length may be required for correct estimation of yield in a river basin. Many hydrologists are of the opinion that more the length more accurate will the estimation of yield . This paper attempts to derive the minimum length required for estimation of yield in a major river like Krishna river considering the data from 1894-95 to 2007-08 using statistical analysis. A period of about 92 years may be required for correct estimation of yield in the Krishna river.