Interpolation of short duration rainfall from 24-hou r rainfall in lower Godavari basin

Abstract

Short duration rainfall estimates for different return periods ore required in many problems concerning flood estimation for design purposes. A general paucity of data in the form of inadequate network of self recording raingauges (SRRG) and also the inadequacy of available period of records often necessitated the water resource planners to develop alternate techniques to overcome this deficiency. An attempt has been made in this paper to estimate short duration extreme rainfall for a given return periods from a knowledge of 24-hour data of ordinary non-recording raingauges. The procedure adopted in the study is as follows :

Using data of randomly selected 14 SRRGs out of already existing network of 17 S.R. raingauges in lower Godavari basin regression equation was fitted between a short duration rainfall estimate and 24-hr rainfall estimate for a given return period. The coefficients of regression curve were worked out by the least squares method with basin as a unit.

Using these constants and coefficients, estimates of short duration in a problem area were made. The short duration rainfall estimates for 2 and 50-year return periods were computed for three existing SRRG stations which were not used in the computation of regression coefficients and four ordinary raingauge stations in and around the sub-zone. The errors, on comparison are found to be within reasonable limits. The technique presented in the paper can be employed to estimate short duration rainfall, from daily rainfall records for any area.