CS(AR)-27/97-98 : Regional low flow analysis for Narmada basin

Abstract

The term low flow is broadly used to describe stream flows that are significantly below average or below normal flow levels. Reliable estimation of low stream flows is necessary to investigate drought characteristics of the basin and to describe the capability of a stream to supply requirements for river navigation, municipal and for industrial supplies, liquid water disposal, irrigation and maintenance of suitable conditions for aquatic life. The important characteristics in the study of low stream flow are the magnitude, frequency and duration. Regional models are developed relating the flow characteristics with climatological, hydrogeological and morphological factor for estimation of low flow characteristics for ungauged sites.

In the report a regional hydrological model is developed for estimating flow characteristics at ungauged sites of Narmada basin using climatological, hydrological and morphological variables. The model is developed by relating the low flow characteristics with other variables of nine sub basins of Narmada. Correlation analysis suggested that the variables like drainage area, slope of maximum stream length and percentage clay in soil could be the prime independent variable which could be related to the flow characteristics. Normal monsoon and non monsoon rainfall did not show the correlation with ten day flow duration characteristics. Mean annual minimum flow characteristics of flow indicated the correlation with base flow index and the rainfall of December month. Factor analysis indicated the highest ranking of the independent variables in the model are drainage area followed by slope of maximum stream length and percentage clay in soil. The model showed the adjusted coefficient of determination greater than 0. 95. The mean annual minimum flow model indicated the highest ranking of base flow index followed by rainfall of December month. The models explains the adjusted coefficient of determination greater than 0. 91. The verification results of both the flow characteristics are also presented.