The study develops a regional hydrological model for estimating flow characteristics at ungauged sites of Narmada basin using climatological, hydrological and morphological variables. 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, industrial, liquid waste disposal, irrigation and maintenance of suitable conditions for aquatic life. The important characteristics in the study of low streamflow are its magnitude, frequency and duration.
Regional models have been developed relating the flow characteristics with climatological, hydrogeological and morphological factor for estimation of low flow characteristics for ungauged sites. In this study, a 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 variables, which could be related to the flow characteristics. The normal monsoon and non-monsoon rainfall did not show significant correlation with ten-day flow duration characteristics. The mean annual minimum flow characteristics indicated correlation with base flow index and the rainfall of the month of December.
The factor analysis indicated that 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 indicated an 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. The model explains the adjusted coefficient of determination greater than 0.91. The verification results of both the flow characteristics are also presented.
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