Hyetograph - hydrograph transformation model for uniform and non-uniform rainfall distribution patterns

Abstract

Techniques used for determination of runoff hydrograph require historical recorded runoff data and other complex information for evaluating various parameters, which are generally not available in case of un-gauged watersheds. Therefore, an attempt has been made to develop a model which is capable of transforming available rainfall hyetograph in to direct runoff hydrograph by using information about land use pattern and other topographical features of the study area. In the development of models, the storm runoff has been estimated by using SCS curve number method. The model formulation was attempted considering uniform and non uniform rainfall distribution patterns. In case of uniform rainfall distribution, the model was formulated on the basis of one step rainfall input and accordingly named as one step rainfall input (OSRI) model. While in case of non uniform rainfall distribution, the entire storm duration was divided into smaller constant rainfall intensity increments and the model was formulated considering multiple step rainfall input and called as multiple step rainfall input (MSRI) model. It was observed that MSRI model provided better estimation of runoff hydrograph as compared to OSRI model. Estimated peak rate of runoff and time to peak values have a very good correlation (0.97) with the observed values and the coefficient of efficiency between them is 97.19%.