Development of GIUH for small catchments in Sagar district

Abstract

The geomorphological characteristics are mainly useful in rationalization of the hydrological models of rainfall runoff process, which aim at development of scientific basis for predicting the model parameters of the ungauged watersheds from hydrologic and physiographic characteristics of that watershed. For estimating the parameters of hydrologic models, either optimization technique using rainfall and runoff data or topographical and climatic information of the basin may be used. The Clark model involves routing of rainfall excess through concentrated storages, which represent the storage effect of the basin. In this model a unit rainfall excess occurs uniformly and instantaneously over the basin and the inflow to the concentrated storage at the basin outlet is proportional to the time-area diagram. The parameters of Clark model can be computed easily if adequate rainfall and runoff records are available. But for ungauged catchments, the geomorphological instantaneous unit hydrograph (GIUH) approach may be applied for the simulation of rainfall and runoff. The National Institute of Hydrology, Roorkee (India) recently developed a model in which the geomorphology of a basin can be used effectively for evaluation of parameters of Clark model. In the present study, this model has been applied in some selected watersheds. Madhya Pradesh in spite of its good natural resources is considered as economically backward state. The people of this region mainly depend on agriculture for their living. About 80 % of cultivated area is rain fed. The Govt. of Madhya Pradesh in the year 1994 constituted the Rajiv Gandhi Watershed Mission with the aim of conservation of natural resources. The soil and water were considered the most important natural resources. Near about 500 watersheds have been developed till date. In order to conserve water in these watersheds, small structures are being constructed and it is strongly felt the need of development of some methods, which require minimum data for design of these structures. In the present study, twenty small watersheds of Dhasan and Bebas basin have been selected for the analysis. The geomorphological characteristics of all these basins have been worked out using ILWIS software. The relationships between commonly used geomorphological parameters were determined. The time-area diagrams of all these basins were prepared using the capability of ILWIS. The small interval rainfall and corresponding discharge data for a few storms in four selected sites have been measured iii to develop the relationship between velocity of flow and intensity of rainfall. A FORTRAN based computer program has been developed for the GIUH based Clark model as per the methodology suggested by National Institute of Hydrology. The model has been applied on five watersheds of the region. From the study, it has been observed that the GIUH based Clark model can be used conveniently for the simulation of rainfall and runoff in the ungauged or basins with very limited records.