Remote Sensing and GIS Applications for Estimation of Runoff in an Ungauged Watershed

Abstract

The basic concept of Integrated Water Resources Management (IWRM) is to integrate not only the stakeholders but also various sources of supply is put together to fulfil the demands. Precipitation is the main source of water in the river basins, which is not uniform over space and time. The surface water management requires the storage structures to be created on the rivers and rivulets at surplus locations during surplus periods. Knowledge of availability of total water and peak flow are the major design criteria of any water resource structure. Estimation of peak flow and total volume of water becomes a difficult task for the ungauged catchments. For the purpose of computation of peak flow and total runoff estimation, an attempt has been made to compute the total volumetric runoff through the water balance of Bina river watershed using the Thornthwaite and Mather model. Also, the SCS-CN method developed by soil conservation services (SCS) has been adopted for accomplishment of the above stated objective. The input parameters to the SCS-CN model and Water Balance model, i.e. landuse, soil texture, and hydro-meteorological data have been computed with the help of remote sensing and GIS techniques. Three years rainfall and runoff data from the year 2006 to 2008 have been used for evaluation of the model performance. The model efficiency has been checked with the observed runoff data available for Bina river watershed for short duration. The runoff computed by SCS-CN model has been found more accurate than those of the runoff estimated by the Thornthwaite and Mather model. Both the methods provide volumetric runoff, however the SCS-CN can be utilised to compute peak discharge by convolution of the estimated rainfall excess with SCS Unit Hydrograph (SCS-UH) of the desired watershed.