CS(AR)-11/98-99 : Implementation of SCS modelling in Dudhnai sub-basin (Assam/Meghalaya)

Abstract

In a predominantly agrarian country like India water is the most vital but limited natural resource for the survival of mankind. Therefore it has become necessary to estimate the amount of water that flows as runoff on the surface of the earth to be obtained from rainfall. To calculate the amount of runoff rainfall is an essential input. In many regions of the country rainfall records are available for fairly long period but runoff records are inadequate in most of the cases particularly on sub watershed level. Therefore runoff estimation using a suitable model that transforms the available rainfall into runoff forms an essential task in hydrological analysis.

Runoff depends on a multitude of climatic and physical characteristics such as landuse soil and moisture. For converting rainfall to runoff the model which incorporates these three important watershed characteristics is USDA (United States Department of Agriculture) Soil Conservation Service (SCS) method. Hence SCS method is chosen to estimate daily runoff in the present study.

The important constituents of the SCS model viz. landuse/landcover can be accurately delineated using remote sensing with the advent of its features of synoptic view repetitive coverage and reliability. Hydrological Soil condition representing the runoff potential of a particular soil is derived from the soil atlases available with the Soil Survey Organisation of the region. Antecedent moisture condition that alters the runoff volume has been taken account for in this study.

In this study the representative Dudhnai basin has been selected for implementing the model. Runoff volume has been estimated for all the nine subwatersheds of the study area. Four subwatersheds has been selected for water conservation measures.