STUDY OF FOREST COVER AND ITS IMPACT ON WATERSHED MANAGEMENT IN YAMUNA SUB-BASIN

Abstract

The science of hydrology is concerned with the movement and distribution of water throughout the various phases of the hydrologic cycle. Watershed management uses • the knowledge of hydrology to control floods, prevent erosion, increase the yield of water from the watershed, and thereby provide an adequate supply of water for agricultural, commercial and industrial purposes around to the source of supply. These purposes are served by managing the vegetation cover and land use in. the watershed and building various structures to control the flow and storage of water. The choice of management practiceS to be used in a watershed should be based on information about the hydrologic cycle of that watershed. Remote sensing techniques seek to recognize and classify objects and their conditions through their characteristics electromagnetic signatures. It can best help in identifying the land surface cover and can be used to infer the hydrologic features like runoff potential, infiltration, evapotranspiration, soil loss etc. In the present study various land use maps pertaining to different periods have been prepared by visual interpretation of Landsat imageries. Also relevant information have been collected for geology, soil, geomorphology and drainage pattern. The Yamuna Sub-basin lies between Longitudes 77°57'13" to 78°11'56" East and Latitudes 29°18'57" to 30051'55" North. The Yamuna river criginatet in Tehri-Garhwal district of Uttar Pradesh from the Yamnotri glacier on the south-western slope of Banderpunch glacier at an elevation of 6320 meters. The area is covered by Landsat imagery scene no. of 157-039. The forest cover study of Yamuna Sub-basin has been done with the watershed management point of view. The various categories of land use/land cover recognized in the area by visual interpretation of Landsat imageries are as follows: 1. Dense forest 2. Moderate forest 3. Thin forest 4. Sparse vegetation 5. Cultivation/grassy 6. Barren land 7. Bare rock R. Snow For assigning an effective watershed management program, the catchment has been divided into 12 watersheds , and change in areal extent of land use/vegetal cover categories has been determined in each of the 12 watersheds. Stream order, bifurcation ratios, topographic factor and other geomorphological parameters have been computed from the drainage maps for the 12 watersheds prepared from the FCC at 1:250,000 scale The hydrological losses such as interception, evapotranspiration and infiltration have been evaluated for the whole catchment. Then the computed runoff values have been compared with the observed flow values at the Lakhwar dam site. An estimation of soil loss for each of the watershed has also been made within a short temporal span of 10 years which has indicated that the Khutna Gad watershed is susceptible to most severe erosion, and soil conservation is the only effective answer for the severe soil problem in that watershed.