WATERSHED MANAGEMENT USING GIS IN EAST JAVA PROVINCE OF INDONESIA

Abstract

A watershed is made up of the natural resources in a basin, especially the water, soil and the vegetation factor. The comprehensive development of a basin so as to make productive use of all its natural resources and also protect them is term watershed management. Watershed management particularly refers to the development of land water resources. This requires a reliable information on various characteristic of a watershed such as topography, land cover, rainfall, drainage, soil, geology etc. The information normally acquired from different sources for watershed management is large in volume and needs an efficient system wich stores, handles, manipulate and analyzes this information. Geographic Information System (GIS) is a computer based system design to store, process and analyzes spatial data and their corresponding attribute information. Due to their capabilities and wide application the GISs are becoming important in natural resources management. This work present in this study is runoff potential assessment from existing watershed management and the erosion hazard level under existing and proposed condition of watershed management using Integrated Land and Water Information System (ILWIS). ILWIS is a GIS developed by International Institute for Aerospace Survey and Eart Sciences (ITC), Enschede The Netherlands. ILWIS has both raster and vector based capabilities some basic principles of GIS are also reviewed for general conceptual understanding. Jati watershed and Singgahan watershed, which locate in Trenggalek District, East Java Province Indonesia, are selected . Government of Eat Java Province through The Brantas River Basin Development has planned to construct a rain water structure, likely small dam in the outlet of two watersheds. This study is to assess runoff availability, runoff requirement for development plan and . water balance in the watersheds, however assessment of soil loss hazard with existing watershed management which will become a problem in erosion and sedimentation in the small dam, and proposed watershed management that is. soil conservation practices which will expected to reduce soil loss hazard. M Tech Dissertation iii ABTRiCT The potential runoff from watershed under current management conditions was assessed and estimated using SCS- direct runoff model based on the availability rainfall data. The model parameters are CN and S were evaluated under different management conditions. Universal Soil Loss Equation (USLE) and SCS runoff model parameter were analyzed and their attribute map were generated from the common spatial data base created by ILWIS Soil erosion due to sheet and rill form the watershed under consideration has assessed and estimated using the USLE empirical model. USLE has six factors rainfall erosivity factor (R) , Soil erodibility factor (K), topographic factor (LS), Crop Management factor (C), and conservation support (erosion control) practices (P). The values of these factors were analyze depending on the data available for different management conditions. Finally the result ( along with brief discussion) of the estimates of runoff. avaibility, water balance, and soil loss in the watershed model under existing and proposed condition are given in the form of figure and table.