The Effect of Land Use Changes on the Water Balance in the Ciliwung-Cisadane Catchment, West Java, Indonesia

摘要

[ABSTRACT] The purpose of this study is to clarify the effect of land use changes on the water balance in humid tropics catchment area. The Ciliwung-Cisadane watershed of West Java, Indonesia, is selected as study area where intensive land use changes have occurred in the recent past. The elements of water balance such as precipitation, runoff and evapotranspiration into and from the catchment were estimated independently with data obtained from direct measurement or model calculation. Based on the observation data, there was an increase in runoff ratio of Ciliwung River and Cisadane River about 5-0x1.fc1bp+0nd 4% respectively. It indicates that there are some natural or artificial changes of land use that disturb the riveru27s flows and other water cycle components such as evapotranspiration. Satellite remote sensing data of 1984 and 1991 are used to reveal the land use changes. As results, there recognized large amount of change from paddy to cropland allocation and new settlement areas have been developed on paddy and cropland area respectively. Characteristic values of albedo are assigned to land use classes, and areal evapotranspiration of two periods are calculated by using Penman (1948) equation. As results, the amount of evapotranspiration in 1984 and in 1991 were 1,123mm and 1,010mm respectively, which decreased in the amount of 113mm (10%). According to calculation of water balance, the large amount of residue, which is termed as loss, has been found. These values indicate the possibility of the existence of percolation into deeper layers and the change in water storage.