Alih Ragam Hujan Menjadi Debit di Sub DAS Ciliwung Hulu

Abstract

Rainfall-discharge transformation in a watershed is an indicator that shows the capability of watershed to control water yield and flood. During 2007-2012, in the region of Jakarta and Bogor show that the rainfall transformation into runoff in Ciliwung watershed including upper watershed in Ciliwung remains high. Knowledge about rainfall transformation in Ciliwung upper watershed are needed. Hydrological models are possible to estimate that rainfall transformation. One of the models that currently often be used is SWAT (Soil Water Assessment Tools) model. The prediction of discharge with SWAT model in Ciliwung upper watershed has satisfying result with coefficient of determination (R2) 0.53 and NSE 0.73. Landuse changes from 2009 to 2012 has decreased the coefficient of measured runoff from 0.76 into 0.22 and based on the estimated runoff has decreased from 0.9 into 0.7. Based on the best scenario of the landuse changes is to apply soil and water conservation in agricultural land with contoured tillage and improving mixed agriculture with agroforestry system, rainfall – runoff transformation runoff decreased from 1763 mm/year into 1565.2 mm/year and the discharge decrease from 4367.0 mm/year into 4350.9 mm/year.