Pendugaan Aliran Permukaan Berdasarkan Karakteristik Daerah Aliran Sungai Walanae, Sulawesi Selatan

Abstract

Influence of hydrological response of surface runoff which occurred in Walanae Watershed can be known through large or small values of rainfall along river basin and the biophysical characteristics of river basin. When rainfall is small or moderate, surface runoff only occurred in region that impermeable and saturated in a river flow area / or direct falls on surface of the water. Morphometric observed in the riverbank of Walanae is the pattern river network, river order, flow drainage density, the ratio of river branching, and slope degree. Conditions of Walanae basin can be represented by calculating the coefficient of riverflow regim, which is the ratio between maximum and minimum discharges. The value of the river regim coefficients that obtained for each year respectively are; 2007 = 229; 2008 = 276; 2009 = 245; and 2010 = 340. These values indicate that the river basin Walanae has experienced degradation or malfunction of upstream watersheds, because the value of the coefficient of regim river >120 and tend to increase each year. Estimation analysis of watershed surface runoff of Walanae using method of Soil Conservation Service (SCS), is obtained by calculating the curve number of the river basin. Based on the analysis results, surface runoff capability of watershed Walanae in 2010 is higher (154.29 m3/s) than in 2005 (13.32 m3/s). This large runoff values is caused by current curve number of this large watershed. Larger value of curve number resulting larger value of surface runoff.