Gajahwong River Continuous Flow Simulation by Using Soil Moisture Accounting (SMA) of HEC HMS

Abstract

Gajahwong River is located in the southern part of Java Island, Indonesia, specifically on Daerah Istimewa Yogyakarta. Gajahwong River has an important role along the area where its discharge is used especially for irrigation water supply. Other factors stressing Gajahwong basin’s water supply purpose are population number rise and land cover change that influence river streamflow in the whole year. Hence, a continuous flow simulation was conducted to analyze Gajahwong River water availability to supply its requirement. The Soil Moisture Accounting (SMA) module of HEC-HMS was employed to simulate the continuous flow of Gajahwong River, particularly in Wonokromo Outlet. The continuous flow was simulated from the year 2012 until 2015 based on observed discharge data availability. Comparison between simulated and observed discharge was quantified by using R2, Nash-Sutcliffe efficiency and PBIAS statistic value. The statistic above parameter values yielded a value of 0.90, 0.58, and 2.02%, respectively for daily time series simulation.