Annual flow trend analyses in the Tuntang watershed caused by Kedungsepur national strategic area development

Abstract

Tuntang watershed is one of the national priority watersheds in the Jratunseluna river basin that has a big potential for water availability. The development of a national strategic area in the Tuntang watershed causes changes in land cover in the Tuntang watershed which can result in reduced water catchment areas. The purpose of this study was to simulate the effect of land change on annual discharge trends in the Tuntang watershed and analyze the water balance projection based on land change. This study uses land cover data for the Tuntang watershed in 2019 and land cover for the Kedungsepur National Strategic Area (KSN) development plan. Daily rainfall data for 11 years from 2010 to 2020 was obtained through the Global Precipitation Measurement (GPM) satellite and validated using data from 7 rain stations located in the Tuntang watershed. Meanwhile, evapotranspiration data was obtained through the Global Land Data Assimilation System. In addition, Digital Elevation Model (DEM), flow accumulation, and direction flow data obtained through HydroSHEDS are used to provide information on the surface shape of the Tuntang watershed. Then the data that has been obtained is used as input for the simulation of the spatial hydrological model to determine the annual discharge in the Tuntang watershed using the Rainfall-runoff-inundation (RRI) model. The result of this simulation is an annual discharge for 11 years. Furthermore, a comparison is made between the flow rate of land cover map input in 2019 with land cover input for Kedungsepur KSN development. Based on the result, it is known that there has been a change in the area of the water absorption region in the development of the Kedungsepur KSN, this change has resulted in an increased extreme discharge trend and reduced annual water flow in the Tuntang watershed region.