Judul: Analysis of water availability, sedimentation, and organic carbon using SWAT model in the upper jeneberang watershed, South Sulawesi
Abstrak: Management of upstream watersheds is a key to get a sustainable availability of water. Moreover, failure in land managing will cause erosion which increase sedimentation in water bodies. Because of soil erosion the remnants of decaying plants on topsoil also were eroded. This case will cause carbon losses in the eroded land, which flowed into the water. Growth of population which have a tendence to increase with the time, caused increasing demand of land included in the upstream of watershed. Increased demand for land is directly proportional to the land use change and will affect watershed hydrologic condition. In the rainy season the water are not well absorbed by the land and resulted water runoff that are not utilized and caused environmental damage such as erosion and sedimentation. Sedimentation will affect the lifetime of water storage structures such as dams. With the growing volume of sediment, reservoir load will be heavier and reservoir capacity will decreased. Land use change influenced hydrological processes and also concentration of organic carbon. Objectives of the study were 1) to identify parameter-parameter of SWAT model for analyzing discharge and sediment, 2) to analyze fluctuation of discharge, sediment, and organic carbon content in sediment, and 3) to study impact of soil conservation technology applied into model. The SWAT model was applied to evaluate catchment hydrology and sediment and associated organic carbon yield using historical flow and meteorological data in the upstream of Jeneberang watershed. Sediment retrieval is done using a simple tool Experimental Sediment Trap (EST). Organic carbon content was analyzed from trapped sediment using Walkley-Black metod. The spatially distributed data (GIS input) needed for ArcSWAT interface include the Digital Elevation Map (DEM), soil data and landuse data. Meteorological data and river discharge were also used for prediction of streamflow and calibration purposes. In this study, Digital elevation map (DEM) with a resolution of 30 m × 30 m was received from ASTERGDEM. Meteorological data included daily precipitation from two rainfall stations were obtained from BPDAS Jeneberang. Soil texture, available water content, hydraulic conductivity, bulk density and organic carbon content for different layers of each soil type were obtained mainly from soil map (BPDAS Pompengan-Walane) with the scale of 1:300000 and UNESCO/FAO soil database. Landuse data was obtained from BPDAS Pompengan-Jeneberang and Soil Testing Laboratory. The upstream of Jeneberang watershed, located in South Sulawesi, Indonesia, is hilly agricultural area of 236 km2 with dominant rice field (30%), forest (25%), moor (23%), and coppice (21%). The downstream, approximately 9 km, is Bili-Bili multipurpose dam and reservoir. Type of soil is dominated by Eutric Cambisols (55%), Dystric Nitosols (29%), Humic Andosol (16%). Slope range dominant is greater than 30%. The climatic conditions are monsoonal with v annual precipitation of 2500-4800 mm/years. The dry period runs from July to September (precipitation < 60 mm/day) and the wet period from October to June (precipitation > 100 mm/day). The calibration was carried out daily using flow data from January to December 2001. Calibration process was done by adjusting 26 parameters using Algoritma SUFI2 and had identified 19 sensitives parameters. Simulated daily discharge matched
Keyword: discharge, Jeneberang Watershed, organic carbon, sediment, SWAT model