Aplikasi Model Tangki dan Pendugaan Erosi dengan Metode MUSLE Berbasis Data SPAS di Sub DAS Sibarasok Gadang Kabupaten Padang Pariaman

Abstract

Flow distribution in a watershed is a dynamic process and very dependent on climate, precipitation and combination of land coverage, evapotranspiration rate, soil type and topography of the watershed. Hydrologic biophysic process in a watershed is a natural process as a part of the hydrologic cycle. Change of watershed hydrological condition can result disaster such as floods and landslides. Application tank model is a hydrological model that used to predict river flow characteristic by using data from the SPAS. The research located at Sibarasok Gadang Sub watershed, IV Koto Aur Malintang Sub-District, Padang Pariaman District, West Sumatra. Data was processed at the Laboratory of Forest Hydrology and Watershed, Department of Forest Management, Faculty of Forestry, Bogor Agricultural University. This study aims to examine the distribution of water flow horizontally and vertically using a Tank Model and examine rate of sedimentation in the Sub-watershed Sibarasok Gadang used MUSLE method. Stages of research include analysis of the relationship river flow and water level, processing of rainfall data, river flow, and daily evapotranspiration, and analysis of sediment and erosion rate. Total rainfall during the research is 1,575.6 mm. The results equation between Water Level and Discharge in SPAS Sibarasok Gadang was Q = 7.724 TMA 1,585 with R² = 0.968, correlation between discharge and sediment rate was Qs = 0.525 Q , with R2 = 0.971. Correlation between sediment rate observation and sediment rate MUSLE model showed a high correlation with regression equation was QsMUSLE = 4,287 QsObservasi + 0,005 with R2 = 0.788. This proves MUSLE models can be used to predict the sediment rate reasonably well. Tank Model optimization results obtained parameter values R2 = 0,816. Total flow horizontally into the river dominated by base flow of 679.861 mm with a percentage of 73.10%, followed by the intermediate flow of 16.08%, 7.21% of surface flow and sub-base flow with the smallest percentage of 3.61%. It means the capacity of infiltration is high. Water level shows the flow vertically with the highest water level in tank D (base flow) of 1378.095 mm, followed by tank B intermediate flow (47.979 mm), C sub-base tank flow (18.097 mm), tank A surfaceflow (1.456 mm). This situation shows the condition of the Sibarasok Gadang Sub Watershed is still good.