Simulation of Best Management Practices Using SWAT Model To Reduce Surface Runoff in Upper Ciliwung Watershed

Abstract

Serious problems encountered in watershed management are related to the vegetated-land conversion and increasing areas of critical lands. The later is caused by inproper land management ignoring land capability and suitability, lack of application soil and water conservation techniques and landuse changes. Measurement of various field parameters at watershed scale was not easy to do because of its complex characteristics which sometime interrelated to each others. Modelling can be useful to understand processes involving those parameters in a watershed. SWAT (Soil and Water Assessment Tool) is a physically-based model developed to predict the impacts of land management practices on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land uses and management conditions over long periods of time. The objectives of this research were: (1) To analysis application of SWAT model to predict surface runoff, erosion and nutrient loss (nitrate) in upper Ciliwung Hulu watershed, (2) To predict Best Management Practices in agriculture field in order to reduce surface runoff in upper Ciliwung Hulu watershed. Methods applied includes collection of primary and secondary data, preparation and analysis of the input data, application of the SWAT model, analysis of the calibration parameters, determination of the validation values and simulation land management. The research was held in the period of June 2011 until June 2012. Based on daily flow discharge in February and March 2008 and 2009, the calibration result showed an R value of 0,80 and NSE value of 0,55. Validation result in February and March 2009 and 2011 showed an R value of 0,88 and NSE value of 0,74. These results described that SWAT model can be used to predict hydrological processes in upper Ciliwung Hulu watershed. Calibration of sediment observation and nitrat data were not successful because the values between observation and simulation were so different. This condition made erosion prediction and nutrient loss prediction could not be proceeded. Best Management Practices recommended terraces to be applied in upper Ciliwung Hulu watershed as terrace is the most effective soil conservation techniques to reduce surface runoff.