GEOWEPP MODEL APPLICATION IN SIMULATING SOIL EROSION IN BAMBOO PLANTED AND CULTIVATED CATCHMENTS

摘要

This study applied the Geospatial Interface for Water Erosion Prediction Project (GeoWEPP) to determine soil erosion and sediment yield in the two catchments with and without bamboo, respectively. The catchments are located within Taganibong Watershed in Bukidnon, Philippines. GeoWEPP simulation requires four main input files corresponding to climate, slope, land management, and soil. Climate input file was processed within the Breakpoint Climate Data Generator (BPCDG) computer program based on the 2014 climate data collected using the automatic weather station. Slope input file was generated from Digital Elevation Model (DEM) derived from Interferometric Synthetic Aperture Radar (IFSAR) data. Soil and management input files were processed from field surveys. Separate database files in text format were also created to link WEPP model with GIS tool. Plant databases for bamboo obtained from various literatures were used to adjust the parameters of plant databases within the WEPP model environment. After series of calibration, soil erosion rate was predicted at an average value of 13.52 and 56.04 th~(-1)'y~-1 for catchments with bamboo and without bamboo, respectively. The respective sediment yields of 20.90 and 104.95 th~(-1)y~(-1) for site with bamboo and without bamboo were also simulated. Results showed that catchment planted with bamboo has consistently lower erosion and sediment yield values suggesting the capability of bamboo in reducing soil erosion and sedimentation rates. Model validation using observed data for catchment with bamboo showed satisfactory performance with coefficient of determination (R~2), Root mean square errors-observations Standard deviation Ratio (RSR), Nash-Sutcliffe Efficiency (NSE) and percent bias (PBIAS) values of 0.64, 0.62, 0.61, and 44.35, respectively. For cultivated sites or area without bamboo, R~2, RSR, NSE and PBIAS values of 0.85,0.66,0.56 and 25.62, respectively, were obtained. Overall, GeoWEPP performed satisfactorily implying applicability of the model in catchments with and without bamboo planted and steeper hillslopes like Taganibong.