SOIL EROSION MODELLING OF A HILLY CATCHMENT

Abstract

This study attempts to estimate the average annual soil loss from the Nathpa Jhakri catchment employing the well-known Universal Soil Loss Equation (USLE) and Morgan-Morgan-Finney (MMF) models. The rainfall erosivity factor for USLE model was estimated using the Arnoldus equation based on the monthly rainfall data of years 1971 to 1996. Some of the model parameters were obtained using satellite data. Geographic Information System (GIS) was used as a tool to generate, manipulate and spatially organize disparate data for soil erosion modelling. The average annual soil loss using the USLE and MMF models were 20.42 tons/ha/yr and 26.29 tons/ha/yr respectively. The coefficient of determination of the USLE sediment results was (R²=0.8029) with a variation of (13.41%), and the coefficient of determination for MMF sediment results was (R²=0.7457) with a variation of (21.62%). The total catchment area was categorized into the following erosion classes: slight (0 to 5 t/ha/yr); moderate (5 to 10 t/ha/yr); high (10 to 20 t/ha/yr); very high (20 to 40 t/ha/yr); severe (40 to 80 t/ha/yr); and very severe (>80 t/ha/yr). The USLE model shows that 35.8% of the Nathpa Jhakri catchment area lies in the slight to moderate soil erosion classes and 64.2% lies in the high to very severe soil erosion classes. The MMF model shows that 13.88% of the Nathpa Jhakri catchment area lies in the slight to moderate soil erosion classes and 86.12% lies in the high to very severe soil erosion classes. The study revealed that the USLE model shows more precise results of soil erosion than the MMF model results for the Nathpa Jhakri catchment. Approximately 64.2% of the Nathpa Jhakri catchment area needs immediate attention from soil conservation viewpoint.