Modelling the effect of conservation measures on potential soil erosion: a USLE and GIS approach

Quantitative assessment of soil loss in Ambika watershed, Gujarat, India was done using universal soil loss equation (USLE) and geographic information system (GIS) to analyse spatial distribution of soil loss. The annual average soil loss for the entire watershed was estimated at 22.41 tonne ha(-1) year(-1), which substantially contributes to low agricultural productivity of the area. About 80% of the watershed area is affected by moderately high to very high soil erosion (>15 tonne ha(-1) year(-1)) and requires immediate attention for soil conservation measures. The average slope of micro-watersheds in this area varies between 5% and 8%. So, according to recommendations of land capability classification for class IV lands, contour bunds and terraces were selected as soil conservation measures, which resulted in the reduction of annual average soil erosion of the entire watershed to 17 tonne ha(-1) year(-1). Therefore, these conservation measures can be effectively applied in watersheds with similar geomorphology and average slope up to 8%, to reduce soil erosion. The cumulative effect of soil conservation measures indicated that area affected by soil erosion magnitude under priority class 1 was reduced from 7.5% to 0%; under priority class 2 it reduced from 49.75% to 37.19%, and for priority class 3 the area reduced from 22.41% to 17.63%. Hence, determination and monitoring of soil erosion and subsequent planning of soil conservation practices for improving agricultural productivity can be effectively achieved using USLE and GIS technology.