Soil erosion estimation for the sustainable planning of a Semi-Arid Micro-Watershed in Southern Telangana

Abstract

A spatial soil loss estimation model was developed for estimating the soil loss from Padmaram micro-watershed in Mahabubnagar District of Telangana State using GIS coupled with Revised Universal Soil Loss Equation (RUSLE). Different thematic layers of rainfall, soil, land use land cover, flow accumulation and slope were intersected using ARCGIS software and RUSLE was applied for estimating the soil loss from this ungauged micro-watershed. The daily erosivity was estimated for 57 years using Aphrodite rainfall data and the slope length factor (LS) factor was determined spatially. The cover and management factor (C) and conservation practice factor (P) values were selected based on the crops grown and the conservation practices. The mean annual soil loss for the period 1951 to 2007 was below 3.3 t/ha/y from 87.5% of the micro-watershed area including all the land use land covers. The mean annual soil loss estimated from crop land with and without bunding was 2.0 and 3.2 t/ha/y. Among the three predominant land use land cover, the mean annual soil loss was slightly higher for fallow land (3.6 t/ha/y) followed by scrub land (2.3 t/ha/y) and crop lands (2.0 t/ha/y). The mean annual soil loss estimated from crop land in the upstream, midstream and downstream of the micro-watershed was 2.3, 2.6 and 2.2 t/ha/y, respectively. The soil loss from crop land during drought, normal and above normal years was estimated and it has decreased in recent years. The soil loss was estimated for the changing climate scenarios using PRECIS data. The soil loss from crop land during the base line period (1961–1990) was estimated at 3.2 t/ha/y. It is predicted to increase during mid-century to 4.0 t/ha/y and decline during end century to 3.0 t/ha/y. In Padmaram watershed, considerable temporal variation in soil loss across the years was not observed. Soil erosion associated with agricultural practices in semi-arid tropics, leads to decline in soil fertility and also results in many environmental problems, and hence its quantification is the need of the hour for planning interventions for controlling erosion for the sustainable agricultural production and water quality.