Soil Loss Prediction Using Revised Universal Soil Loss Equation (RUSLE) for Amochhu Watershed in South-western Bhutan

Tsheten Dorji, Tashi Wangdi, Dawa Tashi, Karma Dema Dorji & Yeshey Chedup

ABSTRACT

Soil erosion by water is a serious problem all over the world affecting sustainability of agricultural production. In Bhutan, the limited productive land suffers risk from various forms of soil erosion. Although the soil erosion is common in all parts of Bhutan, it is not well quantified and documented. To generate information on soil loss, this study was conducted in Amochhu watershed using Revised Universal Soil Loss Equation (RUSLE). Geographic Information System (GIS) was exclusively used to generate factor maps of RUSLE. The factor maps include rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), Cover management (C), and conservation practice (P). A spatial distribution of soil erosion over Amochhu watershed was obtained by integrating all the factor maps in Arc GIS environment. The soil erosion was found to vary between 5 Mt/ha/yr for well covered areas (forest) to more than 150 Mt/ha/yr in steep-slope areas with sparse vegetation. The average soil erosion is 130 Mt/ha/yr. The predicted amount of soil loss and its spatial distribution provides a strong basis for integrated management and sustainable land use for the watershed. It also gives clear picture as to where we need to focus our sustainable land management interventions. However, similar soil loss prediction study needs to be rolled out to other watersheds so that we have soil loss information at the national level.

Keywords: Soil loss prediction, RUSLE, GIS, Amochhu Watershed, Bhutan

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