Watershed Prioritization Based on Morphometric Analysis and Soil Loss Modeling in Wadi Kerak (Southern Jordan) Using GIS Techniques

Abstract

Wadi Kerak catchment, located in southern Jordan, covers an area of 191 km². It is characterized by high soil erosion rates due to recurrent intense rainfall events and possibly climatic change, land use/land cover changes since the 1950s, and the dependence of people across the watershed upon rainfed and irrigated farming. The aim of this research is to determine soil conservation prioritization for thirty one third-order mini-watersheds (MW1-MW31) based on morphometric analysis and soil loss modeling methods. Linear and shape morphometric  parameters have been computed for each mini-watershed on the basis of their value/relationship with erodibility, and rank is assigned in order to obtain compound values for final ranking of the mini-watersheds . Soil loss rates also have been estimated using the RULSE model. RULSE factors (R, K, L, S, C, and P) were calculated in a GIS environment, then multiplied together so as to compile soil loss maps/tables, and to estimate soil loss(ton  ha-1 year-1)for the thirty one mini-watersheds. Based on morphometic parameters and soil loss values, and their rankings, the mini-watersheds have been grouped into five classes: extremely high, very high, high, moderate, and low with reference to their priority for conservation practices and watershed management. Two maps were generated separately and illustrate the prioritization of the mini-watersheds based on morphometric analysis and soil loss modeling. Then an integration of the two maps was conducted to recognize the common mini-watersheds falling under each category of priority. It can be demonstrated that 50% of the mini-watersheds can be grouped under moderate, high, very high and extremely high priority based on both soil loss modeling method and morphometric analysis. Consequently, a considerable number of the mini-watersheds should be prioritized for implementing soil and water conservation measures to ensure future sustainable agriculture.