Using GIS and the RUSLE model to create an index of potential soil erosion at the large basin scale and discussing the implications for water planning and land management in Morocco

Severe erosion rates endanger the drinking water and agroforestry sectors in Morocco. To determine ways to improve erosion mitigation in Morocco, this study examined the political landscape underpinning research and policy implementation nation-wide. It also conducted a case study for erosion modeling in the most important river basin for drinking water in Morocco, the Bouregreg Basin. In this case study, 15 erosion scenarios were constructed in ArcMap according to the Revised Universal Soil Loss Equation (RUSLE), the most commonly used tool to predict erosion in Morocco, to determine the effect of variation in data inputs on the quantity and severity of sheet and rill erosion. Results indicate that average annual erosion rates in the Basin are minimal to moderate, with localized areas experiencing severe rates over 25 tons/hectares/year, indicating that channel and gully erosion rather than sheet or interill erosion dominate in the basin. Increased DEM resolution from 30 to 90 meters amplified predicted erosion rates by a factor of 10, and variation in precipitation between the highest and lowest agricultural years yielded a difference in maximum erosion rates of nearly 60,000 tons/hectares/year.

These results indicate that the spatial resolution of datasets and variation in climatic factors produce substantial differences in model output and may bias policy-making in light of variation in data management practices and the potential effects of climate change. In order for Morocco to reach its goal of implementing Integrated Water Resource Management (IWRM), operators and researchers should collaborate at the basin level and establish best data management practices in the drinking water and agro-forestry sectors of Morocco. To achieve these changes, this study recommends that decision makers reexamine how they fund and support erosion research and mitigation, and that all stakeholders coordinate to both compile data to develop empirical and process-based erosion models fitted to Morocco and calibrate these models through investing in representative field studies.