Water Erosion in the Moulouya Watershed and its Impact on Dams' Siltation (Eastern Morocco)

Abdelkader Sbai,Khadija Benrbia,Abdelouahid Saidi,Mostafa Bouabdallah,Omar Mouadili,Fatima Zahra Mazari,Mohamed Hlal

doi:10.5194/piahs-384-127-2021

Abstract

Abstract. The Moulouya watershed presents high risks of water erosion. The dams built on this river lose each year, by siltation, a volume of water of about 10 M m3 (Lahlou, 1994). This worrying rate shows that water erosion can hinder the socio-economic development of the basin if soil protection and siltation measures are not taken. This study defines the areas most threatened by water erosion to protect them as a priority. Using a GIS and the Universal Earth Loss Equation (USLE), we mapped soil losses. The adopted model determines soil loss from erosivity of rainfall, soil erodibility, inclination and slope length, soil cover, and erosion control practices. The possible origins of the deposits alluviating the dams are related to the products of alteration of the Secondary's carbonate formations and the Tertiary and Quaternary formations. The modalities of the transport of deposits of banks of the network of Moulouya are mainly by a suspension. The specific degradation in the Moulouya watershed is estimated at 214 t/km2/year. Precipitation intensity, steep slopes and deforestation are responsible for these losses.

Highlights

The degradation of natural resources by water erosion is one of the worrying risks that threaten human stability and is difficult to reduce
The forms of current dynamics in the Moulouya basin are dominated by water erosion
After calculating the various factors adopted in the universal soil loss equation, we calculated the areas of eroded land (Fig. 2)

Summary

Introduction

The degradation of natural resources by water erosion is one of the worrying risks that threaten human stability and is difficult to reduce. It has been greatly exacerbated in recent years by the threat of the current dynamics, which could directly threaten food security and the population’s health. It has led to the emergence of problems that can only be alleviated by integrated measures ensuring decent life for the population and preserving natural resources and sustainability for future generations. It presents a high risk and causes siltation of dams and significant losses of water volumes. This erosion is governed by the nature of the fragile geological formations, especially the superficial quaternary formations, the nature of the sandy loam soil, the steep degree of the slopes, the slopes’ dry exposure, and the type of land use (cultivation and overgrazing)

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Conclusion