Characterization and Quantification of Meteorological Drought in the Oued El-Abid Watershed, Central High Atlas, Morocco (1980-2019)

The present study is focused on analysis of rainfall in the Oued El-Abid watershed, which is characterized by an important potential in water supply of the Bin El Ouidane dam and the recharging groundwater of the plains downstream. The aim of the present research is to characterize the meteorological drought in the Oued El-Abid watershed, located in the Beni Mellal-Khenifra region (Central High Atlas, Morocco). The study focused on the analysis of the meteorological drought detection indices such as the deviation from the mean (DM), the rainfall index (RI) and the standardized precipitation index (SPI) based on annual precipitation for the three stations (Tilouguit, Ait Ouchen and Tizi N'Isli) generally experienced alternating periods of surplus and deficit. The results of these indices allowed us to determine the most remarkable and common drought years are: 1981, 1983, 1990, 1998, 2001, 2005, 2017 and 2019. This study is helpful for water resource managers to make decisions and develop tools for adaptation and mitigation of climate change impacts.

Impacts of Climate Change on the Hydro-Climatology and Performances of Bin El Ouidane Reservoir: Morocco, Africa

In arid and humid contexts, dams’ reservoirs play a crucial role in water regulation and flood control. Under the projected climate change (CC) effects, even a preoptimized management approach (MA) of a reservoir needs to be assessed in this projected climate. This chapter aims to assess the impacts of CC on the Hydroclimatic (HC) variables of the basin upstream the reservoir of Bin El Ouidane (Morocco), and the effects on the performances of its preoptimized MA. The applied Top-Down assessment procedure included CORDEX climate projections, hydrological, siltation, evaporation, and management models. Concerning the HC variables, the results obtained concord with those reported in the literature in terms of trend, but not always in terms of intensity of change. On the other hand, the projections expected a decrease in the performances of the reservoir, except for criterion allocations’ standard deviation, calibrated during the optimization. Also, interesting conclusions have been found like: the change in precipitation dominant form, the accentuation of the pluvial hydrological regime, the advanced snow melting due to the temperature increase. This chapter presents a typical case study on how to use climate projections for reservoir MA adaptation, without being highly and negatively influenced by the climate model uncertainties.

MODELLING RESERVOIR SEDIMENTATION AT BIN EL OUIDANE DAM, MOROCCO

This study was conducted in the Oued El Abid watershed upstream of the Bin ElOuidane dam, in Tadla-Azilal province (Morocco) to quantify the dam siltationrates. To assess the annual soil erosion and the sediment yield the universal soilloss equation (USLE) was used. A geographic information system (GIS) was usedto generate and integrate maps of the USLE factors. A spatial distribution of soilerosion in the Oued El Abid watershed was obtained. The soil erosion wasdetermined for each rural commune in order to identify the soil erosion hotspot andestimate the amount of soil that has been transported downstream (Bin El OuidaneDam). Soil erosion ranged from very limited values for flat and well covered areasto over 2100 t /ha/y in mountainous areas with sparse vegetation. The total annualsoil loss within the watershed is estimated at 19. 6 million tons per year. Anequation of sediment delivery ratio (SDR) based on river gradient was calculated.It was found that the value of SDR at the outlet of the watershed Oued El Abid was0. 65 with a sediment yield of 12. 74 million tons per year which affect thedurability of the dam.