9. Low Flow in the Oued El Abid Basin (Morocco): Better Understand It to Better Manage It (Oum Errbia Basin—Morocco)

In a context where the pressures exerted on aquatic environments and the water needs of populations continue to increase, to which are added the impacts of global changes, knowledge of low water flows is a major issue. Low flow is defined as a natural, seasonal phenomenon, generally resulting from a more or less long and more or less severe rain deficit, likely to vary in time and space and leading to a decrease in flow in the streams. The Oued El Abid watershed (BVOA) is a sub-basin of the Oum Er Rbia wadi (30,600 km²). The Oued El Abid is the most important tributary of the Oum Er Rbia, with an average annual flow of 32 m³/s. A maximum average flow rate of 77 m³/s. A minimum average flow of 10 m³/s (Regional Atlas region Tadla Azilal Morocco, 2015). The regime of this watercourse alternates between brutal floods and low flow supported by water from the karst hydrosystems of the central High Atlas. The objective of this study is to characterize the low water flow rates of the Oued El Abid (Upstream) watershed with a view to better management of the water resources of this basin. The methodology used consists of extracting the VCNs (MAM) from the values extracted annually, according to a fixed period “d”, these are moving averages, calculated from the average daily flows over several consecutive days.

Monthly flow data from a single hydrometric station in our study area (Tizi Nisly) was used and covers the period from 1976 to 2018.