Drought and water mobilization in semi-arid zone: The example of Hammam Boughrara dam (North-West of Algeria)

The dam of Hammam Boughrara is an embankment dam built in a transboundary basin, between Algeria and Morocco; it was type-approved and delivered in 1998. This dam was supposed to solve the lack of drinking water in Oran (Algeria's second largest city) and enhance the agricultural perimeter of the area. It should regulate an annual water volume of 59 million m3. However, the northwest Algeria has experienced a fairly severe drought since the 80s. This article aims to show the impact of this drought on the amount of surface water that can be mobilized by this dam. The rainfall series recorded at four stations, located within the basin of the dam, were examined using the proportional deviation from the average, the running average, the frequency analysis, the Pita’s index and the standardized precipitation index. These methods have shown a significant decrease of rain, starting from the hydrological year 1975/1976. These same approaches were also used to analyse series of flows spread over a longer period. This fact revealed three periods of drought which are 1940–1945, 1955–1967 and the most recent one highlighted by the rainfall series, starts at the year 1975/1976. The regularized water volume of the dam, calculated from the series of flow rates, is around 37 million m3. This value reflects a deficit of 40% of the regularized volume predicted by the designers of the dam.