Contribution of climate change on water resources in semi-aride areas; example of the Essaouita Basin (Morocco)

Abstract

The groundwaters in semi-arid regions are subject to the impact of climatic and anthropogenic pressures. In the case of coastal aquifers, the vulnerability that arises is compounded by the risk of seawater intrusion. The joint application of several methodologies hydrodynamic and isotopic to the aquifer's coastal Essaouira basin in semiarid region of Morocco has established a diagnosis of the current state of the aquifer and the risks it is submitted. This area includes two main superimposed aquifers. The Plio-Quaternary, which provides most of the water supply, is a reservoir is mostly sand, sandstone and conglomerates. Turonian calcareous dolomite is seeking recently by deep wells to supply drinking water to the city of Essaouira. The study area to form a syncline at heart Senonian is between two structures has diapiric Triassic material: the diapir Tidzi outcropping east and south and the cache of Essaouira diapir WEST, who was detected by the geophysics. In the Essaouira Basin, water resources are less important and are seriously affected by the climate in terms of quantity and quality, rainfall in the area does not exceed 300 mm year -1 on average, the average temperature hovers around 20 °C, potential evapotranspiration is very high, about 920 mm year -1. The main direction of groundwater flow is from southeast to northwest toward the Atlantic Ocean. Essaouira basin is most vulnerable to climate drought since it is recharge is entirely dependent on rainwater. This finding should be incorporated into a management strategy directed towards safeguarding resources.