Climate change impact assessment on a carbonate aquifer under semi-arid climate: example of the Cenomanian-Turonian aquifer within Meskala-Ouazzi region (Essaouira Basin, Morocco)

This study aims to assess the climate change impact on water resources of the Essaouira Basin (Morocco). The rainfall index shows a significant interannual variability which is organized in an alternation of the excess period (1940–1956), two deficit periods (1956–1986 and 1998–2015) separated by a normal period (1986–1998). The statistical approach reveals the presence of a break in 1956 with a rainfall deficit of 14.45% and that the temperatures show a general upward trend with a warming of 2.3 °C for mean and minimum temperature and of 2.8 °C for maximum and this for the period 1987–2014. Flow rates show a slight upward trend that could be explained by a short and intense rainfall that characterizes our semi-arid environment. Concerning the piezometric approach, it shows a general descent in piezometric surface for the period of observation (reached 12 m in some wells). The downward evolution of piezometric surface due to the decrease of precipitation has resulted in the spatial and temporal degradation of the groundwater quality. A decrease in nitrate levels has been noted; this could be explained by the downward trend in precipitation by favoring the retention of nitrates in the superficial parts of the soil and by limiting their infiltration to the aquifer.