Long-term assessment of water resources and agricultural changes across a semiarid Mediterranean piedmont (High-Atlas, Morocco)

The Mediterranean region has experienced accelerated socioeconomic development, primarily due to population expansion. This had a substantial influence on water resource availability, with arid and semiarid areas being the most affected. In Morocco, both surface water and groundwater are already affected by reduced precipitation and massive withdrawals due to the growing demand for irrigated agriculture. The present study is carried out in the piedmont of the High-Atlas Mountains (central Morocco). This agro-hydrosystem is mainly fed by intermittent and ephemeral wadis that cross through the piedmont to the Haouz plain and discharge into the mainstream Tensift wadi. Groundwater is used for drinking purposes and serves as a buffer reserve for irrigation during dry seasons. A comprehensive analysis of hydro-climatological data between 1970 and 2018 is performed together with associated agricultural land use trends over the period 1984-2020. Over 48 years of monitoring, the analyses revealed a substantial decrease of water resources. The standardized precipitation index (SPI) showed three main meteorological drought periods, 1982-1986, 1998-2008 and 2013-2017. A decreasing trend of streamflow by nearly 40% has been noticed. The groundwater level has been decreasing dramatically over the last 2 decades.  Surprisingly, this decrease in water resources was associated to an agricultural transition from seasonal crops (cereals) to perennial crops (olive trees). This conversion is likely to exacerbate the water shortage, leading to an overexploitation of groundwater resources to satisfy the growing agricultural demand.

Keywords: Mediterranean region, precipitation, groundwater, streamflow, LULC, trends.