Dealing with seawater intrusion in the Chtouka Aquifer, Morocco

The joint technical cooperation project CREM (Coopération régionale pour une Gestion Durable des Ressources en Eau au Maghreb) of OSS (Observatoire du Sahara et du Sahel), BGR (Federal Institute for Geosciences and Natural Resources), and GIZ (German Society for International Cooperation) is funded by BMZ (German Federal Ministry for Economic Cooperation and Development) and fosters the exchange of groundwater management strategies between the three countries Morocco, Algeria, and Tunisia. The strategic focus in the pilot area of Souss-Massa, Morocco, by BGR is on saltwater intrusion. The Souss-Massa Basin is the country's most important agricultural area. Groundwater from the coastal Chtouka aquifer is the main source for irrigation. The heavy exploitation of groundwater leads to declining water level in the sub-basin, with the effect of intruding seawater from the ocean. Several measurement campaigns were launched together with the ABHSM (Agence de Bassins Hydrauliques Souss-Massa) and the University of Agadir. Wells and monitoring boreholes along the coast were visited, altitudes and water level data were gathered, and depth specific electrical conductivity profiles were taken. Results show an average groundwater depletion of up to 1.5 m per year in several locations. Due to this depletion, a change of the general flow direction in the Chtouka Aquifer was found. The mobilisation of high saline water from the south of the plain and the marine intrusion threaten the irrigated zones. The hydrochemical analyses identified a zone of wells with marine influence. Additional monitoring wells were drilled. A three dimensional density dependent numerical model is used to simulate groundwater flow and the development of salinities in the Chtouka aquifer. Countermeasures are already in progress, e.g. the construction of a water desalination plant for agricultural purposes and a so-called aquifer contract. In international workshops, the project's results, as well as strategies are discussed with the aim to transfer the achievements to other OSS member countries, i.e. Tunesia and Algeria.