NEWS FROM SOUSS-MASSA

The Souss-Massa catchment covers 4.5% of the Moroccan national area and has a population of 2.33 million of inhabitants. The main activities are agriculture, tourism and fishery. It is the first Moroccan economic pole in agricultural production (85% of fresh vegetable export and 50% of citrus export of Morocco) and climate is arid to semi-arid.

As part of the research activities, the impacts of climate change and human pressures on water resources quantity and quality in the catchment were investigated.

To highlight different processes responsible of water resources variation, a large collection of previous historical databases and studies and many supplementary sampling campaigns for surface and ground water were performed concerning all the parts of the Sous-Massa basin (i.e. recharge area, irrigated perimeters, coastal area, different crop area). The investigation covered all sampling Procedures for Chemical and Isotope Hydrology in the field, in order to explain the problems posed for quality and water resources management. Since the acquisition of data requires a lot of time, infrastructure and resources, the use of chemical and isotopic tracers was necessary. The general utility of geochemical (TDS, Cl, NO₃, Br, Sr, ..) and isotopic tracers (¹⁸O, ²H, ¹⁴C, ¹³C,  ..) is demonstrated, especially for obtaining information inaccessible by other means or investigations. This is particularly true in arid and semi-arid zones where conventional techniques encounter more difficulties in application. All samples were analysed in the lab for major cations, anions, some tracers and stables isotopes.

These analyses allowed to exhaustively investigate the natural and artificial recharge modalities of the aquifers (e.g.¹⁸O and ²H); phenomena of evaporation and infiltration;  river - groundwater relationships; dating of water by radioactive isotopes (e.g.¹⁴C, ³H, ...); origin of salinity (marine intrusion and evaporites), and anthropogenic pollution (liquid and solid discharges, agricultural activities).

The climate database and scenarios simulation indicate a clear tendency to rain diminution and warm conditions. Continuous depletion of groundwater is observed in all the area of the aquifer system due to overexploitation and climate change. The quality of water is variable in time and space mainly and the anthropogenic impact is due to agricultural activities.

Among others, the next steps will consist on modelling the water quality of the water table on the basis of the available data; additional sampling campaigns to clarify the origin of contamination in some areas with high nitrates; mapping and projection of crop water requirements and potential evapotranspiration over the period 2030-2049; establishing the socio-economic aspects based on the new results.