GROUNDWATER MINING OF THE SOUSS VALLEY ALLUVIAL AQUIFER, MOROCCO

The Souss-Massa River Basin, in southern Morocco, covers approximately 27,000 square kilometers. With a year-round growing season, irrigated agriculture in the river basin produces more than half of Morocco’s exported citrus and vegetables. Total water use in the basin is about 965 million cubic meters per year; approximately 94 per cent of the water use is for irrigation. Although water used for irrigation is obtained from surface water and groundwater sources, these sources are not sufficient to sustain current agricultural practices, and groundwater resources are being depleted.

The reported average recharge rate for the Souss Valley alluvial aquifer is approximately 450 million cubic meters annually; the actual amount varies significantly in response to annual rainfall. On average, groundwater extraction in the basin exceeds recharge by an estimated 260 million cubic meters annually. This over-pumping of the alluvial aquifer has resulted in water level declines ranging from 0.5 to 2.5 meters per year during the past three decades. Continuation of these declines could make pumping uneconomical in some locations by 2010. Groundwater level declines in some areas already have prompted major actions, such as construction of a 80 km canal to transfer water from dams to the Guerdane citrus area that is at high risk. It is interesting to note that this canal diverts water that previously was used for groundwater recharge in other parts of the basin.

Even under the most optimistic forecasts, which assume maximum surface water collection, conversion to drip irrigation, and reuse of treated sewage effluent, the irrigation water supply deficit is projected to reach 50 million cubic meters per year by 2020. Unless major changes in irrigation practices and groundwater management are implemented, agricultural production in the Souss Massa Basin may decline greatly during the next few decades, with economic and social impacts to the region.