Water uptake for agriculture is very intensive in Souss Massa region (521Mm 3 per year), where irrigation waters are almost exclusively pumped from the water table which is being depleted by 2 to 3 meter per year 1 . The climate is very arid with rainfall of about 150-200 mm/year concentrated in winter and Evapotranspiration (ETo) of 1800 mm/year with more than 7 mm/day in the Summer, average winter temperatures can reach 5-7°C whereas average summer temperatures can be as high as 32-36 °C 2-3 . Adding the effect of the foreseen climate change, the available water volumes are expected to shrink by 10-15% of the actual volumes in 2020 due to the falling groundwater levels and the reduction of the storage capacity of dammed lakes by siltation 4 . The citrus sector in the Souss region occupies about 33 000 ha which represents about 40% of the

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Examination of the clay fraction of the Gezira and Kenana soils of the Sudan revealed montmorillonite as the dominant clay mineral, accompanied by kaolinite. The presence of illite and vermiculite is questionable. Quartz was found as an accessory mineral. Most of the kaolinite is concentrated in the 'coarse clay' (2-0.2 pm), whereas more than 90 per cent of the 'line clay' consists of montmorillonite.

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