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Accueil du site → Doctorat → Allemagne → 2012 → Modeling hydrological processes in a semi-arid mountainous catchment at the regional scale (Upper Drâa Valley (Morocco))

Rheinischen Friedrich-Wilhelms-Universität Bonn (2012)

Modeling hydrological processes in a semi-arid mountainous catchment at the regional scale (Upper Drâa Valley (Morocco))

Henning Georg Kaspar Busche

Titre : Modeling hydrological processes in a semi-arid mountainous catchment at the regional scale (Upper Drâa Valley (Morocco)

Auteur : Henning Georg Kaspar Busche

Université de soutenance : Rheinischen Friedrich-Wilhelms-Universität Bonn

Grade : Dr. rer. nat. 2012

In the Upper Drâa Valley (14,988 km²) on the southern slopes of the Moroccan High Atlas Mountains, a highly variable precipitation and large evaporation losses cause major water availability problems. The combined effect of projected increase in water demand and temperature and a decrease in precipitation poses a major challenge for water managers in the region. To assess the actual state of the hydrological system (1978-2007), but also the impacts of future changes (2000-2049) a conceptual model, adapted to the characteristics of a semiarid mountainous environment, has been applied. A spatially explicit altitudinal representation, an oasis-irrigation routine, a second linear storage aquifer and a reservoir management module have been implemented in the SWAT model, extending it to SWATMAROC (SWAT-Mountainous and Arid Regions Oriented Concept). During the validation period the model performs well on a monthly timescale at the basin outlet (CME : 0.89) and satisfactorily at the two main tributaries Oued Ouarzazate (CME : 0.69) and Oued Dades (CME : 0.62). Furthermore model results are in line with validation data obtained from groundwater, snow and irrigation studies. Nevertheless the model exhibits flaws in representing water availability in groundwater-fed oases and soil water dynamics. Considering the variable sources of uncertainty, especially in arid and mountainous regions, a wide-ranging uncertainty assessment scheme, quantifying and comparing uncertainties with a signal-to-noise ratio, has been developed and applied. Uncertainties from the hydrological model are highest, followed by divergent signals from climate change ensembles, while the downscaling method has only minor effects on model results. It has been shown that climate change effects for the period 2000-2029 are subject to considerable uncertainties and no clear trends could be identified. For the period 2020-2049 the following developments are “likely” according to the IPCC terminology. Despite a decrease in precipitation (-11%) and especially snowfall (-31%), irrigation water availability in the surface water dependent oasis remains high enough (-5%) to sustain agriculture to the current extent. In contrast, water availability at the reservoir is decreasing disproportionately high (-17%). Therefore the potential for riparian conflicts between the Upper Drâa and the Middle Drâa might augment. A further finding is that the reservoir Mansour-Eddahbi is likely to become inoperable due to siltation in the period 2030-2042, dependent on the assumed pathways of socio-economic development.


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