The use of a hydrological-economic model to assess sustainability in groundwater-dependent agriculture in drylands

This paper deals with the assessment of sustainability in the exploitation of groundwater by agriculture in arid and semi-arid lands. The procedure proposed is not based on an indicator made up of a few partial, static figures, but on one which requires the use of all the information collectable for the system under assessment. This information serves to calibrate a dynamic model which formalizes the main causal chains and feedbacks existing between hydrogeology and the number of farms, this being ultimately linked to farms economy. The risk of overexploitation is worked out as the percentage of model’s long-term steady-states, associated to a great number of different scenarios, surpassing some chosen threshold marking out sustainability from degradation. The procedure has been implemented for two study cases: the Eastern La Mancha aquifer (Spain), where information was abundant, and the Oued-Mird alluvial aquifer (Morocco), where quantitative information was so much scarcer. Significant risks of degradation have been found in both cases, especially in the Moroccan one.