Sustainability of intensive groundwater development: experience in Spain

Intensive aquifer development is common in arid and semiarid countries. The associated economic and social benefits are great, but management is needed and sustainability has to be analysed in the framework of a sound hydrogeological background which includes recharge as a key term. Recharge under natural conditions may greatly differ from the actual value under groundwater exploitation conditions when the aquifer is connected to surface water bodies or evaporation conditions are modified. Actual recharge is not an aquifer property but is variable depending on groundwater abstraction and its pattern, and changes in surface water-groundwater relationships and other circumstances, such as return irrigation flows, leakages, and activities to artificially modify it. Groundwater plays an important role in nature as it sustains spring flow, river base flow, wetlands, and crypto-wetlands, and the related provision of ecological services to mankind. Therefore, developable groundwater resources and their sustainability have to take into account concurrence and the net benefits of capturing it in a given moment and not in other circumstances, and exchanging groundwater-related nature services for the human use of groundwater. The often large storage relative to annual flow of aquifers implies that aquifer development produces effects that may last decades and even affect upcoming human generations. This new dimension, which has economic and sustainability aspects, is not as important for other water resources. Critical flow thresholds have to be considered for groundwater-dependent ecosystems. This is considered from the point of view of water quantity, which is the dominant aspect under arid and semiarid conditions. However, water quality may be as or more important for humans and for nature services, but this needs a separate treatment. The hydrogeological and socio-economic aspects of aquifer behaviour are presented taking into account the experience drawn from some intensively exploited and economically and socially important aquifers, mostly those in La Mancha, in central Spain, but also other intensively exploited Spanish aquifers. Topdown-down administrative decisions to get a given sustainable have resulted in partial failures, but if action is agreed among stakeholders better outcomes could be achieved. Mixed solutions seem the best approach.