Conjunctive use of water resources as an alternative to a leaky reservoir in a mountainous, semiarid area (Adra River basin, SE Spain)

Regulatory actions taken in the Adra River basin (746 km²), located south of the Sierra Nevada Mountains (SE Spain), are analyzed. The Benínar Reservoir (60 hm³), which entered into service in 1983, has suffered from severe leakage from the outset, preventing it from performing the water management functions originally foreseen for it; however, it has also made it possible to determine the response of the underlying carbonate aquifer into which the reservoir water is draining. This response has been studied based on historical data as well as the occurrence of an extraordinary recharge produced by a period of exceptionally heavy rainfall. A conceptual model of the system’s functioning has been established by analyzing leakage rates, piezometric variations, the discharge through the only spring in the area (the Fuentes de Marbella spring) and the physical-chemical characteristics of the aquifer water. Geological and structural aspects of the carbonate formation were also included. An alternative solution for water regulation in the river basin is proposed: the construction of a smaller dam downstream from the spring. This dam would induce recharge through the permeable base of the reservoir, raise the piezometric level and thus increase its storage capacity, as well as control and regulate the water discharged from the spring.