QUANTITY AND QUALITY OF GROUNDWATER IN THE CAMPO-DE-DALIAS (ALMERIA, SE SPAIN)

The Campo de Delias is the most economically important agricultural area in the whole of the Province of Almeria. A benign climate combined with the expertise of the market gardeners and their intensive cultivation in plastic hot-houses of out-of-season fruit and vegetables has turned a stony wasteland into an area of great productivity. The main water supply comes from a series of wells drilled into the subterranean aquifers running through the local rocks, a geometrically complex succession of Triassic limestones and dolomites, Miocene conglomerates and calcareous sandstones, Pliocene calcarenites and Quaternary gravels, sands and silts. The annual influx into the aquifers has been calculated as being around 50 Hm3, while at the present day more than 100 Hm3 are being taken out during the same period. This over exploitation of the resources is causing an inexorable descent in the water table, which is leading to marine intrusion in those aquifers nearest the sea. The main aquifer-bearing units are Balanegra and Aguadulce, composed essentially of Triassic, Alpujarride carbonates, and the Balerma-Las Marinas unit, made up of Pliocene calcarenites. In the water from some of the wells in the Aguadulce unit more than 10,000 microS/cm have been measured at some distance from the coast, while in the Balanegra unit there are a large number of conoids below sea level, although marine intrusion is at present limited to a fairly narrow coastal strip.