Interaction of aquifer-wetland in a zone of intensive agriculture: the case of Campo de Dalias (Almeria, SE Spain)

The Campo de Dalias (Almeria, south-eastern Spain) was the backdrop for the development of intensive agricultural activity during the 1970s. Due to the poor natural soil development, the agriculturalists opted for a system that involved quarrying silt and clay deposits that could be used as soil in the greenhouses. In parallel, poor water quality in the upper aquifer caused the gradual abandonment of boreholes and a generalised rise in piezometric levels. These factors have favoured the formation of a series of artificial wetlands in the abandoned clay pits (Onayar, Cabriles and Balsa del Sapo ("Toad Pond") being the most significant). In Balsa del Sapo, the water column rose 3.5 m between October 2007 and February 2011. There has been a continuous fall in the electrical conductivity of the surface water, which has gone from 14,500 A mu S cm(-1) in 2004 to 4,100 A mu S cm(-1) in 2013. The most recent concentrations are close to those found in the groundwater. The same situation is detected for Cl, SO4 and Na ion concentrations in the surface and groundwater. These data show the groundwater-surface water interaction in the Balsa del Sapo. Nevertheless, the sharp rise in surface water level has created a flood hazard (due to the shallow topography of the area), both for people living in the vicinity and their property. This is an endorheic zone where a number of ramblas (gullies) draining the southern face of the Sierra de Gador mountains converge. The Campo de Dalias is a spectacular example of the changes that can occur in a semiarid agricultural area as a result of intensive groundwater abstraction. These changes are directly related to the management of water resources, the most recent consequence of which is the increased risk of flooding. Hence, there is a need to consider the management of these water resources to achieve a more sustainable use, which is compatible with the environmental protection of the wetland and which will give some guarantee of flood protection for people and property.