Groundwater salinity and hydrochemical processes in the volcano-sedimentary aquifer of La Aldea, Gran Canaria, Canary Islands, Spain.
The origin of the groundwater salinity and hydrochemical conditions of a 44km(2) volcano-sedimentary aquifer in the semi-arid to arid La Aldea Valley (western Gran Canaria, Spain) has been studied, using major physical and chemical components. Current aquifer recharge is mainly the result of irrigation return flows and secondarily that of rainfall infiltration. Graphical, multivariate statistical and modeling tools have been applied in order to improve the hydrogeological conceptual model and identify the natural and anthropogenic factors controlling groundwater salinity. Groundwater ranges from Na-Cl-HCO3 type for moderate salinity water to Na-Mg-Cl-SO4 type for high salinity water. This is mainly the result of atmospheric airborne salt deposition; silicate weathering, and recharge incorporating irrigation return flows. High evapotranspiration produces significant evapo-concentration leading to relative high groundwater salinity in the area. Under average conditions, about 70% of the water used for intensive agricultural exploitation in the valley comes from three low salinity water runoff storage reservoirs upstream, out of the area, while the remaining 30% derives from groundwater. The main alluvial aquifer behaves as a short turnover time reservoir that adds to the surface waters to complement irrigation water supply in dry periods, when it reaches 70% of irrigation water requirements. The high seasonality and intra-annual variability of water demand for irrigation press on decision making on aquifer use by a large number of aquifer users acting on their own.
Departamento de Física (GEOVOL), Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain. Electronic address: tcruz@proyinves.ulpgc.es.
Tatiana
T
Cruz-Fuentes
Departamento de Física (GEOVOL), Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain. Electronic address: mcabrera@dfis.ulpgc.es.
María del Carmen
Mdel C
Cabrera
Geological Institute of Spain (IGME), Ríos Rosas, 23, 28003 Madrid, Spain. Electronic address: j.heredia@igme.es.
Javier
J
Heredia
Groundwater Hydrology Group, Department of Geo-Engineering, Technical University of Catalonia (UPC), Jordi Girona, 1-3, 08034 Barcelona, Spain. Electronic address: emilio.custodio@upc.edu.
Emilio
E
Custodio
D004784:Environmental Monitoring; D060587:Groundwater / Q000737:chemistry*; D054712:Salinity; D012492:Salts / Q000032:analysis*; D013030:Spain; D014873:Water Pollutants / Q000032:analysis*; D014881:Water Supply / Q000032:analysis* / Q000706:statistics & numerical data
D012492:Salts; D014873:Water Pollutants
Canary Islands; Hydrogeochemistry; Modeling; Return irrigation flows; Salinization processes; Volcanic–sedimentary aquifer