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Cruz-Fuentes T.,University of Las Palmas de Gran Canaria | Cabrera M.D.C.,University of Las Palmas de Gran Canaria | Heredia J.,Geological Institute of Spain IGME | Custodio E.,University of Barcelona
Science of the Total Environment

The origin of the groundwater salinity and hydrochemical conditions of a 44km2 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. © 2014 Elsevier B.V. Source

Cruz-Fuentes T.,University of Las Palmas de Gran Canaria | Heredia J.,Geological Institute of Spain IGME | Cabrera M.C.,University of Las Palmas de Gran Canaria | Custodio E.,University of Barcelona
Hydrogeology Journal

In many arid and semi-arid areas, intensive cultivation is practiced despite water commonly being a limiting factor. Often, irrigation water is from local aquifers or imported from out-of-area aquifers and surface reservoirs. Irrigation return flows become a significant local recharge source, but they may deteriorate aquifer water quality. La Aldea valley, located in the western sector of Gran Canaria Island (Atlantic Ocean), is a coastal, half-closed depression in altered, low-permeability volcanics with alluvium in the gullies and scree deposits over a large part of the area. This area is intensively cultivated. Irrigation water comes from reservoirs upstream and is supplemented (average 30 %) by local groundwater; supplementation goes up to 70 % in dry years, in which groundwater reserves are used up to exhaustion if the dry period persists. Thus, La Aldea aquifer is key to the water-supply system, whose recharge is mostly from return irrigation flows and the scarce local rainfall recharge on the scree formations, conveyed to the gully deposits. To quantify the hydrogeological conceptual model and check data coherence, a simplified numerical model has been constructed, which can be used as a tool to help in water management. © 2014 Springer-Verlag Berlin Heidelberg. Source

Jodar J.,University of Barcelona | Custodio E.,University of Barcelona | Liotta M.,The Second University of Naples | Liotta M.,Italian National Institute of Geophysics and Volcanology | And 6 more authors.
Science of the Total Environment

The time series of stable water isotope composition relative to IAEA-GNIP meteorological stations located in alpine zones are analyzed in order to study how the amplitude of the seasonal isotopic composition of precipitation (Aδ) varies along a vertical transect. A clear relationship between Aδ and local evaporation is obtained, with slopes of -0.87 ‰/100mm/yr and -7.3 ‰/100mm/yr for Aδ18O and Aδ2H, respectively. When all sampling points of the vertical transect receive the same moisture sources, then a linear relationship between Aδ and elevation is obtained, with vertical gradients of 0.16 ‰/100mm/yr and 1.46 ‰/100mm/yr forAδ18O and Aδ2H, respectively. © 2015. Source

Herrera C.,Catolica del Norte University | Custodio E.,University of Barcelona | Chong G.,Catolica del Norte University | Lamban L.J.,Geological Institute of Spain IGME | And 8 more authors.
Science of the Total Environment

Laguna Tuyajto is a small, shallow saline water lake in the Andean Altiplano of northern Chile. In the eastern side it is fed by springs that discharge groundwater of the nearby volcanic aquifers. The area is arid: rainfall does not exceed 200mm/year in the rainiest parts. The stable isotopic content of spring water shows that the recharge is originated mainly from winter rain, snow melt, and to a lesser extent from some short and intense sporadic rainfall events. Most of the spring water outflowing in the northern side of Laguna Tuyajto is recharged in the Tuyajto volcano. Most of the spring water in the eastern side and groundwater are recharged at higher elevations, in the rims of the nearby endorheic basins of Pampa Colorada and Pampa Las Tecas to the East. The presence of tritium in some deep wells in Pampa Colorada and Pampa Las Tecas indicates recent recharge. Gas emission in recent volcanoes increase the sulfate content of atmospheric deposition and this is reflected in local groundwater. The chemical composition and concentration of spring waters are the result of meteoric water evapo-concentration, water-rock interaction, and mainly the dissolution of old and buried evaporitic deposits. Groundwater flow is mostly shallow due to a low permeability ignimbrite layer of regional extent, which also hinders brine spreading below and around the lake. High deep temperatures near the recent Tuyajto volcano explain the high dissolved silica contents and the δ18O shift to heavier values found in some of the spring waters. Laguna Tuyajto is a terminal lake where salts cumulate, mostly halite, but some brine transfer to the Salar de Aguas Calientes-3 cannot be excluded. The hydrogeological behavior of Laguna Tuyajto constitutes a model to understand the functioning of many other similar basins in other areas in the Andean Altiplano. © 2015 Elsevier B.V. Source

Jodar J.,University of Barcelona | Lamban L.J.,Geological Institute of Spain IGME | Medina A.,University of Barcelona | Custodio E.,University of Barcelona
Journal of Hydrology

This work presents the analytical solution to the convolution integral by taking into account the most widely used lumped parameter hydrogeological models (Piston, Exponential, combined Exponential-Piston and Dispersion model) and the eight most typical input tracer functions (Constant; Sinusoidal with linear trend; Sinusoidal with combined sinusoidal and linear trend; Instantaneous pulse injection; Step or Heaviside; Instantaneous pulse with exponential ending; Long pulse with sharp ending; Long pulse with exponential ending) naturally occurring or usually conducted in aquifer systems under natural gradient conditions. For such cases, the output tracer function is expressed in terms of mathematical elementary functions that only depend on the aquifer mean transit time and the parameters belonging to the assumed lumped model. © 2014 Elsevier B.V. Source

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