Parameterization and quantification of recharge in crystalline fractured bedrocks in Galicia-Costa (NW Spain)

Abstract

Quantification of groundwater recharge in crystalline rocks presents great difficulties due to high heterogeneity. Traditionally these rocks have been considered with very low permeability, and their groundwater resources have been usually neglected, although they can have local importance when the bedrock presents a net of fractures well developed. Current European Water Framework Directive requires an efficient management of all groundwater resources, which begins with a proper knowledge of the aquifer and accurate recharge estimation. In this study, an assessment of groundwater resources in the Spanish hydrologic district of Galicia-Costa, with a geology mainly dominated by granitic and metasedimentaty rocks, was carried out. A water-balance modeling approach was used for estimating recharge rates in nine pilot catchments representatives of both geologic materials, and results were cross-validated with an independent technique as Chloride mass balance (CMB). A relation among groundwater recharge and total precipitation according to two different logistic curves was found for granites and metasedimentary rocks, which allows the parameterization of recharge by means of few hydrogeological parameters. Total groundwater resources in Galicia-Costa were estimated in 4427 Hm<sup>3</sup> yr<sup>−1</sup>. An analysis of spatial and temporal variability of recharge was also carried out

Fresh and saline submarine groundwater discharge in a large coastal inlet affected by seasonal upwelling

“…Furthermore, extrapolating our results on an annual basis and using the maximum recharge of Galician crystalline aquifers determined by Raposo et al (2012), our fresh groundwater discharge estimates represent 10% of the total maximum groundwater recharge for the basin. Using the parametrization of Galician aquifer recharge based on rainfall (Raposo et al 2012) and the annual precipitation over the basin for the 2017–2018 hydrological year, this contribution rises to 20%. Although these numbers should be taken with caution given the large extrapolations, they confirm how reasonable our discharge magnitudes are.…”

“…The surface aquifer unit contained in crystalline rocks and within the regolith has three orders of magnitude higher volumetric water storage capacity than the fractured bedrock underneath. The surface unit also has higher recharge/discharge rates and lateral transmissivities by several orders of magnitude (Mota et al 2004; Ramalho et al 2012; Raposo et al 2012). Thus, the groundwater contained within the regolith is most likely to be the dominant continental groundwater endmember in fresh submarine groundwater discharge into the Ría de Vigo.…”

“…1). The embayment is mesotidal, with an average tidal amplitude of 2.2 m. Climate in the region is oceanic, with average temperatures of ~ 15°C, although there is a large gradient in air temperature, wind speed, evapotranspiration and precipitation from the littoral zone to the mountainous inland (Raposo et al 2012). Precipitation is mainly concentrated during autumn and winter and can vary from ~ 900 mm in the Cíes Islands to ~ 2500 mm at the innermost part of the basin.…”

Mapping the Viability, Time, and Cost of Manual Borehole Drilling in Developing Regions

“…Geospatial information has proven useful to explore the link between water and poverty [18,19]. In the case of groundwater resources, GIS has frequently been applied to delineate groundwater potential areas [20][21][22][23][24], study the spatial distribution of aquifer recharge [25][26][27], or assess the vulnerability of aquifer systems to pollution [28][29][30].…”

Contribución de las técnicas hidroquímicas, isotópicas e hidrodinámicas a la caracterización de acuíferos carbonatados y su relación con la red de flujo superficial. Aplicación al acuífero de Alcadozo (cuenca del Segura)

“…La incertidumbre de los valores de R obtenidos mediante el código Visual Balan está relacionada con los parámetros utilizados en la modelación y sus condiciones. En estudios comparables (Jiménez-Martínez et al, 2010;Raposo et al, 2012) la incertidumbre fue estimada considerando como criterio la sensibilidad relativa de los parámetros en la estimación de la recarga, definida de la siguiente manera:…”