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

Author(s): J. R. Raposo | J. Molinero | J. Dafonte

Journal: Hydrology and Earth System Sciences Discussions
ISSN 1812-2108

Volume: 9;
Issue: 2;
Start page: 1919;
Date: 2012;
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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 Hm3 yr−1. An analysis of spatial and temporal variability of recharge was also carried out.

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