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Barcelona, Spain

Raposo J.R.,University of Santiago de Compostela | Molinero J.,Amphos XXI | Dafonte J.,University of Santiago de Compostela
Engineering Geology | Year: 2010

Drawdown produced by excavations can cause geotechnical, hydrologic, environmental and social impacts. The impact and drying up of private wells and springs closer the axis tunnel may become relevant in densely populated rural areas without municipal water supply. A procedure for environmental monitoring of a tunnel excavation and for quantitative evaluation of the hydrogeological impact by means of water balance models in the affected river basins is presented. Once these models have been calibrated against undisturbed conditions, comparison of measured and predicted water table evolution can be used to distinguish actual tunnel impacts from natural oscillations. This procedure has been applied successfully to a case study of tunnel construction in fractured granitic bedrock in the NW of Spain. A hydrogeological impact has been detected and quantified in 5 of 17 monitored points. The small amounts of groundwater drained by the tunnel (less than 5 l/s) produced significant drawdown (5-86 m), on account of the low storage coefficient of the rock massif, causing important damage to private groundwater users. An increase on groundwater recharge rate after the tunnel impact has been identified, that will speed up the process of recovery of the aquifers. The detection and quantification of the main impacts of the excavation could help to take decisions about rectification measures or compensations to the affected groundwater users and about the advisability of the total or partial waterproofing of the tunnel. © 2010.

Elio J.,Fundacion Ciudad de la Energia CIUDEN | Ortega M.F.,Technical University of Madrid | Chacon E.,Technical University of Madrid | Mazadiego L.F.,Technical University of Madrid | Grandia F.,Amphos XXI
International Journal of Greenhouse Gas Control | Year: 2012

Fundación Ciudad de la Energía (CIUDEN) is carrying out a project of geological storage of CO 2, where CO 2 injection tests are planned in saline aquifers at a depth of 1500m for scientific objectives and project demonstration. Before any CO 2 is stored, it is necessary to determine the baseline flux of CO 2 in order to detect potential leakage during injection and post-injection monitoring.In November 2009 diffuse flux measurements of CO 2 using an accumulation chamber were made in the area selected by CIUDEN for geological storage, located in Hontomin province of Burgos (Spain). This paper presents the tests carried out in order to establish the optimum sampling methodology and the geostatistical analyses performed to determine the range, with which future field campaigns will be planned. © 2012 Elsevier Ltd.

Raposo J.R.,University of Santiago de Compostela | Molinero J.,Amphos XXI | Dafonte J.,University of Santiago de Compostela
Hydrology and Earth System Sciences | Year: 2012

Quantifying groundwater recharge in crystalline rocks presents great difficulties due to the high heterogeneity of the underground medium (mainly, due to heterogeneity in fracture network, which determines hydraulic parameters of the bedrock like hydraulic conductivity or effective porosity). Traditionally these rocks have been considered to have very low permeability, and their groundwater resources have usually been neglected; however, they can be of local importance when the bedrock presents a net of well-developed fractures. The current European Water Framework Directive requires an efficient management of all groundwater resources; this 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, dominated by granitic and metasedimentary rocks, was carried out. A water-balance modeling approach was used for estimating recharge rates in nine pilot catchments representatives of both geologic materials. These results were cross-validated with an independent technique, i.e. the chloride mass balance (CMB). A relation among groundwater recharge and annual precipitation according to two different logistic curves was found for both granites and metasedimentary rocks, thus allowing the parameterization of recharge by means of only a few hydrogeological parameters. Total groundwater resources in Galicia-Costa were estimated to be 4427 hm3 yrĝ̂ 1. An analysis of spatial and temporal variability of recharge was also carried out. © Author(s) 2012.

Zona D.,University of Antwerp | Zona D.,San Diego State University | Oechel W.C.,San Diego State University | Richards J.H.,University of California at Davis | And 4 more authors.
Ecology | Year: 2011

The Arctic experiences a high-radiation environment in the summer with 24-hour daylight for more than two months. Damage to plants and ecosystem metabolism can be muted by overcast conditions common in much of the Arctic. However, with climate change, extreme dry years and clearer skies could lead to the risk of increased photoxidation and photoinhibition in Arctic primary producers. Mosses, which often exceed the NPP of vascular plants in Arctic areas, are often understudied. As a result, the effect of specific environmental factors, including light, on these growth forms is poorly understood. Here, we investigated net ecosystem exchange (NEE) at the ecosystem scale, net Sphagnum CO 2 exchange (NSE), and photoinhibition to better understand the impact of light on carbon exchange from a mossdominated coastal tundra ecosystem during the summer season 2006. Sphagnum photosynthesis showed photoinhibition early in the season coupled with low ecosystem NEE. However, later in the season, Sphagnum maintained a significant CO 2 uptake, probably for the development of subsurface moss layers protected from strong radiation. We suggest that the compact canopy structure of Sphagnum reduces light penetration to the subsurface layers of the moss mat and thereby protects the active photosynthetic tissues from damage. This stress avoidance mechanism allowed Sphagnum to constitute a significant percentage (up to 60%) of the ecosystem net daytime CO 2 uptake at the end of the growing season despite the high levels of radiation experienced. © 2011 by the Ecological Society of America.

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