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Snowmelt drives a large portion of streamflow in many mountain areas of the world. However, the water paths from snowmelt to the arrival of the water in the streams are still largely unknown. This work analyzes for first time the influence of snowmelt on spring streamflow with different snow accumulation and duration, in an alpine catchment of the central Spanish Pyrenees. This study presents the water balance of the main melting months (May and June). Piezometric values, water temperature, electrical conductivity and isotope data (δ18O) allow a better understanding of the hydrological functioning of the basin during these months. Results of the water balance calculations showed that snow represented on average 73% of the water available for streamflow in May and June while precipitation during these months accounted for only 27%. However, rainfall during the melting period was important to determine the shape of the spring hydrographs. On average, 78% of the sum of both the snow water equivalent (SWE) accumulated at the beginning of May and the precipitation in May and June converted into runoff during the May–June melting period. The average evaporation‐sublimation during the 2 months corresponded to 8.4% of the accumulated SWE and rainfall, so that only a small part of the water input was ultimately available for soil and groundwater storage. When snow cover disappeared from the catchment, soil water storage and streamflow showed a sharp decline. Consequently, streamflow electrical conductivity, temperature and δ18O showed a marked tipping point towards higher values. The fast hydrological response of the catchment to snow and meteorological fluctuations, as well as the marked diel fluctuations of streamflow δ18O during the melting period, strongly suggests short meltwater transit times. As a consequence of this hydrological behaviour, independently of the amount of snow accumulated and of melting date, summer streamflow remained always low, with only small runoff peaks driven by rainfall events. [ABSTRACT FROM AUTHOR]

The temporal and spatial dynamics of groundwater was investigated in a small catchment in the Spanish Pyrenees, which was extensively used for agriculture in the past. Analysis of the water table fluctuations at five locations over a 6-year period demonstrated that the groundwater dynamics had a marked seasonal cycle involving a wetting-up period that commenced with the first autumn rainfall events, a saturation period during winter and spring and a drying-down period from the end of spring until the end of the summer. The length of the saturation period showed great interannual variability, which was mainly influenced by the rainfall and evapotranspiration characteristics. There was marked spatial variability in the water table, especially during the wetting-up period, which could be related to differences in slope and drainage area, geomorphology, soil properties and local topography. Areas contributing to runoff generation were identified within the catchment by field mapping of moisture conditions. Areas contributing to infiltration excess runoff were correlated with former cultivated fields affected by severe sheetwash erosion. Areas contributing to saturation excess runoff were characterized by a marked spatial dynamics associated with catchment wetness conditions. The saturation spatial pattern, which was partially related to the topographic index, was very patchy throughout the catchment, suggesting the influence of other factors associated with past agricultural activities, including changes in local topography and soil properties. The relationship between water table levels and stream flow was weak, especially during the wetting-up period, suggesting little connection between ground water and the hydrological response, at least at some locations. The results suggest that in drier and human-disturbed environments, such as sub-Mediterranean mountains, saturation patterns cannot be represented only by the general topography of the catchment. They also suggest that groundwater storage and runoff is not a succession of steady-state flow conditions, as assumed in most hydrological models. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: The stream flow response of two neighboring catchments in the central Spanish Pyrenees was compared for 26 rainstorms covering both catchments: one catchment (2.84km2) was extensively used for agriculture in the past, and the other (0.92km2) is covered by dense natural forest. Their similarity in terms of lithology and topography enabled us to separate the effects of soil and land cover on their hydrological responses. Relative to the forested catchment, peak flows in the past agricultural catchment were always greater (566 vs. 119ls−1 km−2), the response time was 2- to 3-fold faster (131 vs. 356min), and the recession limbs were 1–2 orders of magnitude shorter (7 vs. 72h). Storm flow was usually greater in the former agricultural catchment, especially for low–intermediate sized flood events; only for larger events the storm flow in the forested catchment was sometimes greater. Storm flow differences were closely related to catchment wetness conditions and showed a marked seasonal pattern, with higher values in the past agricultural catchment under dry conditions, and usually higher values in the forested catchment under wet conditions. In the past agricultural catchment, runoff was generated during the entire water year, through both surface (i.e. infiltration excess and saturation excess overland flow) and subsurface flow. We suggest that the forested catchment can be characterized by a dual (or switching) behavior controlled by soil moisture conditions, which regulates the hydrological connectivity and favors the release of large amounts of subsurface flow. Differences in soil depth and permeability, together with differences in vegetation cover, may explain the contrasting dominant runoff generation processes operating in each catchment, and consequently the differences between their hydrograph characteristics. [ABSTRACT FROM AUTHOR]

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Copyright of Cuadernos de Investigación Geográfica is the property of Universidad de la Rioja, Servicio de Publicaciones and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article discusses the influence of canopy density on the central Pyrenees mountains in southwest Europe. The authors analysed the spatial variability and different evolution patterns of snowpack in a mixed beech-fir stand in the Pyrenees. They explain that their principal component anaysis provided valuable information in explaining these observations. Their results found a high variability in snow accumulation within forest areas related to differences in their canopy density. They found that the maximum snow water equivalent was reduced by more than 50 percent beneath dense canopies compared with clearings.

Abstract: The Araguás Catchment of the Central Spanish Pyrenees has been monitored since 2004 to study weathering, erosion, and the hydrological and sediment response to rainfall events in order to understand the hydromorphological dynamics of a badland area in a relatively humid environment. This small catchment (0.45 km2) shows highly active processes of physical and chemical weathering related to seasonal variations in temperature and moisture. Erosion and sediment transport are widely studied in badlands within Mediterranean environments because they represent the dominant sediment source. To obtain information about suspended sediment and discharge, a gauging station was installed within the Araguás Catchment during the summer of 2005. The aim of this work is to determine the relationships among rainfall, runoff, and suspended sediment in this badland area. Towards this goal, we analyze the relationships between suspended sediment concentration and discharge during rainfall events. From a hydrological viewpoint, the Araguás Catchment reacts to all rainfall events with torrential flow being the most characteristic hydrological response. The results obtained between October 2005 and April 2007 reveal extremely high concentrations of suspended sediment, with values frequently exceeding 100 g l−