International audienceSources of water use by 10 alluvial trees in various hydrogeological and ecological situations at the Pfyn forest (Wallis canton, Switzerland) were assessed by analysing 18O and 2H isotopes of precipitation, soil water at different depths, surface water, groundwater and xylem sap. The soil water line in a δ18O versus δ2H diagram shows evidence of kinetic fractionation related to evaporation. The tree water line is close to the soil trend; however, an additional enrichment may occur and could be related to xylem–phloem communication under water stress. At sites where the water table was at least 2 m below the ground surface, isotopic temporal variability of soils and trees was strongly linked with seasonal variation of soil water content. When soil water content was low and water table shallow, trees used both soil water and groundwater. When soil water content was high, this source was usually the dominant source for transpiration. In addition, some ecological strategies, reproduction or growth competition, could explain shifts in the utilization of different water sources, for example, from soil water to a mix of soil water and groundwater. At one site where soil water and groundwater were abundant throughout the year (next to the river course), neighbouring trees permanently used distinct water sources. This is consistent with a strategy of competition limitation, which would favour bank colonization. These results provide insight into the ecohydrological functioning of this system and will aid future management responses to both local and climate changes

consumption and groundwater-dependent ecosystems as two receptors with respect to which groundwater should be protected from deterioration and chemical pollution. From this perspective it is even more appropriate to assess groundwater vulnerability not for the whole groundwater body but for particular receptors like abstraction wells or groundwater-dependent ecosystems.A fundamental difficulty in assessing groundwater vulnerability is the complexity of groundwater systems. The intertwined processes of groundwater flow and pollutant transport occur in three spatial dimensions, in the inherently heterogeneous and anisotropic geological media, over a great range of distances and times, and are typically nonstationary. Also, the pressures on groundwater quality have complex or unknown spatial and temporal distribution characteristics. The vulnerability of a particular groundwater receptor is therefore a complex function of the following:spatial and temporal distribution of pressures, for example, location of source areas of pollution, pollutant loads, fertilization levels, location of pumping wells and their pumping regimes, patterns of land-use change; distribution of water flow paths in the groundwater body; dilution, retardation, attenuation, and transformations of contaminants in the subsurface that affect their levels at the receptor; rates at which impacts of pressures propagate along the flow paths, that is, time lags associated with the responses of the receptor to the commencement or cessation of pressures. The task of assessing groundwater vulnerability can thus be seen as essentially equivalent to predicting contaminant concentrations within the groundwater body or at the groundwater receptors. A direct and comprehensive assessment of groundwater vulnerability is in most cases not feasible due to insufficient availability of monitoring data and the inherent complexity of groundwater systems. Instead, groundwater vulnerability indicators are defined, quantified, and mapped in order to reflect the actual or to predict the potential severity of human-induced deterioration in groundwater quality. Furthermore, because of time lags inherent to the groundwater flow and contaminant transport, responses in groundwater quality to changes in contaminant inputs may not be visible over short periods of time of the order of years that are typically considered by policy makers, ground-water managers, and the general public. Setting up of deadlines for the improve-ment of surface water quality-as, for example, in programs of measures required by the Water Framework Directive-involves consideration of such time lags (Witczak et al., 2007;Fenton et al., 2011;Aquilina et al., 2012;Hamilton, 2012; Herrman et al., 2012; Stumpp et al., not published yet).This work presents different understandings of the groundwater vulnerability concept and gives an overview of methods for assessing the intrinsic vulnerability. Among those, only the physically based methods can provide physically meaningful and operational indicators of the i...

a b s t r a c tGroundwater recharge from snowmelt represents a temporal redistribution of precipitation. This is extremely important because the rate and timing of snowpack drainage has substantial consequences to aquifer recharge patterns, which in turn affect groundwater availability throughout the rest of the year. The modeling methods developed to estimate drainage from a snowpack, which typically rely on temporallydense point-measurements or temporally-limited spatially-dispersed calibration data, range in complexity from the simple degree-day method to more complex and physically-based energy balance approaches. While the gamut of snowmelt models are routinely used to aid in water resource management, a comparison of snowmelt models' predictive uncertainties had previously not been done. Therefore, we established a snowmelt model calibration dataset that is both temporally dense and represents the integrated snowmelt infiltration signal for the Vers Chez le Brandt research catchment, which functions as a rather unique natural lysimeter. We then evaluated the uncertainty associated with the degree-day, a modified degree-day and energy balance snowmelt model predictions using the nullspace Monte Carlo approach. All three melt models underestimate total snowpack drainage, underestimate the rate of early and midwinter drainage and overestimate spring snowmelt rates. The actual rate of snowpack water loss is more constant over the course of the entire winter season than the snowmelt models would imply, indicating that mid-winter melt can contribute as significantly as springtime snowmelt to groundwater recharge in low alpine settings. Further, actual groundwater recharge could be between 2 and 31% greater than snowmelt models suggest, over the total winter season. This study shows that snowmelt model predictions can have considerable uncertainty, which may be reduced by the inclusion of more data that allows for the use of more complex approaches such as the energy balance method. Further, our study demonstrated that an uncertainty analysis of model predictions is easily accomplished due to the low computational demand of the models and efficient calibration software and is absolutely worth the additional investment. Lastly, development of a systematic instrumentation that evaluates the distributed, temporal evolution of snowpack drainage is vital for optimal understanding and management of cold-climate hydrologic systems.

Even though karstic aquifers are important freshwater resources and frequently occur in mountainous areas, recharge processes related to snowmelt have received little attention thus far. Given the context of climate change, where alterations to seasonal snow patterns are anticipated, and the often-strong coupling between recharge and discharge in karst aquifers, this research area is of great importance. Therefore, we investigated how snowmelt water transits through the vadose and phreatic zone of a karst aquifer. This was accomplished by evaluating the relationships between meteorological data, soil-water content, vadose zone flow in a cave 53 m below ground and aquifer discharge. Time series data indicate that the quantity and duration of meltwater input at the soil surface influences flow and storage within the soil and epikarst. Prolonged periods of snowmelt promote perched storage in surficial soils and encourage surficial, lateral flow to preferential flow paths. Thus, in karstic watersheds overlain by crystalline loess, a typical pedologic and lithologic pairing in central Europe and parts of North America, soils can serve as the dominant mechanism impeding infiltration and promoting shallow lateral flow. Further, hydrograph analysis of vadose zone flow and aquifer discharge, suggests that storage associated with shallow soils is the dominant source of discharge at time scales of up to several weeks after melt events, while phreatic storage becomes import during prolonged periods without input. Soils can moderate karst aquifer dynamics and play a more governing role on karst aquifer storage and discharge than previously credited. Overall, this signifies that a fundamental understanding of soil structure and distribution is critical when assessing recharge to karstic aquifers, particularly in cold regions.

This document describes the design of a concept for a pipe-traversing robot and its end-product. The purpose of this document is to describe a design and fabrication of a robot capable of traversing a dryer ventilation system in order to clean it. Speed, effectiveness, weight, and cost were all major criteria used during the design process. The primary goal for this robot is to reduce the number of annual house fires that occur as a result of improperly maintained dryer ventilation systems.