We modified a passive capillary sampler (PCS) to collect snowmelt water for isotopic analysis. Past applications of PCSs have been to sample soil water, but the novel aspect of this study was the placement of the PCSs at the ground-snowpack interface to collect snowmelt. We deployed arrays of PCSs at 11 sites in ten partner countries on five continents representing a range of climate and snow cover worldwide. The PCS reliably collected snowmelt at all sites and caused negligible evaporative fractionation effects in the samples. PCS is low-cost, easy to install, and collects a representative integrated snowmelt sample throughout the melt season or at the melt event scale. Unlike snow cores, the PCS collects the water that would actually infiltrate the soil; thus, its isotopic composition is appropriate to use for tracing snowmelt water through the hydrologic cycle. The purpose of this Briefing is to show the potential advantages of PCSs and recommend guidelines for constructing and installing them based on our preliminary results from two snowmelt seasons.
We present the results of a series of measurements that were made between 1988 and 1992 at Lisi (Georgia). Water level variations in the Lisi well, barometric pressure, precipitation (including rain and snow) and temperature measurements were made during this period. A hydraulic ‘slug test’ has been performed more recently in the well. Two major seismic events occurred during the observation period in the Caucasus area. The Spitak seismic event of 1988 December 9, 110 km from the Lisi borehole, left a clear post‐seismic hydraulic signature, whereas the second event, that of 1991 April 29, 125 km from the borehole, did not seem to induce any detectable anomaly. First, we analyse the tidal and barometric responses of the water level in order to calibrate the borehole and to determine the hydraulic parameters of the aquifer. Then we develop a model for aquifer recharge by meteoric precipitation. Finally, we compare our model with the observed water level variations in the well. We highlight anomalous behaviour that correlates with the earthquake, with the following characteristics: the water level drops about 75 cm with a time constant of 6.6 days. The initial water level is never recovered and the change appears permanent on the scale of the period of observation. Since it is delayed in time, the anomalous water level cannot be attributed to coseismic deformation. Following the suggestion of some authors that the observed behaviour could be related to damage of the aquifer due to the passage of seismic waves, we attempted to take this process into account and to model the resulting water level variations in the aquifer. A double porosity model (including fractures and a porous medium) has been used to describe the modifications undergone by the medium. The medium is discretized at two different scales—(1) at the scale of a porous block and (2) at the scale of the fractured system (which may include a finite number of porous blocks). Using this basic model we have tested three interpretative models: (1) a variable‐permeability model; (2) a locally varying porosity model; (3) a model combining (1) and (2). We show that an increase in permeability by a factor of 2 is needed in order to describe the permanent water level drop, whilst the locally varying porosity zones account for the observed time constants of the anomaly. Using this model, simulations show that we are able to describe water level variation associated with precipitation for the whole period of observation.
Abstract. To evaluate how summer low flows and droughts are affected by the winter snowpack, a Tri-National effort will analyse data from three catchments: Alpbach (Prealps, central Switzerland), Gudjaretis-Tskali (Little Caucasus, central Georgia), and Kamenice (Jizera Mountains, northern Czech Republic). Two GIS-based rainfall-runoff models will simulate over 10 years of runoff in streams based on rain and snowfall measurements, and further meteorological variables. The models use information on the geographical settings of the catchments together with knowledge of the hydrological processes of runoff generation from rainfall, looking particularly at the relationship between spring snowmelt and summer droughts. These processes include snow accumulation and melt, evapotranspiration, groundwater recharge in spring that contributes to (the) summer runoff, and will be studied by means of the environmental isotopes 18 O and 2 H. Knowledge about the isotopic composition of the different water sources will allow to identify the flow paths and estimate the residence time of snow meltwater in the subsurface and its contribution to the stream. The application of the models in different nested or neighbouring catchments will explore their potential for further development and allow a better early prediction of low-flow periods in various mountainous zones across Europe. The paper presents the planned activities including a first analysis of already available dataset of environmental isotopes, discharge, snow water equivalent and modelling experiments of the (already) available datasets.
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