Locating and characterising groundwater storage areas within an alpine watershed using time‐lapse gravity, GPR and seismic refraction methods

Abstract

Unconsolidated sediments in alpine watersheds can store glacier melt and snowmelt as groundwater, which helps sustain flow in mountain rivers during dry periods. However, the amount and distribution of groundwater storage in rugged alpine terrain is not well understood, hindering our ability to predict the rate and timing of groundwater discharge into alpine streams. We show how non-invasive time-lapse microgravity surveys can be used to gauge the spatial distribution of groundwater storage changes within a large (ca 1500 Â 1000 m) moraine-talus field of the Lake O'Hara alpine watershed of the Canadian Rockies. Additional ground-penetrating radar (GPR) and seismic refraction surveys provide complementary information on subsurface bedrock topography and reveal the location of a major northwest-southeast trending depression that likely controls groundwater flow to an alpine lake contiguous with the moraine-talus field. Repeat relative gravity measurements made on a network of 80 gravity stations over and around the moraine-talus field during the summers of 2009 and 2010 reveal gravity changes of up to 25 mgal. Although the small gravity changes associated with groundwater flowing out of storage areas are noisy, significant changes are evident on the eastern side of the moraine-talus field.

Spatio‐temporal variability in contributions to low flows in the high Alpine Poschiavino catchment

“…We estimated the minimum‐maximum range of surface layer depth for the shallow, intermediate, and deep thickness classes as 0.5–1 m, 3–5 m, and 7–10 m, based on expert judgement, following suggested values in Smoorenburg (), analysing available topographic information. These estimates were compared with results from geophysical investigations in similar environments (e.g., Ardelean, Onaca, Urdea, & Sărășan, ; McClymont et al, ; Volze, ) to assess their plausibility. For every geomorphological feature, we assigned quantitative values for porosity φ (high, medium, low, and [almost] none) and quantified them based on Blume et al () as porosities of 30%, 20%, 10%, and 0%, respectively.…”

Water storage changes as a marker for base flow generation processes in a tropical humid basement catchment (Benin): Insights from hybrid gravimetry

“…Among the recorded measurements at each station, the first ones are usually affected by a nonlinear drift due to transportation [McClymont et al, 2012]. Once the gravimeter is stabilized, the time series converges, and those measurements which are within a 3 lGal range are kept for least square adjustment, making sure the tilts are within the accepted range (0 6 5 arcsec (unit is arc second)) and no particular behavior is identified in the instrument internal temperature.…”

“…The main applications to hydrology of time-lapse microgravity surveys are (1) specific yield estimates [Montgomery, 1971;Lambert and Beaumont, 1977;Cole, 1991;Pool and Eychaner, 1995;Howle et al, 2003;Pool, 2008;Gehman et al, 2009], (2) monitoring water storage changes (WSCs) on specific areas for process identification or water budget estimates [Whitcomb et al, 1980;Naujoks et al, 2008;Chapman et al, 2008;Gettings et al, 2008;McClymont et al, 2012;Pfeffer et al, 2013], and (3) calibration-validation of conceptual or physically based hydrological models Naujoks et al, 2010;Christiansen et al, 2011aChristiansen et al, ,2011b. Only few studies used gravity data to address the link between WSCs and discharge [Jacob et al, 2008;Lampitelli and Francis, 2010;Kroner and Weise, 2011;Creutzfeldt et al, 2012Creutzfeldt et al, , 2014.…”

“…All these considerations impact data accuracy. For instance, instrument transportation and hence the distance between stations is known to affect relative-gravity survey accuracy [McClymont et al, 2012;Masson et al, 2012;Pfeffer et al, 2013]. Gettings et al [2008] reported on a number of studies using many reoccupations and/or several gravimeters to constrain drift and detect nonlinear drifts and tares.…”

Identifying spatial and temporal dynamics of proglacial groundwater–surface-water exchange using combined temperature-tracing methods

“…In contrast to the well investigated effect of climate change on proglacial surface-water systems (e.g., Singh and Bengtsson 2005, Huss et al 2008, Mark 2008, Casassa et al 2009, Stewart 2009, Nolin et al 2010, potential interactions with proglacial groundwater systems have not been investigated in similar detail (Piotrowski 2007). To understand the potential responses and resilience of proglacial groundwater systems to climate change, the processes controlling the spatially and temporally dynamic interactions between ground water and proglacial rivers and lakes have to be identified (Cooper et al 2002, McClymont et al 2012, Langston et al 2013.…”