Snowmelt infiltration and storage within a karstic environment, Vers Chez le Brandt, Switzerland

Abstract

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.

Infiltration under snow cover: Modeling approaches and predictive uncertainty

“…The three flow routing components include the site's upper mineral system composed of silty soils and a clay accumulation horizon, the underlying mineral system made up of clayey soils and the epikarst and lastly a shallow karstic drainage pathway/network originating in the silty-soil horizon. An in depth discussion on the study site's pedology, lithology, karstification, and recharge zone determination has been presented by Meeks and Hunkeler (2015). As demonstrated by Meeks and Hunkeler (2015), shallow vadose zone processes can have a governing role in karst aquifer dynamics, as is the case at the VCB and Areuse Catchment, and that assessment of infiltration in sub-catchments can shine light on aquifer-scale infiltration, storage and drainage patterns.…”

“…An in depth discussion on the study site's pedology, lithology, karstification, and recharge zone determination has been presented by Meeks and Hunkeler (2015). As demonstrated by Meeks and Hunkeler (2015), shallow vadose zone processes can have a governing role in karst aquifer dynamics, as is the case at the VCB and Areuse Catchment, and that assessment of infiltration in sub-catchments can shine light on aquifer-scale infiltration, storage and drainage patterns. Further the VCB site aligns with DeWalle and Rango (2008) suggested optimal conditions for direct percolation of melt water into the subsurface: negligible slope, lack of soil frost and permeable soils and strata.…”

“…The size of the VCB1 catchment area was identified using a series of isolated summer rain events of varying intensity and duration, as observed in VCB1 hydrograph records (Meeks and Hunkeler, 2015). The integrated area (m 3 ) under each summerstorm event hydrograph was divided by its corresponding totalevent precipitation (m), resulting in a recharge area (m 2 ).…”

“…This effect is not considered here. An in-depth discussion on the validity of using a catchment area of 1600 m 2 , despite the influences of a timevariant catchment size, is presented in Meeks and Hunkeler (2015).…”

“…This researcher stated that snowmelt runoff from a larger ''natural lysimeter", a well defined catchment with an easily-monitored drainage point, would provide a conceptually better basis for evaluating output from snowmelt models than the somewhat artificial sampling of snowpack outflow by lysimeters and snow pillows. In following, the karstified Vers Chez les Brant (VCB), which can be viewed as an oversized, real-world lysimeter, consists of a 1600 m 2 watershed that drains infiltrating water to a cave discharge point (VCB1) 53 m below the ground surface (Meeks and Hunkeler, 2015). We used this rather unique natural lysimeter to evaluate the uncertainty surrounding modeled snowmelt predictions.…”