Emme

Emme

Description of the site

This observatory site is located in Aeschau (region of Emmental, Switzerland). The study area (0.8 km2) lies in the Upper part of Emme River Valley, a pre-alpine, alluvial valley situated at the northern margin of the Alps. The underlying aquifer is formed by quaternary deposits, composed of sandy gravels and cobbles, with a variable proportion of silt, and contains lenses of coarse uniform gravel (Käser and Hunkeler, 2015). These features result in an extremely conductive unconfined aquifer. The bedrock underneath the aquifer -and the lower part of it (1-3 m thick)- is considered as an aquitard relative to the upper part of the alluvium. The saturated hydraulic conductivity (Ks) show higher values (5×10-3 m/s) predominantly in the upper 30-35 m of the valley fill, whereas smaller values, around 10-4 m/s or lower, occur mainly deeper (Blau, 1984, 1991; Blau and Muchenberger, 1997; Würsten, 1991).  

The monitored area is crossed by the Emme river, which provides the main source of recharge to the alluvial aquifer through its coarse gravel-bed. This segment of the river also exhibits a couple of small weirs designed for erosion control. The valley at this location has an average width of 400 m and a mean topography gradient of 0.9%.  

An important groundwater abstraction plant -which supplies the 45% of the drinking water for consumption of the city of Bern- is located at the site. The wellfield, consisting of 8 wells, is aligned in parallel to the river Emme in the so-called Ramsei Plain (left side of the river). The total groundwater abstraction rate is on average 24000 l/min (0.4 m3/s). This rate is substantially relative to the total water balance of the system, as it has been proved that the latter is clearly affected by pumping. By no means it can be higher than 50% of the total outflow (Schilling et al., 2017). The bedrock-sediment interface around the Ramsei Plain is on average as deep as 25 m, being the maximum depth 46 m (Würsten 1991). This mean value can be also considered a good estimate of the aquifer thickness for the rest of the study area.  

Regarding the climatic and hydraulic conditions of the site, the average annual precipitation is 1300 mm, the potential evapotranspiration 550 mm and mean annual air temperature 8ºC (Käser and Hunkeler, 2015). The long-term average discharge of the river is 4.4 m3/s. This value is typically higher during the snowmelt periods (March-April) and especially small throughout very dry summers or cold winters, when segments of the Emme river can dry completely dry (Würsten, 1991).

(top) Maps of the Upper Emme catchment and (bottom) a close-up of the GW pumping station on the Ramsei Plain in the lower part of the catchment. In the top image, bright blue colors in the valley bottoms indicate aquifers. The different subcatchments are separated by solid black lines. The three gauging stations that measure the discharge of each subcatchment are indicated by inverted blue triangles. (Schilling et al., 2017)

References

  1. R. V. Blau. Grundlagen für schutz und bewirtschaftung der grundwasser des kantons bern: Hydrogeologie rötenbachtal, wasser-u. Technical report, Energiewirt des Kantons Bern, 1984.
  2. R. V. Blau and F. Muchenberger. Grundlagen für schutz und bewirtschaftung der grundwasser des kantons bern: Nutzungs-, schutz- und Überwachungskonzept für die grundwasserleiter des obersten emmentals, zwischen emmenmatt, langnau und eggiwil. Synthesebericht, 1997.
  3. D. Käser and D. Hunkeler. Contribution of alluvial groundwater to the outflow of mountainous catchments. Water Resources Research, 52(2):680–697, 2016. [ DOI ]
  4. O. S. Schilling, C. Gerber, D. J. Partington, R. Purtschert, M. S. Brennwald, R. Kipfer, D. Hunkeler, and P. Brunner. Advancing physically-based flow simulations of alluvial systems through atmospheric noble gases and the novel 37Ar tracer method. Water Resources Research, 53(12):10465–10490, 2017. [ DOI ]
  5. M. Würsten. GWB – hydrogeologische untersuchungen aeschau: Schlussbericht. Technical report, Zürich, Switzerland: Geotechnisches Institut, 1991.

Data availability

All datasets

To help finding general datasets, predefined database requests have been created and are regularly executed. Results can be downloaded from the links available here:

Water cycle

Boreholes

Stations

KMZ viewer

The viewer below offers a comprehensive site visualization and information on available data such as types, numbers and dates of measurements, locations of sites, wells and stations, as well as data providers information. This interface also provides an overview of available geophysical maps and cross-sections and is accessible without a database account.

To visualize the data in the Google Earth software, you can download the following KMZ file: Emme.kmz

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