Switzerland - Thur Catchment

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Institution

Eawag, Überlandstr. 133, CH-8600 Dübendorf, Switzerland

Name of site

River Thur (1730 km2), NE Switzerland, and RECORD research site at Neunforn (http://www.cces.ethz.ch/projects/nature/Record)

Location

The River Thur is located in NE Switzerland, draining the front ranges of the Swiss NE Limestone Alps (south of the Bodensee basin). It is a tributary of the R. Rhine which flows into the North Sea. 

Geology

The Thur catchment is a mainly Limestone dominated alpine headwater, whereas the pre-alpine lowlands are dominated by ‘Molasse’-Sandstones and Pleistocene unconsolidated sediments.

It is a primarily rural catchment with agricultural activity focussing on the lowlands and scattered settlements. St. Gallen (72,000 inhabitants) and Frauenfeld (23,000 inhabitants) are the largest towns in the Thur catchment.

Hydrogeology

The primary aquifer (Thur valley aquifer) is mainly sand and gravel. It is connected to the Thur river and mostly unconfined. The depth to the water table varies very much in the entire catchment. This information can be given upon request.

The water table at the RECORD field site Neunforn is mainly shallow (see information below). Supporting data are also available, for example geological or hydrogeological maps. The Thur valley aquifer is shown below.

Hydrology

The R. Thur is the largest Swiss river without a natural or artificial reservoir and exhibits fluctuations in discharge and water table similar to unregulated alpine rivers (low discharge: 3 m3s-1; annual mean discharge: 23.3 - 76.4 m3s-1; peak flows up to 1100 m3s-1). Snowmelt and strong rainfall events in the pre-alpine headwaters cause short but rapid increase of discharge.

During base flow outflows of sewage treatment plants are significant contributions. Due to flood protection in the 1980s, the river was straightened and confined to a narrow channel surrounded by 50 – 150 m wide overbanks defined by a levee, behind which a side channel was installed to capture discharge from tributaries and drain agricultural land.

In recent years river restoration measures were established with the aim to improve flood protection and the ecological status of the river and the riparian zone.

Monitoring infrastructure at the RECORD site Neunforn

The activities focus on the R. Thur, the largest river in Switzerland without a natural or artificial reservoir. The revitalisation of the R. Thur is one of the largest ongoing projects in Switzerland.

The monitoring objective is to improve the mechanistic understanding of coupled hydrological and ecological processes in near-river corridors. For this purpose, the following was accomplished:

  • Instrumentation of a restored and a channelized section of the R. Thur as large-scale field experimental site, where we quantify how the relevant variables influence (ground)water quality, ecosystem functioning and biodiversity (see below)
  • Performing controlled experiments at the field site and in the lab
  • Developing process-based models of coupled hydrological, biogeochemical and ecological processes, facilitating transfer to other river systems undergoing restoration.

Agricultural impacts and pollutant types

The main field site is the restored Thur section at Neunforn (Canton Thurgau) and Altikon (Canton Zurich). The main foci are to:

  • Observe the dynamics of hydraulics, morphology and vegetation by automated cameras
  • Assess the distribution of sediments and their associated properties by multiple geophysical surveys
  • Install well transects to identify the origin, travel time and chemical composition of alluvial groundwater
  • Analyze oxygen, carbon, and nutrient cycling along flow paths
  • Perform ecological surveys
  • Monitor the root zone in various vegetation patches
  • Measure agricultural contaminants including nitrate and phosphate
  • Measure hydrological (e.g. water table, soil moisture, sap flow) and meteorological quantities

Available data

Several administrative and research organisations actively support monitoring and evaluation of data within the Thur catchment. The Office for the Environment (Amt für Umwelt) Thurgau and the Office for Water, Waste and Energy (Amt für Wasser, Abfall und Energie) Zurich are monitoring the Thur catchment. The records go back until the 1870s. Both organisations established close collaborations with Eawag and the ETH Zurich. All demonstrate a strong commitment to the observatory.

In addition, data are available online through the Swiss Federal Office of the Environment (FOEN) and the Swiss governmental monitoring network (Meteoschweiz). The Niederneunforn, Widen and Rietholzbach sites are also part of Eawag’s commitment to climate change and pre-alpine catchment research.

Rainfall data are measured at 41 stations in the Thur catchment by Meteoschweiz (governmental monitoring network), plus additional research stations at specific sites, some of them providing online access. Several climate stations in the Thur valley are operated by the canton Thurgau, where data are available, plus additional weather stations at the RECORD and Rietholzbach sites.

Flow data are measured at the catchment outlet and at a network of additional stations by the FOEN. Monthly and daily flow and information on flow peaks are available online; higher resolution data (15 min) is available upon request. These sites and the period of record are shown below.

Relevant publications

  • Chittoor Viswanathan, V., Jiang, Y., Berg, M., Hunkeler, D., Schirmer, M. 2016. An integrated spatial snap-shot monitoring method for identifying seasonal changes and spatial changes in surface water quality. Journal of Hydrology, 539, 567–576.
  • Chittoor Viswanathan, V., Schirmer, M. 2015. Water quality deterioration as a driver for river restoration: a review of case studies from Asia, Europe and North America. Environmental Earth Sciences, 74, 3145–3158.
  • Chittoor Viswanathan, V., Molson, J., Schirmer, M. 2015. Does river restoration affect diurnal and seasonal changes to surface water quality? A study along the Thur River, Switzerland. Science of the Total Environment, 532, 91-102.
  • Doulatyari, B., Betterle, A., Basso, S., Biswal, B., Schirmer, M., Botter, G. (2015). Predicting streamflow distributions and flow duration curves from landscape and climate. Advances in Water Resources, 83, 285–298.
  • Basso, S., Frascati, A., Marani, M., Schirmer, M., Botter, G. (2015). Climatic and landscape controls on effective discharge. Geophysical Research Letters, 42, 8441-8447.
  • von Freyberg, J., Rao, P.S.C., Radny, D., Schirmer, M. (2015). The impact of hillslope groundwater dynamics and landscape functioning in event-flow generation: a field study in the Rietholzbach catchment, Switzerland. Hydrogeology Journal, 23, 935-948.
  • Schirmer, M., Luster, J., Linde, N., Perona, P., Mitchell, E.A.D., Barry, D.A., Hollender, J., Cirpka, O.A., Schneider, P., Vogt, T., Radny, D., Durisch-Kaiser, E. (2014). Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration – The Thur River case study. Hydrology and Earth System Sciences, 18, 1-14.
  • Diem, S., Cirpka, O.A., Schirmer, M. (2013). Modeling the dynamics of oxygen consumption upon riverbank filtration by a stochastic-convective approach. Journal of Hydrology 505, 352–363.
  • Hayashi, M., Vogt, T., Mächler, L. Schirmer, M. (2012). Diurnal fluctuations of electrical conductivity in a pre-alpine river: Effects of photosynthesis and groundwater exchange. Journal of Hydrology 450–451, 93–104.
  • Schneider, P., Vogt, T., Schirmer, M., Doetsch, J. A., Linde, N., Pasquale, N., Perona, P., Cirpka, O. A. (2011). Towards improved instrumentation for assessing river-groundwater interactions in a restored river corridor. Hydrology and Earth System Sciences, 15, 2531-2549.

Research opportunities and additional information

Research activity and outputs

  • Quantification of river water - groundwater interaction (RECORD)
  • Nutrient turnover and degradation of micro pollutants during bank filtration (RECORD)
  • Sediment and vegetation dynamics (RECORD)
  • Effects of Environmental heterogeneity on ecosystem functioning and biodiversity
  • Atmosphere - soil moisture climate feedback at Rietholzbach (SMEX)
  • New 2D groundwater model for Thurtal aquifer finished in 2008 (Simultec)
  • Fate and transport model of micropollutants at the surface water / groundwater interface

Related information

Field sites main page