Case study - Buoy-based temperature profiling in the Bavarian Lakes

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Courtesy of The OTT Hydromet Group

In summertime a temperature stratification occurs in deep lakes – the surface water is warm, but deep down the water is cold.  This has considerable influence on the nutrient balance and the biological habitat in these lakes. Due to generally higher air temperatures induced by the climate change, both change and have effects on the life conditions of the ecosystems in the lakes.

Researchers use  OTT buoys and the OTT net DL datalogger to study the long term effects of climate change on the Bavaraian lakes.

Background

  • The Bayerische Landesamt für Umwelt (Bavarian State Office for Environment) cooperated with the WWA Weilheim (Water Managment Authority) and OTT Hydromet (detailed planning, system integration), to implement a measurement project for the continuous monitoring of water temperature in a water profile in the Bavarian Ammersee.
  • As generally approved methods which have been tested already in the long-term were practically non-existent, it was necessary to look for new approaches to realize the customer’s idea of a buoy based temperature profile.
  • With enormous effort a buoy was installed at the deepest point of the Ammersee (81 m ) which is held in position by three concrete weights (750kg each).
  • A measurement chain which is fixed on the underside of the buoy continuously measures the water temperature of the Ammersee at 16 different depths.
  • Meteorological data monitored by the additionally installed compact weather station help to analyse the temperature data delivered by the measurement chain.

Monitoring Solution

  • The measurement buoy is anchored at the deepest point of the lake (81m).
  • At its underside there is a measurement chain with 16 temperature sensors, evenly distributed down the water column right to the bottom of the lake.

Compact weather station for monitoring the meteorological parameters:

  • Air temperature
  • Air pressure
  • Relative humidity
  • Global radiation
  • Wind direction
  • Wind speed

The buoy delivered by OTT Hydromet is equipped with extensive measurement technology:

  • Solar panels for autonomous power supply
  • Measurement chain with 16 temperature sensors
  • Data logger OTT netDL 500 with remote data transmission

More:

  • The temperature sensors of the measurement chain and of the compact weather station are continuously collecting data (average values in 15 minutes intervals).
  • The measured data is stored in the OTT netDL data logger which is installed inside the buoy.
  • Several times a day, the data is transferred via mobile communication from the measurement site to a database of the Water Management Authorities, where they are immediately available for evaluation.

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