Langtjern – long term ecological monitoring
Since 2010, NIVA has built an ecological monitoring site at Langtjern in Buskerud. It opens up a wealth of possibilities in the monitoring of freshwater and climate research.
The ecological monitoring site Langtjern is a forested lake catchment in southeastern Norway at circa 500 to 700m elevation. The catchment has not been disturbed by any direct human interference since early in the 20th century. Therefore, it is well-suited to study natural responses of water chemistry, element cycles and biology to large scale changes in our environment such as deposition of pollutants and climate change.
Langtjern has also been a site for investigation of acid deposition effects on water chemistry and biota since the early 1970's.
Since 2010, infrastructure for climate monitoring was installed in inlet, lake, soils and outlet of the catchments. The monitoring produces high-quality data for validation and calibration of lake- and catchment models.
The monitoring and research projects at Langtjern have provided data for numerous articles and will be a useful resource for researchers in the future.
The Lake Langtjern buoy measures water temperature using a thermocouple at 8 different depths (0.5m, 1m, 1.5 m, 2m, 3m, 4m, 6m, 8m). Oxygen saturation is measured with a Aanderaa Optode 4175 at depths of 1m and 8m.
At the lake outlet temperature is measured in air, water and soil (10 cm) using a thermocouple. pH is measured with a Honeywell Durafet II and conductivity with a Honeywell graphite electrode, both having a direct line transmitter (4-20 mA). Water level is measured with a pressure cell. Coloured dissolved organic matter (CDOM) is measured with a TriOS Microflu-CDOM (ex 370nm/em 460nm) (D, small sensor) and UV-absorption with a TriOS ProPS (190-360 nm) (D, large sensor) with a 1 cm light path. Both have mechanical wipers to remove biofilm. Additionally water flow is measured at the inlet LAE03.
A new weather station was installed at Langtjern in November 2012, replacing a station from 2011. Air temperature and relative humidity is measured using a Campbell Scientific CD215. Global radiation with a Apogee SP-212 sensor. A Young Model 05103-5 measures wind speed and direction. In addition a web camera is installed at the station (Campbell Scientific CC5MPX). A sensor monitoring precipitation (Geonor T-200B) will be installed at the station in the near future
For power generation in this remote area solar panels and a methanol fuel cell have been installed. A small cabin is set up by the outlet to house various instruments.
Lake Langtjern description
Lake Langtjern (60°37’N; 9°73’E) is a small and shallow (lake surface 0.227 km2, mean depth 2 m) humic, acid-sensitive, oligotrophic lake located in central Norway. Langtjern has a small catchment area (4.8 km2, ca. 510-750 m.a.s.l) that is dominated by unproductive pine forest, wetlands and bedrock. Yearly precipitation is 750 mm/yr. Langtjern generally experiences long winters and a stable snowpack.