Sensor stations are installed into the water at all NEON aquatic field sites to collect automated measurements of physical and chemical properties of aquatic water bodies. Measurements are collected many times per hour capturing patterns in how aquatic bodies change in response to weather patterns and hydrologic drivers. The placement of sensor stations and data collected varies slightly between stream, river and lake sites. Meteorological stations and groundwater wells are also installed near these surface water sensors to allow direct integration and extrapolation between suites of measurements.
Placement of Sensors by Site Type
In the schematics below, the surface water sensors are the yellow icons called "Sensor Stations."
At stream sites, two sensor stations are installed a maximum of 400 m from each other within the sampling reach of the site. The precise placement of each station is based on hydrologic characteristics, i.e., discharge and velocity values, measured at each location enabling consistent travel times between the two sensor sets. These stations collect surface water chemical and physical properties data.
At non-wadeable river sites, one sensor station is installed near the shore of the river to collect photosynthetically active radiation (PAR) and surface water elevation. A buoy-mounted sensor station is placed deeper in the basin, but outside of the main navigational channel, to collect chemical and physical properties of surface water and at multiple depths.
At lake sites, one sensor set is placed near the inlet of the lake and another near the outlet of the lake to collect measure Photosynthetically active radiation (PAR) and surface water elevation. A buoy-mounted sensor station is placed in the deepest location of the main basin to collect chemical and physical properties of surface water and at multiple depths.
Comparison of Aquatic Instrument System (AIS) Measurements by Aquatic Site Type
Additional surface water samples are collected by field scientists on a semi-annual basis as part of NEON's Aquatic Observations System (AOS).
Additional Instrument Measurements
NEON’s aquatic field sites are also outfitted with automated instruments that collect meteorology, phenology and groundwater data. A staff gauge is also installed at each aquatic site to measure changes in water height (or gauge height).
Surface Water Related Data Products
- Elevation of surface water
- Nitrate in surface water
- Photosynthetically active radiation below water surface
- Stream discharge
- Stream discharge rating curve
- Surface water data
- Temperature (PRT) in surface water
- Temperature at specific depth in surface water
- Water quality
Sensor-specific details may be found in the data product documentation on the NEON data portal.
Why These Measurements?
PAR is defined as radiation within the range of 400 nm to 700 nm. Radiation within this range drives photosynthesis, the process by which autotrophs (e.g., plants and algae) convert carbon dioxide and water into glucose and oxygen. Photosynthesis is critical to aerobic life on earth and many chemical, physical and biological processes, including the global carbon cycle.
Surface water elevation can be linked to the quantity of water flowing through a stream or river or the volume of water in a lake and is a critical physical parameter in aquatic ecology. Stream discharge is controlled by several hydrologic components as well as physical characteristics of the watershed and it is considered a master variable of the hydrological cycle at the landscape scale and therefore critical to understanding how water moves through the environment. This is necessary to determining how both aquatic and terrestrial ecosystems respond to hydrologic changes.
Water temperature profiles indicate whether or not the lake or river is thermally stratified, where the body of water is separated into two or more layers based on temperature. Typically, in a thermally stratified system, the top layer of water is warmer (epilimnion) while the lower layer is colder (hypolimnion). The area separating the two layers is known as the thermocline or metalimnion. Water chemistry and aquatic communities are highly dependent on water temperature and thermal stratification can dramatically change the water chemistry and biology of each layer.
Additional water quality parameters, including specific conductance, pH, chlorophyll a, dissolved oxygen, turbidity, nitrate, and fluorescent dissolved organic matter are related to a variety of biogeochemical processes important to surface water ecosystems. The water quality measurements NEON collects include both physical and chemical properties that are indicative of the changing health of aquatic ecosystems. These data may also be used to base metabolism model estimates on. At lake and river sites, information is collected from multiple depths if the water body is at least 2 m deep in order to understand the changes in water quality through the vertical water column. In small streams, however, there are sensor stations are deployed longitudinally to capture the variation in water quality from upstream to downstream.
Nitrate measurements in aquatic systems are critical to understanding the biogeochemical cycle and mechanisms in the ecosystem. Changes in the concentration of nitrate over time may be an indication of shifts in the trophic structure and community composition of the aquatic ecosystem.