Real-time, Continuous Nitrate Monitoring of the Big Sioux River near Sioux Falls, South Dakota

Science Center Objects

Project Period: ongoing
Cooperators: City of Sioux Falls and East Dakota Water Development District
Project Chief: Galen Hoogestraat


In recent years, in-situ nitrate stream monitoring technology has been developed that allows collection and display of real-time nitrate concentration data, similar to the availability of streamflow at USGS streamgages. Current monitoring activities of nitrate in most eastern South Dakota rivers are insufficient for estimation of nitrate loads, because samples are typically collected in monthly intervals or longer. Major nitrate loads can be transported during short-term runoff events that occur outside of routine sampling visits. The data collected from a nitrate monitor will allow for uses such as:

  • calculation of accurate nitrate loads,
  • examination of trends in water-quality conditions as land-use changes evolve,
  • predictive capabilities for downstream water-quality (downstream river intakes), and
  • calibration of contaminant transport models.

Information about continuous nitrate monitoring across the United States is available from the USGS here.


The objective of this project is to continuously measure nitrate plus nitrite concentrations at the Big Sioux River near Dell Rapids (USGS site 06481000). This site is located about 20 river miles upstream from Sioux Falls with no major intervening tributaries. The equipment utilizes a sensor that uses ultraviolet (UV) absorption technology to measure nitrate in-situ. The data are processed and stored on the USGS National Water Information System, available on the internet in near real-time at 15-minute intervals.

Real-time Data

The nitrate data can be accessed at,00060,00010,99133.