Water Quality Monitoring for Missouri National Recreational River (Niobrara River): 2020 Data Report

Rosse, Anine

The Northern Great Plains Inventory and Monitoring Network (NGPN) began monitoring water quality in the Niobrara River at Missouri National Recreational River in 2014, with the assistance of the U.S. Geological Survey (USGS). This report summarizes the data collected during the 2020 ice-free season (March 23 through October 22) for water temperature, dissolved oxygen, specific conductance, and pH. Streamflow is measured year-round. This was the third season of continuous monitoring. 2020 ended up being a very dry year with less than 50% of the yearly average precipitation. However, daily mean discharge peaked at 10,800 cubic feet per second (and maximum instantaneous discharge of 15,500 cfs) on June 9th, considerably lower than the record peak in 2019 of 123,000 cfs, which translated to above average streamflow. Water quality also was measured, including in 2014 which had a peak of 7,670 cfs and 2017 which had a peak of 4,910 cfs. There was considerable seasonal variation in all water quality measures. A summary of our results can be found in the Descriptive Statistics Summary tables for the ice-free season (Table 2) and for each month (Table 3). Water temperature exceeded states standards .23% of the time, while pH exceeded state standards 2.85% of the time. Nebraska Department of Environment and Energy monitors Escherichia coli (E. coli) bacteria in the Niobrara River. E. coli can be a human health concern especially because the Niobrara’s main draw is river recreation. Between 2014 and 2021, bacteria levels exceeded standards for moderately used recreational waters (298 cfu/100 mL) 24 % of the time in reach (NI2-10000) and the geomean standard (126 cfu/100 mL) exceeded standards in 2020. The Niobrara River remains nonsupporting of its recreation use due to E. coli. There is an approved TMDL for E. coli, placing it in category 4a. NGPN’s collaboration with USGS supported real-time and archived access to this data through the USGS National Water Information System Website Niobrara River Near Verdel, Nebr. - USGS Water Data for the Nation where it remains available to the public.