Water Quality Monitoring for Niobrara National Scenic River: 2020 Data Report

Rosse, Anine

The Northern Great Plains Inventory and Monitoring Network (NGPN) began monitoring water quality in the Niobrara River at Niobrara National Scenic 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 (April 8 through October 26) 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 moderately wet year after a record wet year in 2019 with daily mean discharge peaking at 1,810 cubic feet per second (and maximum instantaneous discharge of 1,890 cfs) on March 31st, considerably lower than the record peak in 2019 of 6,970 cfs. Flow was comparable to the other years. Water quality was measured including in 2014 which had a peak of 2,930 cfs, and 2017 which had a peak of 1,870 cfs. Discharge in 2020 still remained above the median for the period of record, 795 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). Measured parameters are well within state standards with just one dissolved oxygen measurement falling below the state standard of 5.0 mg/L in 2020. In comparison, 2017 produced some minor high pH exceedances but there were no violations in 2014. The state of Nebraska and the National Park Service (NPS) monitor Escherichia coli (E. coli) bacteria in the 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) 3-57 % of the time in the lower reach (NI3-10000) and the geomean standard (126 cfu/100 mL) exceeded standards in 2020. The upper reach (NI3-20000) does not violate state water quality standards though E. coli remains an important issue in NIOB. 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 Sparks, Nebr. - USGS Water Data for the Nation where it remains available to the public.