EXECUTIVE SUMMARY – In 2016, The Upper Missouri Watershed Alliance (hereafter referred to as UMOWA) began collecting water quality data at seven sites on the Upper Missouri River between Wolf Creek and Cascade. These sites were chosen to coincide with preexisting sites that were established for the sampling of macroinvertebrates by Montana Biological Survey in 2015. This was the second year that water quality samples were collected. Samples were collected in July and October of 2017. High water during the spring of 2017 prevented the collection of April samples.

In 2016, samples were analyzed for recoverable metals. In 2017, this analysis was eliminated for financial reasons and because these materials were recovered at very low levels in 2016 suggesting that under current conditions, they pose no immediate threat to the Missouri River.

The water quality data collected in 2017 reinforced the seasonal and spatial trends observed in 2016 and allowed a year-to-year comparison between 2016 and 2017.

Overall, nutrient concentrations were higher in 2017 than 2016. The increase was most apparent during October. During October of 2017, five sites (LPPC US, Craig, Dearborn US, Dearborn DS, and Hardy Creek) exceeded the recommended screening value for inorganic nitrogen concentrations, the numeric nutrient standard for total nitrogen, and (with the addition of the Cascade site) the numeric nutrient standard for total phosphorus. In 2016, no sites during any season exceeded the numeric nutrient standards or screening values set by the Montana Department of Environmental Quality (hereafter referred to as MDEQ).

Therefore, during the fall period of 2017, nutrient levels within the Missouri River exceeded the recommended levels set by MDEQ. This is cause for concern. It is possible that high nutrient levels are the biggest threat that the Upper Missouri River is facing at present. It is critical that UMOWA continue to monitor water quality in 2018 to see if nutrient concentrations remain at threatening levels.