Water Quality in the Yellowstone River at Corwin Springs, Montana

The Yellowstone River has relatively high water quality and much of the watershed upstream from the monitoring location is managed within federal lands. We sampled the Yellowstone River for water chemistry and core water quality parameters eight times from April to November in 2021. Core water quality parameters include temperature, specific conductance, dissolved oxygen, pH, and turbidity.

Water chemistry contained low levels of dissolved nutrients. Ammonia as nitrogen (NH₃ as N) was below detection levels on all sampling dates except on 8 April and 18 November 2021 when concentrations of 0.07 mg/L and 0.06 mg/L were detected, respectively (reporting limit is 0.05 mg/L). Nitrate + nitrite as nitrogen (NO₃ + NO₂ as N) levels were between 0.03 and 0.22 mg/L and averaged 0.13 mg/L across all sample dates (reporting limit is 0.01 mg/L). Total suspended solids (TSS) and total phosphorus (P) concentrations tended to be higher with higher flows. Except for a spike in TSS on the 18 November 2021 sampling date, TSS and total P concentrations were at their annual maxima during the 14 June 2021 sampling event.

Daily discharge (in cfs; solid line) in the Yellowstone River at Corwin Springs, MT (USGS Gage 06191500), in 2021 shown with concentrations of total suspended solids (circles) summarized from water collected during 2021 monthly sampling.

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Daily discharge (in cfs; solid line) in the Yellowstone River at Corwin Springs, MT (USGS Gage 06191500), in 2021 shown with concentrations of total phosphorus (circles) summarized from water collected during 2021 monthly sampling.

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Trace metals (such as arsenic, zinc, mercury, and lead) have been detected and are often naturally present at measurable concentrations in Yellowstone National Park waters (Elliott and Hektner 2000). Total arsenic concentrations tended to be lower with higher flows. In 2021, total arsenic levels in the Yellowstone River at Corwin Springs did not exceed the Montana chronic aquatic life criteria (0.15 mg/L) but did exceed human health surface water standards (0.010 mg/L). Due to arsenic naturally originating in Yellowstone National Park (Planer-Friedrich et al. 2007), Montana DEQ has determined a separate annual median nonanthropogenic arsenic standard for the Yellowstone River. On the segment of the Yellowstone River from the Montana/Wyoming border to Mill Creek, in which the Corwin Springs sampling location is montored, this standard is 0.028 mg/L (MTDEQ 2019a, b; MTDEQ 2020).

Daily discharge (in cfs; solid line) in the Yellowstone River at Corwin Springs, MT (USGS Gage 06191500), in 2021 shown with concentrations of total arsenic (circles) summarized from water collected during 2021 monthly sampling. The black dotted line is the MTDEQ nonanthropogenic annual mean flow criterion (0.028 mg/L). MTDEQ aquatic life chronic criterion is the solid black line (0.15 mg/L). The black dashed line is the MTDEQ human health surface water criterion (0.010 mg/L).

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Water temperature is monitored continuously by the USGS at the Corwin Springs station (USGS Gage 06191500). Daily water temperature averages in 2021 were higher and these warmer temperatures occurred earlier than average daily water temperatures in the previous five years (2016–2020). In 2021, daily maximum water temperatures were above the daily maximum water temperatures from 2016–2020. The maximum daily water temperature reached in 2021 (22.3°C) was also above the average daily maximum water temperature from 2016–2020 (20.6°C).

Montana Fish, Wildlife and Parks regulates cold water fishing closures when water temperatures exceed 73.0°F (22.8°C) at any time of the day for three consecutive days (Montana Rule 12.5.507). The maximum temperature recorded in 2021 at the Corwin Springs station was 22.3°C on 1 August (day 213 of the year).

Summary of the average daily water temperature in the Yellowstone River at Corwin Springs, MT (USGS Gage 06191500), in 2021 and for 2016–2020.

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Summary of the daily maximum water temperature in the Yellowstone River at Corwin Springs (USGS Gage 06191500) in 2021 and from 2016–2020. Current Montana Fish, Wildlife & Parks drought policy states that angling closures may be enacted to protect cold-water fish species when daily maximum water temperatures reach at least 73°F (22.8°C; represented by the dashed line) for three consecutive days or when flows drop below minimum levels.

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2021 Water Quality Lab Results

The following two tables contain 2021 water quality lab results for the Yellowstone River at Corwin Springs, MT, from April through July and August through November, respectively. Download tabular data here for these tables.

Table 1. April through July, 2021, monthly water chemistry lab results (in mg/L) for the Yellowstone River at Corwin Springs, MT. All samples were processed at Energy Laboratories in Billings, MT. Reporting limit (in mg/L) is the threshold value that many analytical labs consider to be the lowest reportable value for an individual analyte; this value may be higher than the maximum detection limit. 
ND = non-detectable result. Some sampling events included a replicate or blank sample where indicated; blank samples are processed using certified inorganic free deionized water.

Monthly water quality lab results, April to July for the Yellowstone River, MT

Water Chemistry Lab Parameters (Yellowstone River at Corwin Springs, MT)	Reporting Limit	8-Apr	8-Apr Replicate Sample	12-May	12-May Blank Sample	14-Jun	27-Jul

Table 2. August through November 2021 monthly water chemistry lab results (in mg/L) for the Yellowstone River at Corwin Springs, MT. All samples were processed at Energy Laboratories in Billings, MT. Reporting limit (in mg/L) is the threshold value that many analytical labs consider to be the lowest reportable value for an individual analyte; this value may be higher than the maximum detection limit. ND = non-detectable result. Some sampling events included a replicate or blank sample where indicated; blank samples are processed using certified inorganic free deionized water. 

August to November monthly water quality results.

Water Chemistry Lab Parameters (Yellowstone River at Corwin Springs, MT)	Reporting Limit	17-Aug	17-Aug Blank Sample	7-Sep	3-Nov	18-Nov

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2021 Water Quality Field Results

Download tabular data here for this table.

Table 3. Monthly water quality field parameter results for the Yellowstone River at Corwin Springs, MT.

Monthly water quality field results for the Yellowstone River at Corwin Springs, MT.

Water Quality Field Parameters (Yellowstone River at Corwin Springs, MT)	8-Apr	12-May	14-Jun	27-Jul	17-Aug	7-Sep	3-Nov	18-Nov

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More Data

Data prior to 2021 are available at the Water Quality Portal using YELLWQ01 for the project and WQX-YELL_YS549.7M as the site identifier for the Yellowstone River at Corsin Springs, MT.

Citations

Elliott, C. R., and M. M. Hektner. 2000. Wetland resources of Yellowstone National Park. Yellowstone National Park, Mammoth, Wyoming.

Montana Department of Environmental Quality (MTDEQ). 2019a. Demonstration of nonanthropogenic arsenic levels: Yellowstone River, Montana. Helena, MT: Montana Dept. of Environmental Quality

Montana Department of Environmental Quality (MTDEQ). 2019b. Derivation of the nonanthropogenic arsenic standards for segments of the upper and middle Yellowstone River. Helena, MT: Montana Dept. of Environmental Quality.

Montana Department of Environmental Quality (MTDEQ). 2020. Addendum to derivation of the nonanthropogenic standards for segments of the upper and middle Yellowstone River. Helena, MT: Montana Dept. of Environmental Quality.

Planer-Friedrich, B., J. London, R. B. McCleskey, D. K. Nordstrom, and D. Wallschläger. 2007. Thioarsenates in geothermal waters of Yellowstone National Park: Determination, preservation, and geochemical importance. Environmental Science & Technology 41:5245–5251.

Article created by the NPS Greater Yellowstone Inventory and Monitoring Network.