Madison River Water Quality and Flow near West Yellowstone, Montana, in 2022

Looking upstream from the sampling site near West Yellowstone, March 2022. NPS.

The river

The Madison River begins inside Yellowstone National Park at Madison Junction, where the Firehole and Gibbon rivers meet — both warmed by geothermal features. It runs 19 miles (31 km) through the park, crosses the boundary into Hebgen Lake, heads toward Ennis, Montana, and continues northwest to join the Jefferson and Gallatin rivers, forming the Missouri River. It's a renowned place for fishing, birding and wildlife watching.

The Park Service's Greater Yellowstone Inventory and Monitoring Network samples it each year at a Montana Highway 191 bridge, just outside the park and 3.75 miles (6 km) north of West Yellowstone.

Figure 1. The watershed above the monitoring site. NPS.

Figure 2. The sampling site (yellow star) and the USGS gage (circle), 4.5 miles (7 km) upstream. NPS graphic on a USDA base map.

Flow

The U.S. Geological Survey gage near West Yellowstone (USGS 06037500) has daily flows back to 1913, with a gap from 1975 through 1983, and daily water temperatures since 2014. Its hydrograph is typical of a groundwater-fed river.

• Despite Yellowstone's record flood in June 2022, the year's average daily flow was 427 cubic feet per second (cfs), below the 1924–2021 average of 486 cfs. Flows fell below average by the end of June (day 175).
• Peak: 2,140 cfs on 13 June (day 164), the day of the flood. The record is 2,750 cfs, in 1996; the long-term average peak is 1,306 cfs, on 24 May (day 144).
• Low: 311 cfs, against a long-term average annual minimum of 335 cfs.

Figure 3. Daily discharge at USGS 06037500, 2022 against the 1924–2021 record. NPS.

Water quality

The water is high quality, shaped by geology: many of Yellowstone's geyser basins drain into the Firehole, and that geothermal water can push temperature, pH and arsenic past state criteria.

The network sampled nine times from March to October 2022.

• Nutrients were low. Ammonia was below detection every time (reporting limit 0.05 mg/L); nitrate + nitrite was 0.01–0.04 mg/L or undetected.
• Total suspended solids ranged from 2 to 9 mg/L or were undetected.
• Arsenic: total arsenic exceeded Montana's chronic aquatic life criterion of 0.15 mg/L on every sampling date. Since water inside the park is shaped by geothermal features, it's likely natural.

Figure 4. Total arsenic (yellow circles) against flow and Montana's standard (black line), 2022. NPS.

Temperature and fishing closures

• 2022 ran warmer, and warmed earlier, than the 2014–2021 record.
• The daily maximum peaked at 26.8°C (80.2°F), against a 2014–2021 average of 25.9°C (78.6°F).
• Montana Fish, Wildlife and Parks can close cold-water fishing when the water tops 73.0°F (22.8°C) at any time of day for three days in a row (Rule 12.5.507), or when flows drop below minimum levels. In 2022 the river first passed that mark on 2 July (day 183) and stayed above it on consecutive days through the end of August. Geothermal inflow is part of the reason.

Figure 5. Daily average water temperature, 2022 against 2014–2021. NPS.

Figure 6. Daily maximum water temperature and the closure threshold (dashed line). NPS.

2022 results

Lab results (mg/L), analysed by Energy Laboratories in Billings, Montana. "< x" is the reporting limit — the lowest value a lab reports; the substance may be there below it. Rep is a replicate sample. Field blanks were below detection.

Field results, from a YSI EXO1 sonde; each value is the average of four readings across the river.

All years' data are in the NPS DataStore, and on the Water Quality Portal under site ID 11NPSWRD_WQX-YELL_MDR (in the "Advanced" menu).

How it's measured

Sampling from the bridge with a bridge-board, reel and DH-95 suspension sampler, used when the river is too deep to wade. NPS.

• Water samples, taken monthly while the river is ice-free, follow the USGS National Field Manual and are depth- and width-integrated: water is drawn through the full depth at several points across the river.
• • Wadeable: a 1 L hand-held DH-81 sampler on a 1 m wading rod.
  • Too deep to wade: from the bridge, with a bridge-board or crane, a reel and a DH-95 suspension sampler.
  • Water goes into an 8 L churn splitter, which mixes it and dispenses a representative subsample into lab bottles, shipped overnight to an EPA-certified commercial lab.
• Core parameters — temperature, specific conductance, dissolved oxygen, pH and turbidity — are read in the river with a hand-held multi-parameter instrument at four points across it, under the network's regulatory water quality protocol.
• Flow and temperature come from the USGS gage, published on the National Water Information System.

The full protocols are in NPS DataStore Collection 7853.

Reading core water quality with a hand-held instrument, here on the Lamar River, Wyoming. NPS.

The standards it's held to

Under the Clean Water Act, Yellowstone's surface waters are Outstanding National Resource Waters; Montana classes waters wholly inside national parks as A-1, Outstanding Resource Waters (ARM 17.30.617). Once it leaves the park near West Yellowstone, the Madison is classed B-1: suitable for drinking after conventional treatment, swimming and other full-contact recreation, salmonid fish and other aquatic life, waterfowl and furbearers, and farm and industrial supply.

Results are compared against:

• EPA National Recommended Water Quality Criteria, and the EPA's Quality Criteria for Water 1986 (the "Gold Book");
• Montana's numeric standards, Circular DEQ-7, and the state's 2020 Water Quality Integrated Report;
• the Madison nutrient, E. coli and metal TMDLs and water quality improvement plan.

Looking downstream from the sampling site, May 2022. NPS.

Earlier years: Madison River monitoring, 2021.

Sources

Based on "Water Resources Monitoring in the Madison River near West Yellowstone, Montana, 2022," by the Greater Yellowstone Inventory and Monitoring Network (2024), Yellowstone National Park, National Park Service, including its two downloadable data tables; a work of the United States government in the public domain. The source's field table gives conductivity in µS/m; values of this size are µS/cm, and are labelled so here.