Southeast Alaska Rivers in 2019: Drought, Warm Water and Record Low Flows

In 2019 a drought left rivers in Southeast Alaska parks warm, low and short of oxygen, then fall storms pushed flows to records at the other extreme. The Southeast Alaska Inventory and Monitoring Network (SEAN) has tracked river conditions continuously since 2010 in Glacier Bay National Park and Preserve, Sitka National Historical Park and Klondike Gold Rush National Historical Park, and its 2019 annual update says the data suggest good river health with episodic exceedances of Alaska Department of Environmental Conservation (ADEC) standards.

Thousands of salmon return each year to spawn in the Indian River at Sitka National Historical Park. Image from NPS's page.

What is measured

At one fixed site per park, from early spring to late fall, sensors record hourly: water temperature, dissolved oxygen, pH, specific conductance and, at Klondike only, turbidity. Discharge comes from nearby USGS stream gages. Staff visited each site monthly to check calibration and download data. Readings are judged against the state's standards for fish habitat: temperature above 13°C, dissolved oxygen below 7 mg/L, and pH below 6.5 or above 8.5 are unsuitable.

The 2019 weather

After a very dry 2018, the region got less than half its typical snowfall in winter 2019, and precipitation stayed well below normal through spring and summer. Temperatures were among the warmest on record all year. The drought persisted and intensified, and very low streamflow raised water temperatures and lowered dissolved oxygen, both factors in salmon survival and spawning. Fall storms brought near-normal precipitation and eased the drought at low elevations.

Salmon River, Glacier Bay

This groundwater-fed river drains wetlands and forest east of Excursion Ridge and supports pink, chum and coho salmon, steelhead, cutthroat trout and Dolly Varden.

Chart from the Southeast Alaska Inventory and Monitoring Network: daily means for the Salmon River in 2019 against earlier hourly readings, with discharge and precipitation below.

• Temperature stayed at the upper limit of the historic record in spring and summer but never passed the 13°C standard; the May to October mean was 0.72°C above the 2010–2018 mean.
• Dissolved oxygen fell steadily from May to July, reaching the low end of the record, but stayed above 7 mg/L all year.
• pH was stable and higher than much of the record, and always in the optimal range even when two fall storms made it drop sharply.
• Discharge was very low from May to mid-September. July and August set record minimums and October set the record maximum.
• Sensors were out of the water during extremely low water in July and August, which left data gaps.

Taiya River, Klondike Gold Rush

The Taiya, west of Skagway, drains a mountain watershed that was about 29% glacier-covered as of 2010, with the ice retreating. It supports chum, pink and coho salmon and Dolly Varden. A datalogger error lost all the spring readings.

Chart from the Southeast Alaska Inventory and Monitoring Network: daily means for the Taiya River in 2019.

• Temperature responds less to air temperature than at other sites, but was often near the top of the historic range; the May to October mean was 0.24°C above the 2010–2018 mean.
• Dissolved oxygen stayed above 7 mg/L, was stable through summer and rose above the record in the fall.
• pH varied more than usual but stayed in the normal range, as the river buffers storm effects well.
• Turbidity was lower than typical for most of the season, with one storm spike in September and above-average levels in late June and early July during a strong meltwater pulse.
• Discharge stayed high from June to August on melt, since little rain fell, with storm peaks in September.

Indian River, Sitka

Sitka's Indian River holds the park's only significant freshwater and estuarine habitat: a 1-km channel with four salmon species, steelhead, Dolly Varden, rainbow trout, three-spine stickleback and coastrange sculpin. Its small, steep watershed is over 50% forest and its flow follows rain closely.

Chart from the Southeast Alaska Inventory and Monitoring Network: daily means for the Indian River in 2019.

Calibration and datalogger problems left measurements for less than half the sampling season, so temperature was not compared with the long-term mean and the peak summer readings are missing. Oxygen stayed well above 7 mg/L, with record-high fall levels; pH stayed in the optimal range at the upper edge of the record. July set a record minimum discharge and August came close.

Sources

• National Park Service, Southeast Alaska Inventory and Monitoring Network, "Water Quality Monitoring, 2019 Annual Update" (Goodwin, Amundson and Ziomek, 2021, National Park Service, Juneau), at https://www.nps.gov/articles/000/sean2019waterquality.htm; rewritten in hubnx's own words.