Southeast Alaska river water quality in 2020: Glacier Bay, Klondike and Sitka

The Southeast Alaska Inventory and Monitoring Network (SEAN) has prioritized continuous water quality monitoring in Glacier Bay National Park and Preserve, Sitka National Historical Park and Klondike Gold Rush National Historical Park since 2010. Water quality is a sensitive indicator of ecosystem health, and the data so far suggest good river health, with episodic exceedances of Alaska Department of Environmental Conservation (ADEC) standards. This page rewrites the network's 2020 annual update.

Sondes are housed in fixed pipes near the riverbank, with underwater sensors measuring five key variables every hour. Image from the National Park Service's page, Glacier Bay.

What is measured

At one fixed site per park, from early spring to late fall, sensors record hourly:

• Water temperature, which follows air temperature and snow or glacial melt.
• Dissolved oxygen, essential to aquatic life and mainly set by temperature.
• pH, a measure of acidity or alkalinity shaped by local rocks, soils and rain.
• Specific conductance: in Southeast Alaska higher values mean groundwater influence, lower values rain and snow runoff.
• Turbidity, tracked only at Klondike, which signals precipitation or glacial runoff.

Readings are judged against ADEC standards for fish: temperature above 13°C, dissolved oxygen below 7 mg/L, and pH below 6.5 or above 8.5 are unsuitable.

The 2020 weather

A robust winter snowpack and frequent precipitation ended several drought years. Rainfall was well above average from June through August, the second wettest summer on record for downtown Juneau according to the Alaska Climate Center. Temperatures stayed close to normal. Park staff visited monthly to check calibration and download data. Glacier Bay lost little data to a brief early-July interval when sensors were out of the water; Sitka and Klondike each had pH sensor problems that left one-month gaps, and a Sitka logging problem left August readings missing.

Salmon River, Glacier Bay

Chart from the National Park Service: Salmon River, 2020 daily means against earlier hourly measurements.

The park has more than 300 streams. The Salmon River is strongly groundwater-fed, drains Excursion Ridge and holds pink, chum and coho salmon, steelhead, cutthroat trout and Dolly Varden. In 2020 temperatures were cooler than normal, and summer exceeded the 13°C standard for only five hours in early August. Dissolved oxygen stayed suitable, pH was stable, and conductance varied far less than usual in spring and summer because of frequent rain. A USGS gage recorded record maximum discharge in February, April, May, June and December and a near-record annual mean.

Taiya River, Klondike Gold Rush

Chart from the National Park Service: Taiya River, 2020 daily means against earlier hourly measurements.

The Taiya drains a mountainous watershed that was, as of 2010, about 29% glacier-covered, and glacial outburst floods have shaped it. Its temperature responds less to air temperature than other sites, and 2020 was near or below normal, reaching freezing in October. Dissolved oxygen was above average and stable. pH sat at the low edge of the historic record, influenced by persistent rain with a natural pH of about 5.3, but never left the ADEC range. Turbidity stayed moderately low and no extreme values were recorded; the late-May start may have missed the spring sediment flush. Spring discharge was elevated but not a record.

Indian River, Sitka

Chart from the National Park Service: Indian River, 2020 daily means against earlier hourly measurements.

The Indian River is the only significant freshwater and estuarine habitat in the park, a low-gradient channel supporting four species of salmon, steelhead, Dolly Varden, rainbow trout, three-spine stickleback and coastrange sculpin. Its steep watershed is over 50% forested and discharge tracks precipitation. In 2020 temperatures stayed below the 13°C standard all season. Dissolved oxygen was well above the threshold all year. pH fell below 6.5 for ten hours in late July and three hours in late October, and a late-summer data gap leaves it unknown whether low pH recurred. The gage set record maximum discharge in February, April, July and November and its highest annual mean.

Sources

• Deborah Goodwin, Courtney Amundson and Thomas Ziomek, National Park Service Southeast Alaska Network, "Southeast Alaska Network water quality monitoring program: 2020 annual update" (https://www.nps.gov/articles/000/sean2020waterquality.htm). The page's data tables are not reproduced; one carried a mislabeled unit; rewritten in hubnx's own words.