Water Quality Monitoring, 2019 Annual Update

Thousands of salmon return annually to spawn in the Indian River at Sitka National Historical Park.

Water quality is an important and sensitive indicator of aquatic and terrestrial ecosystem health. Monitoring river and stream conditions helps scientists and park managers detect environmental patterns driven by human activity, climate change and watershed dynamics, then use that information to make better-informed decisions. 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. Data collected thus far suggest good river health with episodic exceedances of Alaska Department of Environmental Conservation (ADEC) water quality standards.

This research program (1) tracks hourly conditions at a single fixed site in each park from early spring to late fall, (2) examines seasonal and interannual variability, and (3) evaluates observations against state standards indicating optimal or hazardous conditions for fishes. Continuously collected data include:

• Water temperature (°C) reflects air temperature patterns and snow or glacial melt.
• Dissolved oxygen concentration (mg/L) quantifies microscopic oxygen bubbles essential to aquatic organisms. Mainly regulated by temperature, oxygen fluctuations can also be caused by enhanced biological respiration or decomposition, and water aeration.
• pH is a unit-less measure of hydrogen ion concentration indicating relative acidity or alkalinity. It affects freshwater species and many biogeochemical processes. The chemistry of local rocks, soils, and rain impact observed pH levels.
• Specific conductance (mS/cm) describes the ability of water to conduct an electrical current. In Southeast Alaska, higher values represent groundwater influence and lower values rain and snow runoff.
• Turbidity (NTU) measures water clarity due to sediment load; increases in turbidity typically signal precipitation events or glacial runoff, thus this metric is tracked at Klondike Gold Rush National Historical Park only.

2019 Southeast Alaska Weather Conditions

After a very dry 2018, the region received less than half its typical snowfall during winter 2019 and precipitation levels well below normal continued through spring and summer. Year-round, 2019 temperatures were among the warmest on record, 1.6-5°F (0.6-2.8°C) above average each month (Alaska Climate Center). The ongoing drought persisted and intensified. Among many impacts, extremely low streamflow raised water temperatures while reducing dissolved oxygen concentrations, factors influential to salmon survival and spawning success. During the fall, a series of storms brought near normal precipitation, reducing drought impacts at low elevations; longer term ecosystem effects require more rainfall and mountain snowpack to recover.

Methods

During the ice-free season, water quality sondes sampled each river hourly at fixed locations. Once a month, park staff visited the site to check sensor calibrations, download data, and resolve any problems; this monitoring project would not be possible without their dedication and assistance. At Glacier Bay, sensors were not submerged during intervals of extremely low water in July and August resulting in data gaps, while a datalogger error in Klondike lost all spring readings. Sitka measurements are available for less than half of the sampling season because of calibration and datalogger issues. SEAN’s certified annual water quality data are publicly available, as is the peer-reviewed protocol guiding this monitoring program.

Daily mean water quality parameters for the Salmon River in 2019 (black lines) relative to the hourly measurements prior to 2019 (purple points). Bottom panel shows daily mean discharge rates (black lines) from the nearby stream gage and precipitation (purple bars) from the closest weather station.

Shaded regions denote ADEC thresholds for unsuitable fish habitat for temperature (above 13°C), dissolved oxygen (below 7 mg/L), and pH (below 6.5 or above 8.5).

Glacier Bay National Park and Preserve

Glacier Bay National Park and Preserve has more than 300 streams flowing over 3,380 km through a diversity of glacially shaped landscapes. The SEAN monitors the Salmon River, whose watershed primarily drains Excursion Ridge to the east and features mature wetlands and forests. This system is strongly groundwater influenced, reflecting greater transport and storage capacity in wetlands and the local aquifer. The sonde is located at river km 9.0, just upstream from the park boundary (map). Since 2014, a U.S. Geological Survey (USGS) streamflow gage has operated about one km downstream from the monitoring site; no significant tributaries exist between the two stations.

The Salmon River is home to many productive anadromous fish populations, such as pink, chum, and coho salmon, steelhead, cutthroat trout, and Dolly Varden. Although their life histories vary, especially with respect to spawning location and amount of time spent in the stream, all are vulnerable to environmental shifts due to climate processes. Tracking temporal changes in water temperature and flow patterns offers insight to these risks and is an established focus for Glacier Bay National Park and Preserve.

2019 Observations

• Water temperature followed a typical seasonal pattern, though several very abrupt drops mid-fall occurred with passing weather systems. Observations remained at the upper limit of the historic record during spring and summer, but peak conditions did not exceed the 13°C ADEC standard. Mean temperature 1 May - 31 October was above the 2010-2018 mean by 0.72°C.
• Dissolved oxygen dropped steadily May through July during the intensifying drought, improving in pulses during brief summer rain events. Levels rose in the fall, returning to near normal for the Salmon River. Concentrations of dissolved oxygen remained above the ADEC threshold of 7 mg/L all year, despite reaching the low end of the historic record mid-summer.
• pH was stable and higher than much of the long-term record throughout all months. Sharp drops in pH occurred during two fall storms but values were always within optimal range (6.5-8.5).
• Specific conductance was higher compared to other sites, reflecting increased ion levels from wetlands and developed soils. It was also more variable, with brief, steep declines during rain events. Groundwater influence dominated during the ongoing dry period, with spring and summer 2019 capturing some of the highest conductance values to date.
• Discharge was very low from May to mid-September, reflecting regional drought conditions, then rose substantially with a series of fall storm events. For the Salmon River gaging station, July and August 2019 set record minimum discharge levels while October set the record maximum.

Salmon River freshwater data summary, 2019.

Parameter	n	Median	Mean	SD	Min	Max
Temperature (ºC)	4,395	7.76	7.55	2.35	1.98	12.74
DO concentration (mg/L)	4,394	10.52	10.48	1.10	7.81	13.76
pH	4,394	7.88	7.87	0.12	7.04	8.18
Specific conductance (mS/cm)	4,395	0.22	0.22	0.07	0.01	0.36
Discharge (NTU)	5,209	101.95	184.87	224.51	24.45	1,462.28

Daily mean water quality parameters for the Taiya River in 2019 (black lines) relative to the hourly measurements prior to 2019 (purple points). Bottom panel shows daily mean discharge rates (black lines) from the nearby stream gage and precipitation (purple bars) from the closest weather station.

Shaded regions denote ADEC thresholds for unsuitable fish habitat for pH (below 6.5 or above 8.5); Taiya River observations have not approached temperature (above 13°C) or dissolved oxygen (below 7 mg/L) thresholds.

Klondike Gold Rush National Historical Park

The Taiya River, located west of Skagway, is one of two major freshwater systems in Klondike Gold Rush National Historical Park. It drains a large mountainous watershed that was, as of 2010, approximately 29% covered by glaciers presently undergoing retreat. Glacial outburst events have caused large floods in the past and help shape this highly dynamic physical setting. The SEAN’s monitoring station is located near the Taiya River Bridge (map) adjacent to the long-established USGS streamflow gage. The Taiya watershed supports chum, pink, and coho salmon populations, as well as Dolly Varden and eulachon. Fish habitat conditions and turbidity fluctuations are particularly important to park natural resource managers.

2019 Observations

• Water temperature in the glacially influenced Taiya River is less responsive to seasonal changes in air temperature than other sites. Nonetheless, 2019 temperatures were often near the upper historic range; average temperature 1 May - 31 October was above the 2010-2018 mean by 0.24°C.
• Dissolved oxygen levels were well within optimal fish habitat range (above 7 mg/L) across all months. Concentrations were stable through summer, then reached above the historic record in the fall.
• pH readings fluctuated more in 2019 than usual but remained within normal ranges and the ADEC standard (above 6.5 and below 8.5). The late season uptick in rainfall did not significantly alter Taiya River pH levels, reflecting greater buffering capacity than at other monitoring sites.
• Specific conductance exhibited more variability this year, reaching both the upper and lower bounds of the historic record. Very low values in the summer reflect snow and ice melt, while storm-driven runoff, transported overground and through soils, increased conductance in the fall.
• Turbidity was lower than typical through much of season–one storm-driven spike occurred in September, but no other extreme values were recorded. Late June and early July turbidity levels were above average, coinciding with a strong meltwater pulse (see discharge plot) that flushed sediment downstream.
• Discharge remained elevated June through August, driven by strong seasonal warming and melt processes as minimal precipitation fell. Sharp storm-generated peaks in September punctuated the otherwise gradual autumn 2019 decline in streamflow; October and November weather systems brought snow rather than rain to the Taiya watershed, which is less evident in these metrics.

Taiya River freshwater data summary, 2019.

Parameter	n	Median	Mean	SD	Min	Max
Temperature (ºC)	3,572	5.48	5.21	1.68	-0.11	9.28
DO concentration (mg/L)	3,572	12.78	12.86	0.46	11.86	14.86
pH	3,568	7.28	7.31	0.16	6.90	7.61
Specific conductance (mS/cm)	3,570	0.03	0.04	0.02	0.02	0.08
Turbidity (NTU)	3,565	44.90	55.01	62.85	1.50	918.80
Discharge (cfs)	3,581	1,728.54	1,979.43	1,455.19	222.82	7,029.48

Daily mean water quality parameters for the Indian River in 2019 (black lines) relative to hourly measurements prior to 2019 (purple points). Bottom panel shows daily mean discharge rates (black lines) from the nearby stream gage and precipitation (purple bars) from the closest weather station.

Shaded regions denote ADEC thresholds for unsuitable fish habitat for temperature (above 13°C), dissolved oxygen (below 7 mg/L), and pH (below 6.5 or above 8.5).

Sitka National Historical Park

The Indian River provides the only significant freshwater and estuarine habitat within Sitka National Historical Park. The 1-km section that flows through the park is a low gradient channel supporting a diversity of anadromous and non-anadromous fish, including four species of salmon, steelhead, Dolly Varden, rainbow trout, three-spine stickleback, and coastrange sculpin. Quality of fish habitat, particularly during low flow and salmon spawning intervals, is a high resource management priority.

Draining a small, steep, and over 50% forested watershed, the Indian River is a mostly surface-water influenced system; discharge closely tracks precipitation events. Moderate development and human activity impact the lowest 2.5 km of the river. The National Park Service and City and Borough of Sitka collaboratively fund the USGS streamflow gage adjacent to the SEAN monitoring site (map), located just upstream of the park boundary.

2019 Observations

• Water temperatures for 2019 were not compared to the long-term mean due to limited data. Fall readings varied from above typical in September to some of the lowest recorded in December. Peak summer conditions that might approach the 13°C ADEC standard are missing from the dataset.
• Dissolved oxygen remained well above the ADEC threshold (7 mg/L) during the sampled months, with late September through December sustaining the highest fall oxygen levels documented to date.
• pH was stable and at the upper edge of the historic record, always within optimal range (above 6.5 and below 8.5). Small fluctuations occurred during precipitation intervals.
• Specific conductance dropped with rain events but otherwise exhibited a low overall magnitude of variability. Fall levels were near the upper edge of the historic range.
• Discharge was consistently low through the spring and summer dry period experienced across Southeast Alaska, followed by several moderate fall storms. For the Indian River gaging station, July 2019 set the record minimum discharge level and August reached near record lows.

Indian River freshwater data summary, 2019.

Parameter	n	Median	Mean	SD	Min	Max
Temperature (ºC)	1,773	6.68	6.71	1.01	4.19	9.66
DO concentration (mg/L)	1,773	13.35	13.38	0.40	12.32	14.38
pH	1,773	7.32	7.29	0.11	6.83	7.48
Specific conductance (mS/cm)	1,773	0.05	0.04	0.01	0.02	0.05
Discharge (cfs)	2,924	87.20	147.03	192.56	10.40	1,400.00

Suggested Citation

Goodwin, D. S., C. L. Amundson, and T. Ziomek. 2021. Southeast Alaska Network water quality monitoring program: 2019 annual update. National Park Service, Juneau, Alaska.

Principle Researchers: Deborah Goodwin, Courtney Amundson, Thomas Ziomek (contact us)

Data in this annual update were collected and analyzed using methods based on established, peer-reviewed protocols and were analyzed and interpreted within the guidelines of the protocols.