Southeast Alaska Network freshwater water quality monitoring program: 2013 annual report

Sergeant, Christopher; Johnson, William

Freshwater water quality is an indicator of aquatic and terrestrial ecosystem health and one of twelve priority Vital Signs in the National Park Service’s Southeast Alaska Network (SEAN). In 2013, hourly water temperature, specific conductance, dissolved oxygen, and pH data were collected in the Salmon River (Glacier Bay National Park and Preserve) from April 29 through November 18, and in the Indian River (Sitka National Historical Park) from April 30 through November 7. The same parameters plus turbidity were collected in the Taiya River (Klondike Gold Rush National Historical Park) from April 16 through October 2. Annual reports are concise data summaries that establish a regular and timely product for park staff, managers, superintendents, and other interested parties. This fourth annual water quality report from the SEAN represents the continuation of a long-term, high resolution water quality dataset in Southeast Alaska National Parks. All annual reports and data products are publically available at the SEAN freshwater water quality website: http://science.nature.nps.gov/im/units/sean/FQ_Main.aspx Compared to previous monitoring seasons, 2013 was an exceptional year for minimum and maximum water temperatures in the Salmon and Indian Rivers. Daily mean temperature in the Salmon River ranged from 1.6 to 11.8°C and peaked on September 7, while the Indian River ranged from 3.3 to 10.7°C and peaked on August 31. Both rivers demonstrated higher than recent average summer temperatures. From mid-April through early June, water temperature trends in the Taiya River were much colder than 2011-2012. After early June, water temperatures appeared similar to the past two summers, likely reflecting the influence of glacial melt water buffering the variability of the summer thermal regime. Daily mean temperature ranged from 1.2 to 6.7°C, peaking on July 27. In the Taiya River, turbidity ranged from 0 to 390 NTU and appeared synchronized with high flow events. Patterns in the medians and distributions of specific conductance, dissolved oxygen, and pH in the Salmon and Taiya Rivers were generally similar to previous years. While 2013 pH and specific conductance measurements from the Indian River remained similar to previous years, dissolved oxygen levels were the lowest ever observed since the start of SEAN water quality monitoring, reaching a minimum of 1.7 mg/L on August 29. During August 2013, a combination of warmer than average air and water temperatures, low stream discharge, and extremely high abundance of spawning salmon created poor Indian River water quality conditions. No observed values or trends such as abnormally high specific conductance signaled point source pollution or a change to the fundamental water quality of the Salmon or Taiya Rivers. The Indian River should be monitored closely in future years to determine the frequency of low dissolved oxygen events during the summer.

Southeast Alaska Network freshwater water quality monitoring program: 2013 annual report

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