Southeast Alaska Network freshwater water quality monitoring program: 2010 annual report.

Sergeant, Christopher; Johnson, William; Moynahan, Brendan

Freshwater water quality is an indicator of ecosystem health and one of twelve priority Vital Signs monitored in the National Park Service’s Southeast Alaska Network (SEAN). In 2010, hourly water temperature, conductivity, dissolved oxygen, and pH data were collected in the Salmon River (Glacier Bay National Park and Preserve) from June 4 through November 9, and in the Indian River (Sitka National Historical Park) from May 26 through September 23. Future annual reports will include data from the Taiya River in Klondike Gold Rush National Historical Park, first installed in 2011. This is the first annual water quality report from the SEAN, representing the beginning of asustained effort to collect long-term, high resolution water quality data in Southeast Alaska National Parks. Annual reports are concise but thorough summaries of the previous season’s data that establish a regular product for park staff, managers, superintendents, and other interested parties. The 2010 report will establish the current water quality status of the Salmon and Indian Rivers and provide a broad comparison of water resource conditions between the two streams. In later years, annual report results will become more park-specific and describe trends within each river. All annual reports and data products are available at the SEAN freshwater water quality website: http://science.nature.nps.gov/im/units/sean/FQ_Main.aspx Both rivers demonstrated similar seasonal temperature trends in 2010. Daily mean water temperature in the Salmon River ranged from 4.0 to 11.0°C, peaking on August 6, while the Indian River ranged from 6.6 to 9.8°C, peaking on August 18. Median seasonal values for conductivity, dissolved oxygen, and pH were significantly different between systems. Compared to the Indian River, the Salmon had higher medians and non-overlapping ranges of values for conductivity and pH. Median DO in the Salmon River was significantly lower than the Indian, but the observed range of values overlapped throughout the season. These results were consistent with expectations for a mostly groundwater-influenced system (Salmon River) versus a mostly surface water-influenced system (Indian River). Short-term snapshots of hourly data viewed over five to ten-day periods demonstrated that directional water quality trends during cool/wet weather periods were generally opposite of trends during warm/dry periods. For example, during a warm/dry period on the Salmon River, conductivity values tended to rise consistently, signifying the increasing contribution of groundwater contributions; during a cool/wet period, conductivity values generally dropped and were cyclical in response to rain events. Both rivers demonstrated similar water quality characteristics in 2010 as those seen in past studies from the same systems or similar watersheds in Southeast Alaska. No 2010 observed water quality parameter values exceeded regulatory thresholds set by the Alaska Department of Environmental Conservation, and no observed values or trends appeared to signal point source pollution or a change to the fundamental water quality of the Salmon or Indian Rivers. Throughout the monitoring period, both rivers exhibited water quality conditions within expected normal ranges.

Southeast Alaska Network freshwater water quality monitoring program: 2010 annual report.

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