Little Susitna Water Quality Monitoring
The Little Susitna River is ranked as a high priority waterbody through the ACWA process. The main concerns are with degrading water quality and loss of fish habitat. There are many factors that influence both of these concerns. Through ACWA grant funds, the DEC has been investigating water quality from Hatcher Pass to below the Little Susitna Public Use Facility (PUF). Through these studies, two pollutants are of more serious concern – petroleum hydrocarbons and turbidity.
The lower Little Susitna is at risk of water quality impairment from petroleum hydrocarbon pollution. In 2007 the DEC conducted preliminary petroleum hydrocarbon sampling on the Little Susitna River from the Parks Hwy. bridge downstream to below the Public Use Facility located at river mile 25. Results led to more intensive petroleum hydrocarbon investigations (Total Aromatic Hydrocarbons, TAH, found in gasoline) in 2008, 2009 and planned for 2010 coinciding with the Chinook salmon (May – June) and coho salmon (July - September) fisheries. Data collected has document concentrations of TAH that exceed the water quality standard of 10 µg/L. TAH exceedances were observed primarily in the months of June and August. TAH exceedances ranged from slightly over 10 µg/L to over 75 µg/L (recorded below the PUF in spring 2008.) The volume of water within the Little Susitna River ranged from 251 cfs to 927 cfs during sample dates. The likelihood of exceeding the water quality standard for TAH is closely related to the amount of water in the river. Outboard engines are the source of the hydrocarbons. Affected river miles are RM 15 to RM 27.
Turbidity is the cloudiness or opacity in the river water caused by sediments or other particles. Turbidity measurements provide an indication of the clarity of the water and water quality. This is especially important for fish since increases in turbidity may indicate increases in gill clogging sediments. Increases in turbidity negatively affect fish metabolism, feeding ability, and behavior. In data collected in 2008 - 2009 on the lower Little Susitna, there is an increase in turbidity values near the PUF as compared to measured natural background turbidity upstream near Houston at Miller's Reach. Data indicates a decrease in juvenile coho and Chinook salmon catch rates with increasing turbidity. There was approximately a 60% decline in marcroinvertebrates in the drift between reference sites and sites located below the PUF. Increases in turbidity are likely resulting in changes to the biotic community. Additional data collection is planned for 2010.
1700 E Bogard Rd, Bldg B, Ste 103
Wasilla, AK 99654
Phone: (907) 376-1855
Fax: (907) 376-2382
- 2011 Little Susitna River Water Quality Report
- 2010 Little Susitna River Water Quality Report
- 2010 Little Susitna River Fact Sheet
- 2009 Little Susitna River Water Quality Report
- 2008 Little Susitna River Water Quality Report
- 2007 Little Susitna River Water Ecological Assessment
- 2006 Upper Little Susitna Water Quality Report