FEASIBILITY OF EXTENDING AN ARTIFICIAL SALMON SPAWNING STREAM NEAR HYDER, ALASKA

Marx Creek, near Hyder in southeast Alaska, is a groundwater-fed, artificial salmon spawning stream constructed in the late 1980s in order to enhance the habitat of the atypically large chum salmon. Due to the success of Marx Creek, an extension was built in the early 1990s, lengthening the creek to approximately 5,900 feet. However, the extension has not shared the same success as the original channel. Its success has been limited primarily by the infiltration of silty water from the Salmon River through its flood-control dike. The infiltrated water then flows into the headwaters of Marx Creek, resulting in a turbid stream environment that is not conducive to the spawning of chum salmon.

The objective of this project is to determine whether baseflow from the groundwater system is sufficient to support a proposed 1,000-foot extension of Marx Creek. The extension would be constructed approximately 500-feet east of the existing channel, and would connect with the existing Marx Creek at a point downstream of the sediment-settling weir. The location of the new channel would prevent the turbid water infiltrating through the dike from reaching the new channel, as it would flow into and settle out in the existing Marx Creek.

In order to accomplish our objective, 20 monitoring wells were installed on site. Pumping and slug tests were performed to determine the aquifer's hydraulic conductivity at each of the well locations. Hydraulic conductivity values of 0.5 to 420 feet per day were measured. A Solinst Levelogger was then installed in each of the wells to record daily water-level fluctuations. Data were downloaded from the Leveloggers after a period of 117 days (July-November), and a maximum water-level fluctuation of four feet was recorded. Discharge measurements were also made at each of the 16 weirs along the upper portion of Marx Creek. Each weir represents a one-foot elevation change in the creek, with Weir 1 having the highest elevation. At the headwaters of the creek in Weir 1, a discharge value of 31,086 cubic feet per day was recorded. The discharge measurements increased downstream, with Weir 16 recording the highest measurement of 972,000 cubic feet per day. These data will be used to create a Visual MODFLOW model.