Baseline Characteristics of Jordan Creek, Juneau, Alaska

Abstract

Anadromous fish populations historically have found healthy habitat in Jordan Creek, Juneau, Alaska. Concern regarding potential degradation to the habitat by urban development within the Mendenhall Valley led to a cooperative study among the City and Borough of Juneau, Alaska Department of Environmental Conservation, and the U.S. Geological Survey, that assessed current hydrologic, water-quality, and physical-habitat conditions of the stream corridor. Periods of no streamflow were not uncommon at the Jordan Creek below Egan Drive near Auke Bay stream gaging station. Additional flow measurements indicate that periods of no flow are more frequent downstream of the gaging station. Although periods of no flow typically were in March and April, streamflow measurements collected prior to 1999 indicate similar periods in January, suggesting that no flow conditions may occur at any time during the winter months. This dewatering in the lower reaches likely limits fish rearing and spawning habitat as well as limiting the migration of juvenile salmon out to the ocean during some years. Dissolved-oxygen concentrations may not be suitable for fish survival during some winter periods in the Jordan Creek watershed. Dissolved-oxygen concentrations were measured as low as 2.8 mg/L at the gaging station and were measured as low as 0.85 mg/L in a tributary to Jordan Creek. Intermittent measurements of pH and dissolved-oxygen concentrations in the mid-reaches of Jordan Creek were all within acceptable limits for fish survival, however, few measurements of these parameters were made during winter-low-flow conditions. One set of water quality samples was collected at six different sites in the Jordan Creek watershed and analyzed for major ions and dissolved nutrients. Major-ion chemistry showed Jordan Creek is calcium bicarbonate type water with little variation between sampling sites.