Crescent River: a synoptic survey, Lake Clark National Park and Preserve Alaska 1997

Deschu, Nancy

Crescent River, a 518 km2 coastal watershed, lies within the boundary of Lake Clark National Park and Preserve in southwest Alaska. The river flows east and south for 25 kilometers, emptying into Cook Inlet (Figure 1). There are two headwater forks: the Lake Fork which flows from Crescent Lake (10-km long), and the North Fork which is fed from steep headwaters that hold several glaciers. The two single-channel forks meet in a single channel and then at 1.9 km downstream of the confluence, they form a braided mainstem. Crescent River below the confluence of the two forks, although within the park boundary, is on private land held by the Cook Inlet Regional Native Corporation and is subject to development. Sockeye salmon travel up Crescent River and spawn along the shores and in the small tributaries of Crescent Lake. It is not known if sockeye spawn in other areas of the watershed. Due to the importance of sockeye salmon for sport and subsistence fishing in the lake and the potential for commercial logging in the watershed, a site visit was made on September 1, 1997 to take photographs and collect basic information for preparation of a full study proposal at a later time. Chlorophyll which was measured in nearby streams in June, 1997 (Difficult Creek, Hungryman Creek, Bear Creek, Johnson River) is compared to the Crescent River chlorophyll concentrations in this report. Summary: The two upper forks of Crescent River are strikingly different streams in topography, chemistry and some aspects of physical hydrology. The forks mix well by 2 km downstream of their confluence and the river takes on a characteristic lower gradient braided stream form. Based on this short site visit in September, 1997 and the limited amount of data collected, it is difficult to suggest strong trends; however, it is clear that the Lake Fork had lower sediment load, less scour, higher light penetration and higher primary productivity than the North Fork in early September. The chemical and physical aspects of the two forks becomes blended as the mainstem begins to braid. There are extensive research questions that could be addressed on this interesting watershed, particularly as it relates to sediments, nutrients, primary productivity and salmon. Given the high volume of glacial meltwater, questions of how climate change affects melt rate, sediment loading and sockeye production is of great interest. With a majority of the watershed in private ownership, the likelihood of development is higher than other national park areas, and therefore a thoughtful monitoring plan to address the condition of park resources is important.