Hydrologic studies on a major salmon spawning habitat
Hydrologic studies on a major salmon spawning habitatAfter a scoping visit for National Audubon, Dan’s next contract in Greater Chilkat Watershed was more focused and technical, for Alaska Dept of Natural Resources, “designed to identify mechanics of groundwater flows believed to move through Tsirku fan, from apex to margins with Chilkat River.”
This one involved groundwater wells and temperature measurements. Although the report was highly quantitative, Dan’s synopsis of post-glacial history is worth quoting here
“Where Tsirku fan met the larger Chilkat River—probably more in the middle of the valley than presently—springflows from coarser Tsirku sediments emerged along flood channels of Chilkat River. These post-glacial springflows were of good water quality, contained adequate dissolved oxygen and provided a sustained flow even during cold periods of winter. A race of Chilkat River chum salmon with distinct preference for the Tsirku River springflows began its development. The centuries following the beginnings of salmon in the Tsirku saw marked glacial recession, valley up-building, and pioneering of vegetation in the flood plain . As the Tsirku fan enlarged and enveloped islands of vegetation, it forced the confluence margin and the Chilkat River to the east side of the valley, increasing the reservoir capacity of the fan so that larger sustained springflows were possible.”
Establishment of a large chum salmon run to the mouth of Tsirku River was followed by annual fall migrations of Bald Eagle, and much later by migrations of commercial fishermen . These dependencies are the fundamental reasons for our studies.”
