Study Documents Huge Lower Columbia Riverby CBB Staff
Almost two-thirds of the shallow water habitat in the lower Columbia River once available for rearing juvenile salmon and steelhead is gone and the culprits are dikes and dams, according to a new report by researchers at the Oregon Health & Science University.
A computer model developed by Tobias Kukulka, M.S., a graduate student and lead author of the study, and David Jay, Ph.D., associate professor of environmental and biomolecular systems at the OGI School of Science & Engineering, found that 62 percent of shallow water habitat once available to juvenile fish from May to July when the spring freshet pushes the fish towards the ocean is now gone. The study was published in the Journal of Geophysical Research -- Oceans.
In addition, the study was able to separate out those portions of habitat loss attributable to the hydroelectric system for power and flood control, and to that attributed to the claiming of land by diking areas of the lower river. It found that 52 percent of habitat was lost due to dikes used in the lower Columbia River to claim new farmland. In addition, it found that 29 percent of the habitat loss is due to the hydro system, which has a tendency during the spring freshet to level off peak flows that would normally flood lower river lands during May through July. Before the 55 upriver dams were in place, that natural flooding created temporary shallow water areas where juvenile salmon and steelhead could begin their physiological change needed for survival in the ocean.
According to OGI, the "Columbia River hydrology has changed drastically in response to human activities and climate at the same time that salmon populations have greatly decreased." The study looked at a 40-kilometer freshwater stretch of the lower river just above the salty lower river estuary.
"There are few studies on the tidal-fluvial environment," said Jay. "Every river has such an area, and methods used by hydrologists for rivers and oceanographers for estuaries don't work that well. This is also a crucial area for juvenile salmon because many young salmon feed and prepare physiologically and behaviorally in the fresh, shallow waters for a rapid transition to ocean saltwater."
Jay said he was reassured that diking has taken a bigger bite out of habitat than the dam operations.
"There are probably areas where dikes can over time be removed at lower cost than altering flow-management," he said in an interview with The Oregonian. He added that providing more water to simulate peak flows would cost much more than removing some dikes.
The study, which was funded by the U.S. Army Corps of Engineers and NOAA Fisheries, is a part of other work at OGI to understand and predict river flow and habitat in the lower Columbia River. It has also studied the lower river's water level, velocity, salinity and temperature, according to OGI. That work can be seen on the web at www.ccalmr.ogi.edu/CORIE.
Kukulka/Jay study: www.ese.ogi.edu/~jaylab/public/kukulka%26jay_jgr03b.pdf or go to www.ebs.ogi.edu/~jaylab/ and click on "Publications"
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