National Academy of Sciences (NAS) | January 1st, 2008
Summary
The Klamath River basin, which spans parts of southern Oregon and northern California, has been the focus of a prominent conflict over competing uses for water. Manag
The Klamath River basin, which spans parts of southern Oregon and northern California, has been the focus of a prominent conflict over competing uses for water. Management actions to protect threatened and endangered fish species in the basin have left less water available for irrigation in dry years and heightened tensions among farmers and other stakeholders including commercial fishermen, Native Americans, conservationists, hunters, anglers, and hydropower producers. This National Research Council report assesses two recent studies that evaluate various aspects of flows in the Klamath basin: (1) the Instream Flow Phase II study (IFS), conducted by Utah State University, and (2) the Natural Flow of the Upper Klamath Basin study (NFS), conducted by the U.S. Bureau of Reclamation (USBR). The report concludes that both studies offer important new information but do not provide enough information for detailed management of flows in the Klamath River, and it offers many suggestions for improving the studies. The report recommends that a comprehensive analysis of the many individual studies of the Klamath river basin be conducted so that a big picture perspective of the entire basin and research and management needs can emerge.
Key Messages
If these conclusions were borne out by studies incorporating experimental flows and monitored responses, managers would be able to have greater confidence that decisions to increase flows would have a beneficial effect on anadromous fishes in the lower river
The Instream Flow Study Phase II did not include important water-quality attributes, such as dissolved oxygen levels, nutrient loadings, contaminants, and sediment concentrations, although each has important implications for the vitality of the fish populations of the Klamath River.
The Natural Flow Study and the Instream Flow Study Phase II were major science and engineering investigations, but the linkage of one to the other was only partially achieved.
The Natural Flow Study was seriously compromised by several fundamental issues, including its choice of a basic approach for understanding natural flows, choices of the models for calculations, and serious omissions of factors likely to influence river flows at the Iron Gate Dam gauge site.
The basin and its biota have changed so much in the past century that the implications for the fishes of restoring natural flows are not clear.
The committee concluded that the Natural Flow Study includes calculated flows that are at best first approximations to useful estimates of such flows.
The committee found important shortcomings in the Instream Flow Study Phase II and its use of various models and data. Two major shortcomings use of monthly data and lack of tributary analyses are so severe that that they should be addressed before decision makers can use the outputs of the study to establish precise flow regimes with confidence.
The most important outcome of the Instream Flow Study was that it indicated that increases in existing flows downstream from Iron Gate Dam probably would benefit fish populations through improved physical habitat associated with more water and through reduced water temperatures.
There was a lack of a thorough assessment of the relationship between flow-data time series and the behavior of different species and life stages and the population dynamics of coho and Chinook salmon
When the science needs for the basin are better characterized, the individual studies necessary to create a sound science-based body of knowledge for decision makers and managers will be more easily identified.
current flow regime. These are improvements in flow because they include intra- and inter-annual variations and probably will enhance Chinook salmon growth and young-of-the-year production.
is not possible to know how well the recommendations apply to any one species or to all the species as a whole. Indeed, most of the information was from Chinook salmon, which suggests that confidence in its applicability to that species would be greater than to other species.
of the representativeness of the reaches used for detailed study, and the statistical approach to analyze the calculated set of instream flows did not use normalized data and did not have provisions for identifying serial autocorrelations.