Longputt, there is a fundamental difference between federal dams and federally licensed dams by FERC (Federal Energy Regulatory Commission). Federal dams have no inherent legal mitigation obligation, zero, none, nada, except whatever Congress decides to impose under the various editions of the federal Water Development Act. Congress authorized the Mitchell Act in response to salmon losses from Columbia River dams, but any objective analysis would describe the mitigation as partial, at best. Then came the Lower Snake Compensation Act well after completion of the 4 lower Snake federal dams. Whether the benefits of that have measured up to "complete" is very likely debatable. But with federal projects, you get what Congress decides, unlike in a civil case of loss due to cause and effect.
In the case of federally licensed dams, the Federal Power Act (FPA) applies. Enacted in 1927, they never saw a dam they didn't like, and would issue terms and conditions to make most any, even a loser of a project, profitable for its owner. Over time, rational sense gradually infused amendments to the FPA, partly by the prodding of several key lawsuits. So FERC in its Mead Decision in (year?) came to its senses and concluded that "mitigation proportional to impacts" of a project is a logical and rational way to go about dam licensing, and it isn't the federal government's responsibility to make every dam a profitable one. That is the job of the license applicant, to propose projects that are engineeringly, economically, and environmentally feasible.
So when the five mid-C PUD dams came up for re-licensing in the 1990s and early 2000s, the standards for nearly everything had changed from when they were originally licensed, including fisheries mitigation. And that is why we have seen such dramatic and significant improvements in upstream and especially downstream fish passage come about. While perfect accounting is impossible, the intent of the mid-C licenses and mid-C Habitat Conservation Plan is that there will be as many salmon and steelhead with the dams in place as there would be if the dams were not there at all.
Perfect accounting is impossible for many reasons, but among them are: the federal dams are not held to the same standard, and they kill mid-C fish, variations in ocean survival, the Blob, PDO, irrigation diversions and return flows, land use and development, and the usual host of suspects.
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