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239 The frequency and magnitude of river flow peaks are determined by many variables . In general, they vary directly with precipitation intensity, speed of snowmelt , and slope steepness. They tend to vary inversely with soil infiltration rates, vegetation density, and diversions to reservoir storage. In the Platte Basin, flow peaks produced by snowmelt have tended to arrive in May and early June. They also appear in response to intense summer storms that can, with devastating suddenness, send walls of water crashing down river channels—uprooting vegetation , carrying heavy sediment loads, configuring sandbars, and generally rearranging riparian habitats for people and other living things. They lose energy and concentrated mass with increasing distance as they disappear into bank storage , river bottoms, revived wetlands, and diversion and storage structures. Peak flows are prized as essential to river restoration and diversity in biotic webs. They are also treasured by water providers who have not yet put together the capital, technology, and organization to capture these remnants of the pre-settlement river and to divert them for thirsty customers. How could peak flows be divided among the conflicting agendas? An Unwelcome conversAtion TheNorthPlatteRiverhadbeencollaredbyaseriesof on-channeldams.Theshape of its flows would be largely determined by manipulating gates from Seminoe and Pathfinder all the way to McConaughy. However, the South Platte stream had not been dammed below Denver, which meant its tributaries with mouths north and C h a p t e r 2 0 regime of the river—sharing Peak Flows Colorado and the USFWS Struggle on the South platte r eg im e oF t h e r iv er —Sh a r in g pea k Fl oW S 240 east of Denver—Clear Creek, St. Vrain, Big Thompson, Poudre, Bijou Creek, and Lodgepole Creek, to name a few—could capture and deliver flashy flow spikes to the main South Platte channel. U.S. Fish and Wildlife Service (USFWS) analysts would hang a critical part of their biological opinion on the importance of preserving some fraction of Colorado South Platte peak flows. In Colorado’s view, the entire point of its plan to replace post-1997 depletions was to send sufficient water downstream to fill in the holes in the river imposed by South Platte water users. Now the USFWS was saying the depletions plan that had been formulated and placed into the 1997 Cooperative Agreement (CA) would not sufficiently protect post-1997 depletions. To South Platte water users, the concept was shocking. What had begun as a straightforward plan—cover historical depletions with Tamarack I and III, offset new depletions with Tamarack II, participate in program acquisition of habitat lands, support monitoring and research—had descended into a tangled mess. For water providers, the idea—the division of peak flows under a federal environmental agenda—represented an unwelcome “skunk” at the table. The success of the overall negotiations was importantly held hostage to the outcome of the peak flow discussions. If Colorado and the USFWS could not make peace on the issue, the entire three-state negotiation could disintegrate, and all the water users would find themselves standing among the tormented in line at the door of Endangered Species Act (ESA) Section 7 consultations. The issue was so important and potentially polarizing that for years it had been briefly and repeatedly broached and quickly abandoned. It had surfaced in discussions in 1994, just prior to the agreement that year among the governors of the three basin states to engage in a systematic effort to negotiate a program that would eventuate in the 1997 CA. But the very thought that the USFWS would stake a claim to an unknown fraction of peak flows so greatly alarmed the states, especially Colorado, that the subject was put aside in time for the governors and the Department of the Interior (DOI) to sign the CA. At no time did the states’ negotiators accept the logic advanced in the USFWS in-stream flow document (Bowman 1994), which incorporated language advocating the preservation of peak flows. Water provider rejection of the federally proposed package held fast without exception, even when the final program document was released in December 2005 and revised in 2006 prior to being signed by the governors of the three states and DOI authorities. Prior to launching the cooperative habitat recovery program on January 1, 2007, the states placed disclaimers at several points in the text of the final program document (Platte River Recovery Program 2006), disassociating themselves from any endorsement of USFWS in-stream...

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