WY 2005 EA Release Update and Pulse Flow

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EA Pulse Flow Implementation FWS Decisiom-Making Considerations February 3, 2005 Reasons for not pursuing an ApriUMay EA, Pulse Release in 2005: • Island leveling on Rowe and Crane Trust properties has not yet occurred • Additional clearing/leveling by Private Lands in 2005 will not occur until mid July/early August • Except for Cottonwood Ranch, very little habitat monitoring is in place • Currently the only possible implementatian alternative is an April/May pulse. Because of expected low base flows, the estimated amount of EA water needed is 62 kaf for 1:his alternative (without power inference) • With the April/May pulse, as mode:led, little to no South Platte flows to build on, a minimal pulse is expected (i.e., about 3 days @ =3,000 cfs at Overton) • April/May pulse, as modeled, may mot be conducive for "first-wave" vegetation removal (greatest potential for vegetation scour is in disked areas after germination) • Additional work needed on preliminary EA pulse release plan (e.g., explore options tc? improve the EA pulse release through poNver interference) • More EA water will be retained in ]Lake McConaughy for use in implementing a Feb/Mar pulse release in 2006. Reasons for a commitment to imiplementing a Februarv/March EA Pulse Rele:ase in 2006: • Existing habitat conditions justify use of EA water to facilitate a pulse flow • River conditions are not expected to improve in 2005 or 2006; conditions should remain good for "testing system plumbing" in :?006 • Additional Private Lands river- channel disking will occur in late summer/late fa11:Z005 • With reasonable certainty of a pulse flow in 2006, island leveling activities will be undertaken on both Rowe and Crane Trust pr-operties • Land management activities at Cottonwood Ranch and associated USGS monitoring can be utilized in conjunction with 2006 EA pulse releases • The pulse flow work group's preliminary EA pulse release plan will be completed. and may require less water than the 62 kaf alternative • 2006 storage at Lake McConaughy will provide both EA volume for the pulse operation and carryover for future needs • Post-ice out conditions in Febiruary/March expected to provide better base flows for the pulse release than April/May • Post-ice out conditions in Febiruary/March have better potential for vegetation scour than in April/May • With reasonable certainty of a pulse flow in 2006, involvement/commitment of F'latte River partners to increase 2