The Secretary of the Interior - Washington - CO River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead

• Year: 2007
• Title: The Secretary of the Interior - Washington - CO River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead
• CWCB Section: Interstate & Federal
• Description: The Secretary of the Interior - Washington - CO River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead
• Publications - Doc Type: Other

Interim Guidelines for the
Operation of Lake Powell
and Lake Mead
However, given the more complicated proposed operation for Lake Powell under all of
the action alternatives, Reclamation conducted additional investigations and
subsequently refined the operational guidelines to include a combined monthly/annual
methodology to determine the annual release volume for Lake Powell. This
methodology consists of a January 1 determination of the release volume with
appropriate April adjustments to those volumes, and providing the necessary flexibility
to respond to changing inflow forecasts while ensuring that the operation does not result
in excessive changes in monthly releases from Lake Powell.
In addition, comments were also received in both written and oral form from
representatives of the Basin States with respect to the modeling assumptions used for
the Basin States Alternative and the Preferred Alternative, reflected in Appendix S of
the Final EIS. Specifically, the comments were in regard to the coordinated operation
of Lake Powell and Lake Mead when Lake Powell is relatively high and operating near
or in the equalization tier. A concern was identified where the proposed operation
might not respond effectively when Lake Powell is relatively high, Lake Mead is
relatively low, and a reasonably high inflow forecast occurs. Reclamation conducted
additional investigations to identify approaches to ensure some additional water is
released from Lake Powell when this situation arises.
Reclamation refined the proposed operational guidelines to incorporate these changes
(contained in Section 6, 7, and 8 of the Guidelines) and published those refinements on
the project website on November 1G, 2007. An evaluation concluded that these
refinements to the proposed Guidelines would not result in substantial changes with
regard to the environmental effects and fall within the impacts already analyzed in the
Final EIS.
VIII. Environmental Impacts and Implementation of
Environmental Commitments
Hydrologic modeling of the Colorado River system was conducted to determine the
potential hydrologic effects of the alternatives. Modeling provided projections of
potential future Colorado River system conditions (i.e., reservoir elevations, reservoir
releases, river flows) for comparison of those conditions under the No Action
Alternative to conditions under each action alternative. Due to the uncertainty with
regard to future inflows into the system, multiple simulations were performed in order
to quantify the uncertainties of future conditions and as such, the modeling results are
typically expressed in probabilistic terms.
Hydrologic modeling also provided the basis for the analysis of the potential effects of
each alternative on other environmental resources. The Final EIS evaluated 14 resource
areas: hydrologic resources (including reservoir storage and releases, groundwater, and
water deliveries), water quality, air quality, visual resources, biological resources
(including vegetation and wildlife and special status species), cultural resources, Indian
trust assets, electrical power resources, recreation (including shoreline facilities, boating
December 2007 ROD -Colorado River Interim Guidelines for
16 Lower Basin Shortages and Coordinated
Operations for Lake Powell and Lake Mead