SiouxLand

From Page 7:

Under all runoff scenarios modeled for the AOP, the March 1 and May 1 System storage is above the Gavins Point spring pulse precludes of 40.0 MAF. The peak magnitude of the March pulse is 5,000 cfs over navigation flows. Based on the technical criteria, the peak magnitude of the May pulse would be 20,000 cfs under the Upper Decile and Upper Quartile runoff scenarios, 16,000 for Median runoff and 12,000 cfs for Lower Quartile and Lower Decile runoff. The actual peak magnitude of the May pulse will be determined based on the actual System storage and the May 1 runoff forecast. The Master Manual technical criteria include safeguards to minimize the risk of flooding associated with the spring pulses. Both spring pulses may be reduced or eliminated due to the downstream flow limits, shown on Plate 3, which are well below the channel capacity of the Missouri River. These flow limits are identical to the most restrictive flood control constraints presented in the previous Master Manual and provide a similar level of flood protection. An additional safeguard is the incorporation of observed and anticipated precipitation into the daily river forecast to provide greater assurance that flows will remain below the downstream flow limits during the duration of the spring pulses. For simulation purposes, the magnitude of the May pulse for Median and above runoff was limited to 10,000 cfs due to the downstream flow limits. Water for the spring pulses will be withdrawn from one or more of the upper three reservoirs and/or Fort Randall depending on releases required to maintain steady to rising pools during the forage fish spawn and other considerations including impacts to historical and cultural sites and the need to evacuate stored flood waters. Prior to implementing the May pulse, the Corps will coordinate with the affected stakeholders. The Corps will also work closely with the USFWS to insure the planned implementation of the spring pulses meet the intent of the 2003 Amended BiOp.

From Pages 14-15:

Gavins Point releases may be quite variable during the 2011 navigation season but are expected to range from 22,000 to 52,000 cfs. Release reductions necessary to minimize downstream flooding are not reflected in the monthly averages shown in the 15 simulations but will be implemented as conditions warrant.

From Page 16:

Oahe Dam. Releases in the spring and summer will back up those from Gavins Point Dam. The pool level should be steady to rising in the spring during the fish spawn under median and above runoff scenarios. Depending on the timing and distribution of runoff, a level or rising pool at Oahe is not likely under the two lower runoff scenarios.

Page 21:

A. Flood Control. All runoff scenarios studied will begin the March 1, 2011 runoff season at the desired 56.8 MAF base of the annual flood control and multiple use zone. Therefore, the entire System flood control zone will be available to store surplus runoff. The System will be available to significantly reduce peak discharges and store a significant volume of water for all floods that may originate above the System. Being at the base of the annual flood control and multiple use zone will also provide full support for all of the other multiple purposes of the System.