Appendix E: Phase 4 Alternatives - HEC-ResSim Alternative Assessment

• Variant (d) shifts the start of the apportionment year in the basic alternatives from the start of the calendar year to November 1st of the previous fall. [...] When the basin is in flood status, the “a_fld_status” state variable equals 1, instead of 0, and the top of the Flood Control zone stays at 1601 ft (488.0 m) until the following two conditions are met: 16 - Flow at Minot, ND < 500 cfs (14 cms) - Lake Darling pool elevation < 1598 ft (487.1 m) Outside of March 20th through May 31st, if both of the above conditions are met, the top of flood control. [...] The primary change in operations required by the addition of the WSA dam safety rules is the addition of an inflow design flood supply level, or IDFSL, at the two Canadian reservoirs. [...] The inclusion of the IDFSL affects operations at the two reservoirs in the following ways: 18 May 1st through May 31st: if the either pool is above its IDFSL, a linear drawdown is initiated to return the pool to its IDFSL by June 1st. [...] Rate of Decrease (Elevation) Like the ROI rules, the elevation rate of decrease (ROD) rules used in the Phase 2 Alternative 9, Phase 3.5 Alternative 608, and Phase 3.5 Alternative 914 models were also adopted for all Phase 4 alternatives and the baseline model at Rafferty, Grant Devine, and Lake Darling reservoirs.