2000 WY EA AOP

• File Number: 8461.450
• Description: EAC/RCC
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 3/6/2000
• Author: Sharon Whitmore ‎(EA Manager)‎
• Title: 2000 WY EA AOP
• Water Supply Pro - Doc Type: Correspondence

2000 Water Year Priorities
Using projected flows at Grand Island and Overton for the 2000 water year (provided to the EAC
by the Districts), shortages relative to the Service's average target flow recommendations were
graphed (Figure 3). Because the Service's higher pulse flow recommendations are more complex
and designed to capture natural variability, they were not used to project these shortages.
Likewise, Service flow targets for a"normal" year were used even though the recommendations
in-full are actually tiered for "wet, normal, and dry" flow conditions. Based on predicted "wet"
conditions for the 2000 water year and projected flows for the central Platte, the Service
identified priorities for each seasonal period (Table 1). Projected shortages by time period are as
follows:
A rox.
Time Period # of Davs Shorta eKAF) Total AF cfs/dav
2-15 to 2-29 15 2.0 30,000 1,000
3-01 to 3-15 15 0.1 1,500 50
5-20 to 5-31 12 0.7 8,400 350
6-01 to 6-20 20 0.8 16,000 400
8-01 to 8-31 31 0.5 15.500 250
71,400
Earlv Spring1(Februarv/March? High flow conditions prevailed throughout late 1999 and early
2000. Flows during this period averaged 2,500-3,500 cfs at Grand Island, roughly in a 2-5
percentile level for the present conditions (OPSTUDY Present Conditions). Comparatively high
flows are expected to continue at least through early spring of 2000 with reservoir fill predicted
by the Districts' for the months of March and April. In addition, central Nebraska has
experienced moderate temperatures with little or no river ice formation, no snow plains cover,
and little precipitation thus far in 2000. Because of these collective factors, early spring is
regarded as a low priority for the Service in the 2000 water year. The Service will continue to
monitor local ice and snowpack formation for the remainder of the winter, as well as
precipitation in early spring (late February and early March) for the effects that river flow
management could have on wet meadow hydrology.
Late Spriniz (Ma, /June) Unless conditions during the January through March assessment period
indicate that EA releases could be effectively used to augment an early spring pulse flow to
promote natural processes of the river and enhance riparian wetland systems, opportunities to
augment May/June pulse flows will be a priority for the 2000 water year. Improved late spring
pulse events are the Service's highest flow priority (Bowman 1994; Bowman and Carlson 1994).
Existing long-term averages for pulse flows are well below Service targets. Current projections,
based largely on reservoir storage, suggest above normal flow conditions in May and June.
Mountain snow accumulation will be monitored at least bimonthly during spring. The timing
and duration of May and June uncontrolled runoff will be closely monitored for opportunities to
augment runoff events with the EA to improve magnitude, 30-day duration, or both.
Summer Julj%-Septemberl To the extent that projections for summer are practical, wet
EA AOP 4 January 31, 2000