Reservoirs Filling, Still Below Normal

Reservoirs Filling, Still Below Normal

March 27, 2009

Reservoirs in the Platte and Republican river basins have been recovering over the past year and two are near or at capacity.

Platte River Reservoirs

For the first time since the late 1990s, runoff from snow melt in the upper Platte River basin was above normal. Even with improved runoff and current projections for near normal runoff in the upper Platte basin, it will take at least one more winter of normal to above normal snowfall to bring these basins back to full pool.

Wyoming Platte River reservoirs had dramatic lake level rebounds during the last year. As of March 20, Seminoe Reservoir has 515,000 ac/ft of storage compared to just under 200,000 ac/ft at this time last year. Pathfinder Reservoir has 406,000 ac/feet compared to 180,000 ac/ft at this time last year. Glendo Reservoir has 317,000 ac/ft of storage which is nearly identical to last year's total.

Table 1. Current reservoir storage as percent of capacity.
Republication River System
Harlan County
100%
Harry Strunk
95%
Hugh Butler
76%
Swanson
51%
Enders
36%
Platte River System
Total
49%
In Nebraska, Lake McConaughy began releasing water this week to meet mandatory requirements and to provide an environmental account pulse flow. They expect to release 75,000 ac/ft in April and receive approximately 50,000 ac/ft of inflows for a potential decrease of 25,000 ac/ft in the reservoir. In March McConaughy had 846,000 ac/ft of storage compared to 702,000 ac/ft last year. By late April, officials expect it to have 875,000 ac/ft. Inflows the last four weeks have averaged 700-800 cubic feet per second (cfs) — approximately 70% of normal.

The total storage in the Platte River reservoir system stands at 2.1 million ac/ft compared to 4.3 million ac/ft when full. The entire system stands at 48.6% of capacity compared to 37% of capacity at this time last year. This represents a 600,000 ac/ft improvement from this time last year. With normal moisture in the Platte basin through late April, total reservoir storage could approach 2.8 million ac/ft.

Republication River Reservoirs

Republican River basin reservoirs also have seen improvement during the past year, with Harlan County Reservoir at full pool. Harry Strunk Reservoir stands at 95% of capacity, Hugh Butler Reservoir at 76% of capacity, Swanson Reservoir at 51% of capacity, and Enders Reservoir at 36% of capacity. Harry Strunk and Hugh Butler likely will fill to capacity, with an outside chance for Swanson Reservoir to reach capacity if ample moisture falls during the next six weeks. Enders Reservoir has little chance of recovery and will require several years of favorable moisture patterns before significant recovery can be expected. 

Al Dutcher
Extension State Climatologist