New dams found to be feasible solution for future water shortages in South Platte River Basin

New dams found to be feasible solution for future water shortages in South Platte River Basin

Date Posted: 3/11/20

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Soon after the Colorado Water Plan was approved in 2015, water users came together in unprecedented numbers to discuss approaches to meet each river basins’ forecasted water shortage.

On Tuesday, the South Platte River Opportunities Working Group, better known as SPROWG, presented its latest study on a possible solution — an intricate set of dams and pipelines that could increase the region’s yield by at least 50,000 acre-feet of water for municipal and industrial purposes, and 10,000 acre-feet for agriculture.

While municipalities like Boulder and Longmont have secured enough water to meet their expected build-out — especially if the Windy Gap Firming Project is approved — for towns like Frederick and Firestone, which continue to expand outward, this additional water will be critical to their survival.

“Colorado-Big Thompson water (which uses water from the Colorado River pumped under the continental divide to support communities along the Front Range) is nearly gone and you can see that in the price,” said Ken Huson, Longmont’s water resource specialist who also serves as the Boulder County’s representative on the South Platte River Basin Roundtable. “It’s about $80,000 an acre-foot, so if that’s your plan, you better come up with a new one.”

The solution SPROWG came up with is a system of reservoirs and pipelines that could capture an estimated 300,000 acre-feet of South Platte River water that leaves Colorado each year above the amount needed to satisfy an interstate compact with Nebraska.

To accomplish this, the study presented on Tuesday laid out four possible scenarios.

The first proposed creating three reservoirs; one with 25,000 acre-feet of storage near Balzac, one with 150,000-acre-feet near Kersey, and one with 45,000 acre-feet near Henderson. Pipelines would also be installed and to move water upstream and reuse it for meeting municipal demands.

The study estimated this configuration fully met future municipal demands in 64 of 69 years, and in those years at least 90% of the municipal demand was met, However, agricultural needs were only met 9% of the time in some areas because much of the water is forced to remain in the river for use in the Denver metro area.

The second option solved this issue by shifting 50,000 acre-feet of storage capacity from the reservoir near Kersey to the Balzac reservoir and installing a large pipeline directly connecting the Balzac reservoir to the metro Denver area. In doing so it increased the capability for water exchanges, resulting in agricultural needs being met in two of the basins’ three districts while reducing the overall diversion from the river by 5,000 acre-feet.

Using the same pipeline, the third option allowed for an additional 2,000 acre-feet of water to be delivered for agricultural use by adding a fourth reservoir with 8,000 acre-feet of storage near Julesburg. In doing so, it slightly increased the overall diversion as compared to the previous options, totaling to 223,000 acre-feet.

The study’s final scenario, which also incorporated the pipeline between Balzac and Denver, determined higher projected water demands could be met while still providing an additional 3,000 acre-feet of water to agriculture if the overall storage capacity of all four reservoirs were doubled, allowing for over 400,000-acre-feet to be taken from the South Platte River.

While the South Platte River Opportunity Working Group said environmental and recreational concerns could be addressed in all four scenarios by releasing water from reservoirs and designing the reservoirs to create new wetland habitat, groups like Save The Colorado and WildEarth Guardians have successfully opposed any project that proposes a new diversion, let alone 400,000 acre-feet of diversions.

“A multi-billion-dollar scheme to further drain and destroy the already degraded South Platte River will certainly inspire spirited opposition throughout the permitting process — I can almost guarantee it,” said Gary Wockner, director Save The Poudre and Save The Colorado

The other hurdle, of course, if funding.

If the water accumulated in this system is left untreated, the estimated costs, including 50 years of operation and maintenance costs would be $1.8 to $2.6 billion, which equates to $25,800 to $33,400 per acre-foot.

If the water is treated, the project would cost between $3.2 and $4.4 billion, or $44,100 to $58,300 per acre-foot.

Despite the costs, the study’s authors found the project is both financially and technically feasible. And convinced conservation methods cannot make up for future shortages, the members of SPROWG said it’s an important project to pursue.

“While communities in the South Platte River basin continue to make great progress in decreasing water demands through conservation and reuse, and are actively pursuing projects and strategies to meet our future demands, there remains a need for additional supplies,” Lisa Darling, executive director of the South Metro Water Supply Authority and advisory committee member, wrote in a statement announcing the release of the study.



Written by John Spina, a resources reporter for the Longmont area covering everything from the environment to business