Chatfield's water may toil harder

Plan adds storage to its flood-control, recreation purposes

Jerd Smith, Rocky Mountain News

Tuesday, April 26, 2005

When Linda and Roger Perry built the first 14 boat slips at the Chatfield Reservoir marina in 1982, only a few people knew the lake existed.

In the 23 years since, the Perrys have built more than 300 boat slips, and Chatfield now reigns as the largest liquid playground in the metro area, luring more than 1.5 million visitors annually.

But now the crown jewel of the Colorado State Parks system may be asked to take on a more labor-intensive role - to provide water storage for 16 metro-area and Front Range communities.

If the $100 million-plus deal is approved, it's likely to be the first in a long line of proposals to reinvent federally owned dams and reservoirs, making them work overtime to serve an increasingly water-short American West.

On a sunny April afternoon, weeks before the summer season opens, motorboats are already carving frothy paths across the reservoir as fishermen search for walleye along its shores.

"Even though it's not that much water, it's all we've got," Linda Perry said. "Our boaters make the most of it."

Completed in 1977 by the Army Corps of Engineers, Chatfield was originally built to control flooding by capturing the roaring waters of the South Platte River and Plum Creek during periods of high flows.

Its other mission was to help keep metro Denver residents cool and happy during Colorado's sometimes blistering summers.

Now, to make room for water needed by such fast-growing communities as Castle Rock, Parker, Highlands Ranch and Brighton, the Corps of Engineers is being asked to slightly reduce the amount of space it reserves to capture flood waters, allowing that same space to be used for municipal water storage.

If the corps agrees, it means 20,600 acre-feet of storage space - enough for more than 41,000 urban families - will be created almost overnight. A final decision is expected in 22 months.

The Colorado Water Conservation Board, which is spearheading the project, believes that the reservoir's giant storage pool can be safely rearranged.

Back in the 1960s, according to Larry Lang, manager of flood protection at the Colorado Water Conservation Board, the corps used national precipitation standards to design portions of the project. That standard relied too heavily on Midwestern and Eastern rainstorms in determining the size of the project, Lang said.

Newer studies show that Western storms are much shorter than those used in the national standard, and therefore generate less water, Lang said.

"We sometimes do overdesign projects," said Martin Timmerwilke, who is overseeing the Chatfield proposal for the Corps of Engineers. "Right now we're taking a look at whether we really need all that space."

The change in use would raise Chatfield's shoreline as much as 12 feet, forcing relocation of the swim beach, marina, several boat ramps and some picnic areas.

It will also cause more frequent fluctuations in lake levels as more water is stored and then released to cities and farmers.

To accommodate those changes, more than $30 million will likely have to be spent on such projects as relocating boat ramps and wetlands and recontouring the shoreline, Lang said.

People such as the Perrys say that's OK as long as the popular recreation haven is improved as a result.

But Colorado State Parks Director Lyle Laverty wants more data before he's willing to sign off on the deal.

"We still have a whole lot of questions," Laverty said. "What they're doing now - getting good information - is critically important because we really don't know, for instance, what kind of fluctuations we're going to have or when."

New uses for old projects

Throughout the 1900s, Western states relied primarily on two federal agencies, the Corps of Engineers and the Bureau of Reclamation, to develop and build massive reservoirs for a region devoted to large-scale farming, not rooftops.

Now states are looking to those same agencies to create options for coping with chronic drought and a population boom that shows no sign of easing.

"Projects like the one at Chatfield are going to start happening more and more," said Ed Warner, manager of water resources at the Bureau of Reclamation in Grand Junction.

"Eventually, we're going to have to look at every (water) project we have and ask if it's still needed for its original purpose. If the answer is no, we'll see what new uses can be contemplated."

Among water utilities, reallocating Chatfield's storage space makes sense because it doesn't require finding a new reservoir site or building a massive dam.

Those thorny issues are part of what defeated the Two Forks Dam proposal in the late 1980s. Two Forks, proposed for the southwest foothills above Chatfield, would have provided nearly 1 million acre-feet of water storage for Denver and its suburbs.

But a belief that less expensive, less environmentally damaging water storage options could be found ultimately caused federal regulators to pull the plug.

During the wet 1990s, water storage was the least of most communities' concerns as Colorado entered an era of unprecedented growth.

But the recent drought and looming growth-related water shortages have changed all that, forcing dozens of Colorado communities to begin an urgent search for new water supply and storage options.

So motivated are they to see Chatfield's space rearranged that, in negotiations last year, they agreed to cut nearly in half the amount of space each would claim.

"That was a real breakthrough," said Marc Waage, a water resource manager at Denver Water who helped lead the water talks. "Everybody had to give up quite a bit of what they wanted."

Denver, which already stores some water in Chatfield, won't seek space in the new pool because it doesn't fit well with its long-term water supply plans, officials have said.

But Denver is asking those who do get new storage space to time their water releases from Chatfield to improve stream flows in the South Platte River as it meanders through Denver.

"We've been trying for years to get that done," Waage said.

Monitoring Chatfield project

Environmental groups are also watching the Chatfield project closely to ensure that wetlands and fishing grounds are adequately protected and that fast-growing communities use their new supplies wisely.

"We want all of (the suburbs) to come up with a workable conservation plan," said Mike Mueller, a Sierra Club member tracking water issues in the South Platte River Basin.

"Lack of conservation is one of the things that killed Two Forks. We don't plan to stop this one, because we would rather see them doing this than building a new dam. But we want it done in an environmentally responsible manner."

Several key steps remain before the Chatfield redesign is either approved or rejected. In July, the Corps of Engineers expects to finish its own feasibility study on rearranging the flood pool.

In August, studies showing reservoir fluctuations will be finished. Next year, an extensive environmental impact statement will be completed, with a final answer due from the corps in early 2007.

If the answer is yes, Lang, of the Colorado Water Conservation Board, believes work on the shoreline, boat ramps and marina could be completed by 2008.

"We're trying to make this a priority Colorado project (to the federal government)," Lang said. "So far, there aren't any deal-breakers. One way or another, we think we're going to get this thing done."

smithj@RockyMountainNews.com or 303-892-5474