The Trust for the National Mall has announced winning designs for three public spaces around Washington, D.C., but the eventual fate of the one tied to Congress is less certain than the other two.

With the new plans, Constitution Gardens would boast a new restaurant, model boat pond and performance space; the National Sylvan Theatre southeast of the Washington Monument would be refurbished; and Union Square, the 11-acre swath of land beyond the West Front of the Capitol, would swap out the Reflecting Pool.

But late last year, in the thick of the prestigious design competition to revamp areas of the National Mall, Union Square was transferred to Congress as part of the fiscal 2012 omnibus spending bill.

Capitol Hill law enforcement cited security concerns as the primary reason for the transfer of the park containing the Ulysses S. Grant Memorial and the Reflecting Pool.

So while the other two sites can be realized through private funds raised by the trust, Union Square’s renovation hinges on what the Architect of the Capitol and other stakeholders on Capitol Hill think — and whether there are resources available to turn the blueprint into reality. As a Congress-owned space, it cannot benefit from nonpublic money.

If AOC Stephen Ayers and others give the green light, Union Square would look very different. In the vision of the winning architectural team, firms Gustafson Guthrie Nichol and Davis Brody Bond, the park would be reimagined to strengthen its relationship with its surroundings.

The biggest change would be subbing out the Capitol Reflecting Pool, currently the centerpiece of the space, and replacing it with a new “water feature.”

“The current reflecting pool and paths disrupt connections between the Mall and Capitol Grounds, offering little opportunity to enliven the heart of Union Square,” the design proposal reads.

Davis Brody Bond, on its website, describes the pool’s replacement as “a flat and shallow pool [with] discrete sections [that] can be quickly drained to create paved plazas for major events, but on most days the pool offers a transitory and luminous surface that reflects the sky, trees and major monuments of the city.”

The proposed design would add new vegetation to the area, including canopies of trees to provide respite on hot summer days. It also would take into consideration security concerns by creating new areas for surveillance that are simultaneously in harmony with the aesthetic concept.

The winning designs were first reported by the Washington Post on Wednesday, and the trust’s media representatives released a statement announcing the winners this afternoon.

Spokeswomen for both Gustafson Guthrie Nichol and Davis Brody Bond said they would not be commenting until after today’s luncheon marking the fifth anniversary of the Trust for the National Mall, at which point the selections are made official.

Eva Malecki, a spokeswoman for the AOC, did not immediately respond to a request for comment.