FOR 50 years the Army Corps of Engineers carried out orders whose effect was nearly to destroy the extensive natural wonder called the Everglades. Now those orders have been dramatically reversed, and the ever-willing corps has come up with a plan to restore the Everglades, in part by undoing much of its own past handiwork.

The $7.8 billion plan has been vetted on all sides. It has wide support, and while scientists caution that one can never be sure, it is thought to have a reasonable chance of success. The administration, which deserves great credit for having pushed it, will ask Congress later this year to authorize the first phase of the project, whose cost the federal government and state of Florida are to split. The authorizers should say yes. This is not just an effort to restore a lost corner of nature. The long-term water supply and environmental health of the entire southern third of a populous state are implicated.

The Everglades were the ultimate wetland. The southern third of the state was a sheet of water flowing slowly south from Lake Okeechobee. To drain great stretches of this marsh for urban and agricultural use, the Army Corps of Engineers created an enormous public works project of ditches, pumps, levees, etc. The remaining Everglades got too little water; the water came in the wrong amounts and at the wrong time of year; and it was contaminated by agricultural and other runoff. Bird and other once-abundant animal species were depleted; marine life and water quality in Florida Bay were likewise affected; and a region whose problem was once that it was too wet began to confront the possibility of water shortages.

In the name of restoration, the corps proposes pumping less water out to sea, creating new storage capacity in order to regulate flows, punching holes in levees and beneath highways that now impede flows, continuing to buy up land to serve as filtration marshes to remove contaminants, etc. A replumbing project as vast as this, in which man tries to play the role of nature, always has unanticipated and perverse effects. This will be kept flexible with that in mind. Success isn't guaranteed, but the effort is more than plausible, and the government can't not try.