The state of Florida has established a program called Acceler8 with the mission of - you guessed it - accelerating Florida's ecological restoration efforts. There are eight projects underway, and one will become the largest manmade reservoir in the world, measuring 25 square miles, with a capacity of 62 billion gallons of water.
The gargantuan reservoir, which has a projected completion date of 2010, differs from other reservoirs in that it does not connect to a natural water source, but rather will be dug in a freestanding plot of flat land, and surrounded by a 26' levee. Water management personnel will be able to use the reservoir to control water and nutrient levels in the Everglades' Lake Okeechobee, as farming and development have led to harmful imbalances which have killed plants and wildlife in and around the lake. The reservoir will also help mitigate floodwaters -- an important function in an age of climate change. This is mega-engineering, but towards a goal of environmental restoration.
A post at the landscape architecture blog Pruned has some interesting related links for those who love wetlands and hydromechanical engineering. A bit more detail on this project can also be found at Wired News.