Despite its name, Delta Marsh is no longer a river delta. However, it was originally the delta of the Assiniboine River, which flowed into Lake Manitoba from the southwest until approximately 2500 years ago. (The current course of the river continues east past Lake Manitoba until it intersects the Red River in Winnipeg).
Delta Marsh is a wildlife breeding and migration staging area of major importance. Waterfowl and songbirds are especially abundant in the marsh, either as breeding residents or seasonal migrants. The wooded dune ridge is also migratory pathway for passerine birds.
Hunting is permitted in a portion of the marsh in the autumn by sportsmen, and by First Nations year round, under the auspices of the Delta Marsh Wildlife Management Area, which controls hunting pressure and safeguards the marsh environment. Canada geese, mallard ducks, and snow geese are the three primary bird species hunted, both in the marsh itself and in nearby grain fields, where these birds feed on autumn days. Of these, Canada geese and mallards breed in the marsh, while snow geese are strictly seasonal migrants. Hunting of waterfowl contributes in a significant way to the local economy. Other game, including white-tailed deer, are also hunted in and around the marsh, and beaver and other fur bearing mammals are commercially trapped.
Much of the marsh is still quite pristine. The barrier dune ridge has however been settled with cottages, and Delta Beach, on the lake-side of the ridge, is a popular swimming beach in summer. The access road to the beach does however cross the marsh along a relatively dry path, and so disruption to the marsh habitat is minimal.
A more obvious man-made disruption of the marsh is the Assiniboine River Floodway, which crosses the marsh near its west end. This floodway diverts Assiniboine River floodwater northwards from just upstream of the town of Portage la Prairie directly into Lake Manitoba, thus protecting the town and the city of Winnipeg from spring flooding. Controversy continues to surround the issue of the environmental impact of the floodway upon the marsh.
The Delta Waterfowl Research Station was established in 1938 east of Delta Beach to carry out waterfowl research.
In 1966, the University of Manitoba leased lands at the west end of the marsh from the Province of Manitoba and developed the Delta Marsh Field Station (University of Manitoba) as a teaching and research centre.
The Delta Waterfowl Foundation is an international research and conservation organisation inspired by and named for Delta Marsh.