Big Muddy River The Big Muddy was not covered by the Wisconsin Glacier, about 70,000 to 10,000 years before present. However, during the melting of that glacier, the level of the Mississippi River was much higher. Water backed up into the Big Muddy Basin, forming a lake much like the artificial Rend Lake but covering a larger area. The ancient lake silted in, forming a flat bottom. After the melting of the Wisconsinan glacier, the level of the Mississippi dropped, allowing the lake to drain. A new channel formed within the old lake bed. This channel meandered in the flat bottom of the
Muddy River (Nevada) the Meadow Valley Wash, forming the principal drainage system for southeastern Nevada. The Moapa Valley area is home to a wide variety of rare and endangered species, including fish, invertebrates, birds, and plants. Three endangered fish inhabit the area: the Moapa dace ("Moapa coriacea"), the Virgin River chub ("Gila seminuda"), and the White River springfish ("Crenichthys baileyi moapae"). These species can be found throughout the various springs, called the Muddy Springs, that feed the Muddy River. The U.S. Fish and Wildlife Service has created the Moapa National Wildlife Refuge at the Warm Springs Natural Area, as part of the Desert