Озеро Бют-де-Морт в Висконсине

Lake in Wisconsin

Big Lake Butte des Morts (,/b//juː//d//ə/'/m//ɔər/) is a shallow freshwater lake located in the U. S. state of Wisconsin, in Winnebago County. It is part of the Winnebago Pool (also known as the Winnebago System) of lakes in east central Wisconsin, along with Lake Winnebago, Lake Poygan, and Lake Winneconne. The lake is fed by the Fox River in the southwest and the Wolf River draining from Lake Winneconne in the northwest, and drains via the Fox River southeast into Lake Winnebago.

With a surface area of , it is the second smallest of the Winnebago Pool Lakes after Lake Winneconne. Much of the lake is flooded marshland, which was created by the damming of the Fox River downstream in Menasha in the 19th century. It is rather narrow, with a maximum length of but a maximum width of just Its total watershed (the combined drainage areas of the Fox and Wolf Rivers plus minor tributaries) is Much of these pollutants enter the watershed from agricultural and urban runoff. The water is typically a murky brown or green color, with high turbidity, though prior to the 1970s the water was reported to be much clearer. Lake Butte des Morts has been the subject of numerous DNR management and monitoring projects aimed at protecting or improving water quality, often alongside other bodies of water in the same watershed. Wetland plants common in and around the lake are American lotus, common reed, and wild rice. Invasive species include Chinese mystery snail, curly leaf pondweed, Eurasian watermilfoil, round goby, rusty crayfish, and zebra mussel.

The city of Oshkosh lies between Lake Butte des Morts and Lake Winnebago. The unincorporated community of Butte des Morts lies on the lake's northern shore, west of Oshkosh. Lake Butte des Morts is part of the Fox Wisconsin Waterway, which used to be used to travel between the Mississippi River and Lake Michigan, but with the closure of both the Portage Canal and the locks on the lower Fox River has ceased operation. A marked navigation channel guides passage across the lake from the inflow of the Wolf River in the west (connecting to Lake Poygan), to the outflow of the Fox River east to Lake Winnebago, a remnant of the waterway. Lake Butte des Morts is popular among both fishermen and recreational boaters during the warm months, and with ice fishermen in the winter. U. S. Highway 41 (US 41) / Interstate 41 (I41) spans the east end of the lake via a bridge and causeway combination. The bridge includes the Tribal Heritage Crossing, a designated national trail, which is a portion of the Wiouwash State Trail. Terrell's Island is a DNR organized wetlands conservation project located on the south shore, enclosed by a breakwall that extends some distance into the lake.