Water level
Madge Lake's hydrology remains fairly isolated even at its current water level. However, a heavily beaver-dammed creek allows the slow drainage of its waters to the north. Water level control structures at the creek outlet provides some control over the lake's water level. Lake water eventually enters Bear Head Lake at the north-eastern corner of Duck Mountain Provincial Park. Bear Head Lake is then in turn drained by Bear Head Creek, which continues north-east, crossing the Manitoba boundary, to join the Swan River on its journey to Swan Lake. Madge Lake is therefore part of the Swan River drainage basin, rather than the watershed of the nearby Assiniboine River.