Northern Highlands Lake District, NE Wisconsin, Upper Peninsula, Michigan. The NHLD (ca. 5000 km2) contains more than 7500 lakes and 1500 streams. The region is situated along the southern extent of the boreal peatlands and was strongly affected by the retreat of glaciers between 10,000 and 12,000 years ago, which left approximately 30 - 50 m of sandy, noncalcareous till across the landscape. As a result of the porous nature of regional soils, groundwater flow, in addition to precipitation, is often an extremely important input to surface waters in the region. Lakes range from small dystrophic bog lakes less than 1 ha in area to systems greater than 2,500 ha, while streams range from small intermittent channels to large order systems such as the Wisconsin, Chippewa, and Wolf Rivers. Drainages within the NHLD flow either into the Mississippi River or the Laurentian Great Lakes. Land cover (2001 National Land Cover Data) is a predominantly a mix of deciduous and coniferous forest (52%), wetlands (28%), and lakes (13%).