Record high water levels have caused many problems for Madison's lakes and residents in recent summers. Powerful storms send large volumes of fast-moving water down Pheasant Branch, toppling trees, eroding banks and depositing tons of sediment into the Conservancy wetlands and Lake Mendota. Flash flooding and highly erosive flows have intensified in recent years due to increasing development and loss of permeable surfaces in the Pheasant Branch watershed.
High water levels in the marsh make it easier for canoeists and kayakers to paddle over mud flats all the way to the springs. But then sediment-filled brown water cover the clear bubbling springs, making them difficult to see.
Some marsh plants and animals tolerate flooding conditions better than others. For many animals, timing is everything. For example, low water levels in March make it difficult for northern pike to enter the marsh for spawning, but high levels at just the right time allow carp to spawn in the marsh. Carp degrade water quality and habitat by uprooting native aquatic vegetation and stirring up sediments as they feed.
Many animals, like white-tailed deer and Sandhill Cranes, move to higher ground when the marsh floods. Mink and other aquatic animals easily adjust to varying water levels. But flooding is not so good for some species. Sedge Wrens that nest close to ground level in sedges or grasses may lose their young when nests were knocked over by floodwaters. The young of small mammals like meadow voles drown when their nests are flooded.
Some plants, like cattails, are experts at transporting oxygen from the air down to their flooded roots. Others are stressed or may die from long-duration flooding. Trees in lowland areas suffer such a fate when conditions are wetter than normal. The good news is that standing dead trees provide valuable habitat for cavity-nesting birds such as redheaded woodpeckers and woodducks.wood ducks.
Flooding also brings suspended sediments, nutrients and pollutants into the marsh and damage wetland plants like wild rice. A hundred years ago, wild rice was abundant in the marshes around Madison but the Pheasant Branch marsh if now one of the few places in southern Wisconsin where it still grows. This annual plant likes relatively clear water. Seedlings will die if their water is cloudy or levels rise too quickly as they are emerging to the surface.
Wild rice beds in Pheasant Branch marsh depend upon the Pheasant Branch springs to maintain water clarity. Although the marsh may not have wild rice when there is flooding and low water clarity, the plants will survive if flooding does not occur year after year.
Updated February 2006
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