Interspersed throughout the watershed are wetlands. Located in lowland areas, wetlands are comprised of unique vegetation and saturated soils during all or part of the year. Once disdainfully regarded as mosquito-infested swamps, today wetlands are appreciated for serving three essential functions. These include providing critical wildlife habitat, assisting with water purification, and helping to store water during storms and floods.

Wetland vegetation is uniquely suited to life in wet soil. For instance, some trees and bushes that live in this environment have very shallow root systems. Other plant species grow roots from their stems to absorb oxygen from the air. The diverse vegetation found in wetlands may include cottonwoods and willows, rushes, cattails, and grasses. The unique conditions found in wetlands are home to many plants and species that are not commonly found.

This lush vegetation is well suited for a diversity of species. Some species are drawn to wetlands to feed and rest, others visit as part of their migratory path, and still others find wetlands to be an ideal setting for reproduction. As such, wetlands are densely and diversely populated areas. Birds such as the yellow-headed blackbird and kingfisher flit amid the sedges. Ducks and geese make wetland marshes their nesting place. And species as diverse as the high-diving osprey, the muskrat, and voles and shrews can be found there.

Beyond providing valuable wildlife habitat, wetlands also perform less noticeable functions. Wetlands along rivers and flood plains help regulate stream flow by storing water during periods of high runoff and heavy rainfall. By slowly releasing the water back into the surrounding environment, the frequency, level, and velocity of floods and riverbank erosion are reduced.

Wetlands also provide a natural water filtration process. For example, they can trap sediments and filter metals and organic polluntants like sewage and agricultural waste. This cleansed water is then released back into springs, streams, and aquifers that feed the tributaries.