Wetlands occur where water saturates the ground for a period of time on a regular basis. Some of Arizona's most important wetlands are dry much of the year. However, even the temporary presence of standing water can foster flood-adapted plants and develop unique, productive soils. Plants, such as wetland sedges and Arsene's buttercups, have co-evolved with seasonal wetlands. Wetland plants capture energy through photosynthesis that is shared throughout the ecosystem with insects, birds, and other wildlife. Wetlands also cycle nutrients very effectively.

A wetland is a radiating habitat, which means it sustains ever-widening circles of different plants and animals. More than 80% of wildlife species in Arizona depend on a wetland or streamside habitat at some point during their life cycles. Yet wetlands are very rare in Arizona. A map created by the University of Arizona shows that wetlands now occupy less than 1% of the state and are mostly in the mountainous central region. 

Wetlands are also important because they store floodwater and improve water quality. Did you notice that the Willow Bend parking lot is slightly slanted toward a culvert in its southeast corner? Rain and snowmelt flow through the culvert into the wetland, where flood-tolerant plants slow it down and allow suspended sediments to settle. Pollutants stick to soil particles; some are taken up by plants or transformed by microorganisms as the water percolates into the ground.

While a constructed wetland such as Willow Bend's is not as biodiverse as a natural one, nevertheless it sustains wildlife, captures floodwater, and improves water quality in its own small way. It also has educational value in countering a persistent view that wetlands are wastelands that should be drained and put to use.