Storm water, or constructed, wetlands represent one of several best managements practices commonly used to treat runoff water. They may have a strong impact on the quality of receiving waters, and therefore this impact needs to be taken into account when performing TMDL assessments. The hydrologic, biologic and chemical processes that occur within wetlands are very complex. These processes are both multi-layered as well as being intricate interwoven.

Attempts to predict wetland response is difficult because of the complex relationships involved. One approach to address the problem of response prediction is to apply models that account for many if not most of the processes present within the wetland system. Two- and three-dimensional models include spatial variations in the features of wetlands and, although complex to develop and apply, can represent much more accurately the different wetland cycles than one-dimensional models.