Use of Water Quality Models

The use of dual standards in water quality management, i.e., the effluent and water body limitations, leads to two different water quality management situations. In the first scenario the mandatory effluent limitations will be sufficient to achieve the water quality goals, in the second they are not. The former situation is characterized as effluent limited. The latter situation in which further actions beyond the mandatory effluent controls specified by the effluent limits are needed to achieve the water quality goals, is called water quality limited control. The economic mechanisms and incentives in either case are different. The effluent limited controls rely heavily and often exclusively on the “discharger pays” funding mechanisms while the water quality limited controls may require incentives, benefits transfers and some public financing.