In addition, state laws also often delegate standard setting, implementation, or enforcement duties to units of local government or conservation districts. Because of this great variation in approach, it is not possible to quantify nonpoint authorities or to classify them in mutually exclusive categories. Moreover, because these laws operate together, it is necessary to understand each state's entire program in order to assess its potential for using an enforceable mechanism to deal with particular conduct in a particular place. For example, a state may address in its forestry law conduct that is addressed in another state by a soil and water conservation district law. Or a state may address agricultural activities in riparian buffer zones or critical areas in ways that it does not address similar activities that are located at greater distances from identified waters, while another state imposes similar requirements across all agricultural lands.
Some general observations emerge from the study.
First, nearly all of the states have some general statutory authority to deal with nonpoint source discharges that can be shown to result in water pollution. Careful scrutiny of these laws is essential in assessing their utility in controlling nonpoint source pollution. General discharge prohibition laws come in two major types. Some states with this type of authority have adopted explicit statutory or regulatory exemptions for agriculture or forestry activities. In these states, however, the difficulty of proving a direct link between a particular discharge and the condition of a waterbody can be substantial, or at least expensive absent ongoing and extensive monitoring.