**4.2 Non-point source control**

In the USA, the Total Maximum Daily Load (TMDL) program is the current Stormwater Management (SWM) methodology used by the EPA to protect receiving water systems from stormwater pollution. A TMDL calculates the maximum amount of a pollutant that a water body can receive and still meet water quality standards. Once that calculation is made, pollutant allocations (point and nonpoint) are partitioned throughout all sectors allowing only enough pollutants into the river to maintain identified use. A similar program exists in Europe. River Basin Management Plans (RBMPs) are required documenting impairment from diffuse (non-point) sources and plans for improvement. The idea of pollutant loading identification and then curtailing influx to the river is the consensus for controlling this type of pollution. In fact, some level of SWM is considered an important environmental issue in countries worldwide regardless of their level of development [60].

Successful implementation of SWM requires installation of some type of green infrastructure, changes in land management or permit modifications. Other tools available include mitigation banking [61] and nutrient trading [62]. These tools work in concert with other options to create an economic blueprint to fund the needed reductions to meet SWM requirements.
