Since the 1980s there has been growing public concern about water quality. Water pollutants are often classified as point source or non-point source pollutants. Point source pollutants are those that can be traced to a precise source, such as a pipe, ditch or containers. In agriculture there are relatively few point sources of water pollution although certain types of confinement livestock facilities and greenhouse facilities could qualify as point sources. Environmental policies initially concentrated on point source industriel pollution, but then attention shifted to non-point sources of surface and groundwater pollution. Agriculture is now perceived as the main polluter of the water supply. Hence governments seek to counter ecological damage from agricultural practices, and questions arise as to the types of policies to be implemented. One of the difficulties is that agriculture has its own specificities. First, prices are often subsidized (The Common Agricultural Policy (CAP) is an example for Europe) and stimulate production intensification. It is difficult to suggest a tax on agricultural products otherwise subsidized without having contradictory effects. Moreover, a tax on agricultural products has inevitable effects on the redistribution of revenues. Taxes applied on inputs related to pollution (fertilizers and pesticides) also have a strong income effect. Land is a fixed input, with price subsidies inducing intensification and a consequent higher price of land (rent). Higher prices induce an increasing use of chemical inputs.