This solution may be appropriate for a specific bounded water body such as a lake or reservoir, where there are a limited number of identified polluters (typically industrial companies, wastewater utilities or mines) whose discharges have a clearly identifiable impact on surface water quality. Polluting agents (firms, utilities, etc.) Polluters w'ould be allowed to buy and sell these licences. The total volume of licences could be reduced overtime with the aim of reducing overall pollution. The latter would save money by buying licences rather than undertaking abatement themselves. In time, the desired amount of pollution abatement would gravitate towards “efficient” polluters, at a lower cost to society compared to the situation where every firm was obliged to abate, whatever the cost.