The aim of this work is to assess the impacts of the Oasis Project, a programme of payments for environmental services, on the operation of the Vila Regina Water Treatment Plant in the municipality of Apucarana. In the evaluation of the Oasis Project, the influence of turbidity on the consumption of chemical products for water treatment was verified, but it was not possible to quantify the benefits in terms of environmental services acquired by the conservation practices that have already begun since the implementation of the programme. It can be concluded that Payments for Environmental Services programmes such as the Oasis Project should focus on permanence, through changes in land use that are sustainable and resistant to different political and economic times, and should adopt a policy of cooperation between all entities. Partnerships between local, national and regional governments with companies and civil society can provide essential safety nets for the continuity of public policies.