The “Three Districts” is a public association of municipalities for managing and operating potable water and sewage networks in 32 cities. The organisation is the owner of the networks and related equipment and supervises private companies that undertake daily operations. The municipal organisation manages the water systems over a territory of 1500 km2. The organisation runs, according to the municipal legal code, technical, institutional, legal and financial services.

The Board owns a 750 km urban and rural drinking water network. They also own water treatment infrastructures, reservoirs and pumping stations. The operation of these systems, governed by the Public Service Delegation regime, is entrusted to an operator who is answerable to the organisation. This is an example of the application of a Public-Private Partnership mechanism (PPP).

The implementation of works (extension, restitution and modernisation) is subject to the public market legal code, derived from European environmental and water legislation (including WFD 2000/60/EC and Floods Directive 2007/60/EC). AETS gives the municipal organization its support for selecting and preparing investments in the network: wells, pumping stations, reservoirs and pipes. The levels of interventions are technical, financial and legal. In the water domain, particular attention is paid to quality criteria and specific technical provisions that define leakage prevention procedures. The Board equally fixes the price of water.

For the sanitation network, the rehabilitation works are permanently undertaken for extending and rehabilitating the networks: the increase of the number of users has had an increase of 34% in the last 3 years. For non-collective systems in rural areas, the organisation was the first to apply European rules in France and operates in accordance with the most modern and adapted schemes.

The Board is associated with other organisations for the management of long-distance water transportation. It also manages the following structure: Common Water Board for the Orthez Region (Syndicat Mixte des Eaux de la Région d’Orthez).