In addition to the well-known programme for flood protection, Dutch water policy consists of two main subsectors; water supply and ground water protection, and surface water quality management. In this contribution special attention is paid to the characterisation of these subsectors using two network variables; mutual commitment and interrelatedness. The dynamics of change of these features and their relation with policy opportunities are examined. The water supply sector was amalgated into larger companies and developed more cooperation as a result of the pressure of the environmental challenge, which made it impossible to continue pumping and billing. Though the sector in a sense became more integrated, this was accompanied by an increased need to do business with other interests, such as agriculture. The surface water quality subsector also moved from a very integrated community into a more open structure. This openness is, however, to a large extent organised by the sector itself, by incorporating other interests in their councils and committees. Both subsectors increasingly adopt a consensual approach in dealing with these other interests.