This book investigates how actors organize in order to solve a water quality problem. Research on the use of environmental resources has mainly focused on the circumstances needed for users to self-organize or to maintain an already sustainable way of resource use. Few studies have investigated the reasons why actors start to cooperate when they are faced with an environmental problem. Actor networks in three regions of the Rhine catchment area are scrutinized regarding a) actors¿ cooperation pattern when managing an environmental problem; and b) the factors that trigger actors in a common-pool resource situation to initiate cooperation. Water quality policy is analysed in two European