Selected Proceedings of the 1st IWA World Water Congress, held in Paris, France, 3-7 July 2000. The World Water Congress held in Paris in July 2000 was the first under the banner of the International Water Association, formed by the merger of the International Association on Water Quality and the International Water Services Association. The success of the merger was reflected in the unprecedented degree of interest and participation in the Congress, with nearly two-and-a-half thousand delegates attending for 450 oral presentations, 750 poster presentations and 4 workshops and seminars. From the large number of oral presentations, 41 have been selected for this issue. The first five highlight the work of the IWA Task Group that is devising the River Water Quality Model No 1; three papers set out key aspects of the model as it reaches its final form and two case studies show how the model can be implemented. Other papers selected cover the topics of: stormwater management; water resources management and protection including diffuse pollution; river basin management and organization; environmental restoration; and environmental engineering education. With authors who rank among the world's leading experts in these fields, tackling some of the most prominent contemporary problems, these proceedings are an essential compilation of the latest advances relating to the management of impacts on the water environment.