The triennial UN World Water Development Report is a joint undertaking of 24 UN agencies comprising UN-Water in partnership with governments and other stakeholders, and coordinated by WWAP. Chapter 3, coordinated by the United Nations Human Settlements Programme (UN-HABITAT), focuses on the growing urban water supply and sanitation needs, particularly in lower- and middle-income countries, which face increasing competition with other sectors. Rising incomes in other portions of the world population fuel demand for manufactured goods and environmental services and amenities, all of which require water. This chapter emphasizes the scale of the growing urban water challenges, pointing out that nearly one-third of urban dwellers worldwide live in slums.