This guidance note aims to explain key sector features of urban water supply and identify entry points for mapping governance risks. The urban water supply sector is vulnerable to a broad range of risks that can threaten development effectiveness. Risks can spring from the involvement of multiple institutions in water governance, capital intensity, large-scale procurement contracts for goods and services that lend themselves to corruption, interface between public and private sectors, and political pressure on tariffs. Additional factors include weak capacity of sector agencies, high demand for water services, water scarcity, and dispersed water provision in poorly planned urban communities.