During the acute phase of an emergency the priority for humanitarian agencies is to rapidly establish water supply and other basic services (e.g. sanitation, hygiene, and solid waste) for people affected by disaster or crisis. However, the immediate response to an emergency is relatively short in duration, while the services, particularly water supply, often need to meet the needs of affected populations for many years. Often crises are protracted in nature and it is therefore important to understand how service performance evolves and whether service users are satisfied with the level of water supply. This is an important consideration because long-term sustainability may not represent an important part of initial thinking by humanitarian agencies. The United Nations High Commission for Refugees estimates the average time spent by a refugee in a camp is 10 years, while the average refugee camp remains for 26 years. Two questions arise: first, how will humanitarian agencies ensure emergency water supplies reach the desired performance levels; second, how will local institutions be able to manage, modify and finance the services that camp or settlement dwellers and host communities will depend upon. In this chapter the authors explore experiences from two country case studies and monitoring data extracted from ongoing humanitarian crises. The main conclusions are: service level enhancements are often slow to materialise and widespread efforts are required to raise performance levels.