Across the world, the role and functionality of urban water utilities has evolved over time, in response to urban challenges. The role of the urban water sector in each region has generally begun with water supply, and then been followed by sewerage, drainage, environmental protection, and then water security efforts through the collection of alternative water sources, such as desalination and recycled water. Typically these services have been delivered through networks of underground pipes, and publicly inaccessible treatment facilities.