Urban Sprawl Is Associated with Reduced Access and Increased Costs of Water and Sanitation

Many cities are expanding in areas with scarce rainfall and limited water retention capacity, and are also becoming elongated and sprawled, making it harder to deliver services. This study quantifies the impact of urban form on access to water. We craft comparable urban forms for over 100 cities in Asia, Africa, and Latin America. For each city, we analyse the distance to the centre, one of the most critical features of cities. We introduce two metrics: remoteness, which quantifies the distance of any location to the city centre, and sparseness, a population-weighted average of all locations. We find that less remote areas have higher average income, are closer to critical infrastructure and have higher access to sewage and piped water. Sparser cities have higher water tariffs, lower proximity to critical infrastructure, and lower access to sewage and piped water. Finally, we model urban expansion under three scenarios: compact, persistent, and horizontal growth. When cities expand through compact growth rather than horizontal expansion, 220 million more people could gain access to piped water, and 190 million more to sewage services.