Water Supply, Land Use, and Urban Growth

The availability of a water supply does not determine the population growth or land use that will be supported by that supply. Water needs vary between uses and water may be reallocated from one use to another. The same amount of water needed to serve a low population at low densities will support a larger population at a higher density due to reduced outdoor use. A reallocation of water from agricultural to domestic and industrial use permits a greater population. Therefore it is not the availability of water supply or lack thereof that permits or constrains growth but rather the political decisions by cities and counties related to economics, social factors, and land use. Analysis shows that land-use projections represent a more reliable basis than population for the determination of future supplemental water requirements and the design of water distribution systems.