Abstract

Over the past century, cities in the arid western United States have relied on water from outside their local area to supply the needs of their growing populations. Urban Southern California relies on imported water from the Colorado River basin and northern California for approximately sixty percent of its total supply, the remainder coming primarily from local groundwater basins. The availability of imported water is declining due to environmental constraints and population growth in source areas and the effects of changing weather patterns on supply. As a result, water supply planners are looking to local sources to compensate for expected reductions in imported water, for example recycled wastewater, ocean desalination, and rainwater harvesting. This paper discusses the potential for achieving a sustainable urban water portfolio focused on local supplies, using metropolitan Southern California as an example. To accomplish this requires assessing how much water could be available if water conservation measures and local water sources were utilized to their fullest potential, and determining what sorts of changes – technological, managerial, and behavioral – might need to be implemented to bring this about. The question then is whether the region could manage without imported water in the future. Utilizing more local water sources in combination with conservation and efficiency measures will result in a water portfolio quite different from the current model, but one that appears to be achievable.