By Sophie Wenzlau
As world population grows, meeting the demand for clean freshwater can be a serious challenge, especially for arid and semi-arid cities such as Los Angeles and Dubai. According to a report published in Water Policy earlier this year, cities around the world are struggling to access the water they need to support continued growth.
According to UN Water, world population is projected to grow from 6.9 billion in 2010 to 8.3 billion in 2030 and to 9.1 billion in 2050. At the same time, urban population will increase by 2.9 billion, to a total of 6.3 billion in 2050, as a result of urban population growth and movement into urban centers. Growth in cities has led to a dramatic increase in urban water use; since 1950, global water use in cities has increased five-fold as a result of increasing domestic and industrial demand.
To meet the growing demand for water, many cities—such as San Antonio, Adelaide, Phoenix, and San Diego—have had to supplement the use of local water resources with significant water imports from major rivers or aquifers. As a result, urban water use has contributed to the depletion of many important freshwater sources, such as the Colorado, Yellow, and Amu Darya rivers, and resulted in significant ecological damage.
In response to increasing water scarcity, some cities are promoting innovation, efficiency, and conservation in water use. For example, the city of San Diego—which is largely dependent on the depleted Colorado River—has taken steps to promote conservative use of local water resources and decrease reliance on imported water by diversifying local water supplies. In San Diego, these measures have included the development of a water recycling system, a desalinization system, urban conservation policy, and, most notably, an urban-rural water conservation partnership in which the city compensates farmers in surrounding areas for implementing agricultural water conservation measures.
According to Water Policy, San Diego’s agricultural conservation partnership is an innovative model worthy of consideration by other cities, for “half of all cities with populations greater than 100,000 are located in water-scarce basins, and in these basins agricultural water consumption accounts for more than 90 percent of all freshwater depletions.” San Diego’s model is innovative in that it frees up water for metropolitan consumption by addressing inefficiencies in the region’s most water-intensive sector. According to the San Diego County Water Authority, agricultural conservation measures are expected to provide 37 percent of city water supply by 2020.