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.
Agriculture is also the most water-intensive sector at the global level. According to the UN Food and Agriculture Organization (FAO), irrigation is responsible for about 70 percent of global water use, and a significant amount of water waste. According to the FAO, as much as 60 percent of water withdrawn for irrigation often does not reach the crop. A global reduction in agricultural water consumption of 15 to 20 percent would make more water available than all the water consumed in cities and industries today.
By helping nearby farmers consume less water more efficiently, cities could free up a new source of local water supply, improve the efficiency of water-use in agricultural production, and improve the overall efficiency of crop production. More efficient water use could, in turn, potentially improve the price and reliability of agricultural products, which could benefit farmers and consumers alike.
According to Water Policy, there is considerable opportunity and rationale for cities and farmers to form water partnerships. Cities depend on farmers for food, and farmers depend on cities for markets; some cities are struggling to access the water they need to sustain growing populations, and some farmers use a lot of water very inefficiently. Although there are legal, social, and technical hurdles associated with the development of urban-rural water conservation partnerships, the potential payoff is too big to ignore.
Does your community collaborate with farmers to increase water-use efficiency? Let us know in the comments section below.
Sophie Wenzlau is a Senior Fellow with the Worldwatch Institute.