Possible Solutions for Meeting Water Demand in Stressed Regions
There are a number of possible methods to enhance supplies of fresh water, each of which has an economic, political, and/or environmental impact.
1. Provide three examples of potential ways to increase fresh water supplies.
ANSWER: Answers may vary. There are a number of potential strategies, including 1) Build large dams to increase water storage; 2) Bank water in groundwater storage; 3) Encourage transfers from other consumptive uses and/or conservation; 4) Increase recycling and reuse of wastewater; 5) Desalination of seawater or shallow saline groundwater.
Some of these strategies have been alluded to previously (e.g., encouraging transfers from agricultural use to drinking water supplies). Water storage behind dams is an old strategy and problematic in a number of ways (see Module 6), including high costs, environmental impacts, and political issues that arise when major rivers flow through multiple countries. Nonetheless, there is still major proposed and ongoing dam building in China and other countries.
Groundwater banking is a newer strategy that requires replenishment of aquifers with treated wastewater and/or with runoff available during times of excess. Costs are associated with treating, impounding, and injecting the water (see Module 7). This will mainly benefit regions with significant groundwater resources.
Recycling and reuse are gaining support with successful projects in the U.S. and elsewhere. Penn State University recycles and reinjects nearly 98% of its treated wastewater and has done so since the 1960s. Orange County, CA, has another successful system (see Module 8). Such systems must overcome consumer opposition, however, because of the perception that consumers will be drinking, well, toilet water! Nonetheless, the water quality in such systems is as good or better than that in municipalities that draw water from rivers downstream from other municipalities that discharge treated wastewater into the same river. Another form of reuse is to employ "gray" water (only partially treated) for irrigation of golf courses in arid to semiarid, water-stressed regions. Las Vegas, NV, has implemented such a system, coupled with the removal of water-hungry turf, for which the economics work and conservation is encouraged.
Desalination may be a last resort because of the costs of energy required to remove salts from seawater or water pumped from saline aquifers in non-coastal regions. However, in water-poor but hydrocarbon-rich middle-Eastern countries the economics may support the desalination of seawater. Alternative energy sources (e.g., solar) or emerging processes such as chemical reverse osmosis may be economical in the future as they become more efficient and less costly. And, of course, if water is deemed to have significant value in the future, the high costs may be more acceptable.
Finally, there are still proposals to import or export water from regions replete with fresh water resources (e.g. Alaska) to severely water-stressed regions (e.g. India). However, the costs of transporting such a commodity across the oceans would appear to exceed the value of that water at its terminus.
All of these strategies will be explored in later modules in more detail.