13.3: Water Scarcity and Solutions (2024)

Dams and Reservoirs

Reservoirs(artificial lakes) that form behind dams in rivers can collect water during wet times and store it for use during dry spells (figure \(\PageIndex{b}\)). They also can be used for urban water supplies. Other benefits of dams and reservoirs are hydroelectricity, flood control, and recreation. Some of the drawbacks are evaporative loss of water in arid climates anddownstream river channel erosion. Additionally,dams reduce water flow downstream, which could lead to political conflicts when rivers span states or countries.

The negative ecosystem impacts of dams are another major drawback. For example, dams change a riverto a lake habitat and interfere with migration and spawning of fish. Furthermore, warming of the surface water in the reservior influences the temperature of the water downstream, impacting the fish and aquatic invertebrates that are adapted to colder water. Dams also trap sediments that would otherwise continue to flow down the river, creating habitat and supplying nutrietns downstream.

Rainwater Harvesting

Rainwater harvesting involves catching and storing rainwater before it reaches the ground. Figure \(\PageIndex{c}\) shows a complex rainwater harvesting system (rain water capture system) proposed for federal buildings, but smaller, simpler systems (sometimes called rain barrels)can be used by individual homeowners (figure \(\PageIndex{d}\)).

Aqueducts

Aqueducts can move water from where it is plentiful to where it is needed. Aqueducts can be controversial and politically difficult especially if the water transfer distances are large. One drawback is the water diversion can cause drought in the area from where the water is drawn. For example, Owens Lake and Mono Lake in central California began to disappear after their river flow was diverted to the Los Angeles aqueduct (figure \(\PageIndex{e}\)). Without water supply, Owens Lake dried and became a major source ofparticulate matter, polluting the air during dust storms (see Air Pollution).Owens Lake remains almost completely dry, but Mono Lake has recovered more significantly due to legal intervention. Learn more about the Los Angeles Aqueduct here.

Desalination

One method that can actually increase the amount of freshwater on Earth is desalination, which involves removing dissolved salt and minerals from seawater or saline groundwater (figure \(\PageIndex{f}\)). An advantage of this approach is that there is a virtually unlimited supply of saltwater. There are several ways to desalinate seawater including boiling, filtration, electrodialysis (applying an electric current to removed the ions which comprise salts), and reverse osmosis (figure \(\PageIndex{g}\)). All of these procedures are moderately to very expensive and require considerable energy input, making the water produced much more expensive than freshwater from conventional sources. In addition, the process creates highly saline wastewater, which must be disposed of and creates significant environmental impact. Desalination is most common in the Middle East, where energy from oil is abundant but water is scarce.

Water Reuse (Water Recycling)

Water recycling refers to reusing water for appropriate purposes such as agriculture, municipal water supply, industrial processes, and environmental restoration (figure \(\PageIndex{h}\)). This could occur at the scale of a single household, for example, installing plumbing that reroutes water drained from the sink toflush the toilet. Water recycling can also occur at large scales. For example, wastewater fromthe sewage system is regularly treated to an extent, but it can be treated further to producepotable water (which is safe to drink) and then pumped into depleted aquifers. This approach limits saltwater intrusion of aquifers near the coastand reduces dependence on precipitation and subsequent infiltration to recharge aquifers. Orange County Water District in California employed this system following an information campaign to explain the purification process and ensure public confidence in the safety of the treated wastewater.

Water Conservation

Water conservationrefers tousing less water and using it more efficiently. Around the home, conservation can involve both water-saving technologies and behavioral decisions. Examples of water-saving technologies include high-efficiency clothes washers and low-flow showers and toilets. Water-conserving behaviors include turning off the water while you brush your teeth, taking shorter showers and showers instead of baths, and fixing leaky faucets. A dishwasher uses less water than washingdishes by hand, particularly the dishwasher is only run when it is full. Similarly, running fewer, larger loads of laundry conserves water relative to more frequent, smaller loads. Choosing foods with a low water footprint (like eggs) over those with a high water footprint (like beef) can also conserve water.

Gardening offers several water-saving opportunities. If you live in a dry climate, consider growing only native, drought-tolerant vegetation, which requires little irrigation (figure \(\PageIndex{h}\)). When you do irrigate your garden, do so only as needed and early in the morning, when less water will be lost to evaporation. Drip systems assist in delivering only the needed amount of water in a way that minimizes evaporation. These strategiescan also be applied at large scales in agriculture,which is extremely important considering the high agricultural demands onour water supply relative to municipal use. Water conservation strategies in agriculture include growing crops in areas where the natural rainfall can support them, more efficient irrigation systems such as drip systems, and no-till farming, whichreduces evaporative losses by covering the soil.

Bottled water is not a sustainable solution to the water crisis. Bottled water is not necessarily any safer than the U.S. public water supply, it costs on average about 700 times more than U.S. tap water, and every year it uses approximately 200 billion plastic and glass bottles that have a relatively low rate of recycling. Compared to tap water, it uses much more energy, mainly in bottle manufacturing and long-distance transportation. (Purchasing a water filter is a more sustainable solution than bottled water if you do not like the taste of tap water.)