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Humans can’t control how much freshwater the hydrological cycle produces. However, they can dramatically increase the amount of water that is available for people to drink. The problem of insufficient drinking water is caused not by a lack of worldwide water resources but by water management and distribution problems. These problems are often rooted in political, social, and economic issues—but they do have solutions.

Watershed management is one key way that communities can improve the quality, quantity, and reliability of their water resources. Controlling erosion and runoff are always central to good watershed management. This can be done in a variety of ways. Contour farming and terracing have been practiced in many rural areas of the world for millennia. In urban areas, collecting surface runoff can provide water for immediate use and also improve water quality by allowing sediments and attached contaminants to settle out prior to use or release downstream. Such collected water can also be allowed to filter into the Earth and increase groundwater resources.

More recently, humans are learning to harness natural systems, reproduce them, and even combine them with other technologies to promote better water quality. Natural systems such as vegetated riparian “buffer zones” and reconstructed wetlands have been used to protect water quality and to reduce sediment and streamflow variations in streams.

Lakes and reservoirs serve as large-scale, long-term water storage facilities. Collecting water in these bodies can help to mitigate seasonal and even annual variability in precipitation and water runoff. But reservoirs do have their drawbacks. Open water is subject to evaporation, and reservoirs are subject to sedimentation which reduces water storage capacity. There is a social cost to reservoirs if people must be moved because their homes are located on land that will be submerged. Reservoirs may also result in changes in water quality, create problems for fish passage and reproduction, and alter streamflow patterns.

Many communities manage both groundwater aquifers and surface water as one interconnected resource—which in fact they are. This practice is known as conjunctive use, and it can enable very efficient consumption of water resources. A typical strategy is to use more surface water when it is plentiful (wet seasons and wet years) and to use more ground water in times of shortage. However, conjunctive use can be much more complex. In some cases excess surface water or treated wastewater is returned underground to refill aquifer reserves for future use, either by natural seepage or injection wells, through a process called artificial recharge.

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