Available clean water is critical to the health of people, the environment, and the economy. Ecosystem such as rivers, lakes, and streams provide roughly 80 percent of usable freshwater, while the remaining water comes mostly from underground wells1.
Vegetated land cover helps regulate the flow of water through a watershed by intercepting, absorbing, and slowly releasing water. This “sponge” effect can reduce adverse impacts such as stream bank erosion, sediment transport, and the frequency and severity of floods and drought.
Natural resources such as wetlands, stream buffers, and vegetated land cover can also naturally filter out pollutants such as metals, pesticides, sediment, and overabundant nutrients that may affect water quality.
The efficiency of ecosystems to filter pollutants depends on many biological and physical characteristics, including species composition, soil types, slope, and climate characteristics.
Natural land cover helps maintain the flow and usability of water resources so that they remain clean and abundant for sustainable use by current and future generations.
Stressors to water quality and quantity
Multiple factors can affect water quality and quantity, including land management, point-source pollution, hydrologic alteration, and invasive species.
This eco-wheel image shows the natural resources providing clean and plentiful water, the benefits, and drivers of change.
Point-source pollution enters water directly from factories, power plants, and other stationary sources. Non-point source (NPS) pollution is pollution that runs into water from agricultural lands, impervious surfaces, or other land uses.
In the 2000 National Water Quality Inventory, agricultural NPS pollution was reported to be the leading source of water quality impairment in surveyed lakes and rivers2. Forestry practices also significantly affect water quality by increasing the amount of sediment that gets deposited into local water bodies.
Pollution reduces the overall usability of water, and in some cases, such as with the presence of algal blooms, can transform entire ecosystems.
Altering the hydrologic regime through activities such as dam construction interrupts the overall functionality of water systems by slowing water flow, trapping sediments, changing temperature, and promoting the presence of non-native and invasive species.
Invasive species may further undermine natural communities by crowding out native species in riparian areas, changing local species composition, and affecting structural integrity as well as the ecosystem’s ability to remove pollutants from the environment.
Various land uses, such as those that require large tracts of impervious surfaces (e.g., parking lots), also affect water quality and quantity. Impervious surfaces prevent rainwater from entering the soil, forcing water to flow along with the land until it finds a place to drain, which impedes groundwater recharge. These surfaces also increase the quantity, speed, and temperature of water runoff and add to water pollutant loads that can reduce water quality downstream.
Health impacts and benefits
Clean and plentiful water resources are needed for every aspect of life. Humans require safe, potable water for drinking, food preparation, and simple everyday uses.
Though most U.S. municipal water resources are typically treated before consumption, maintaining clean water resources helps minimize the need for and cost of this treatment. For instance, the New York City drinking water supply system is the largest unfiltered water supply in the U.S., which is made possible through strict watershed protection measures. This protected natural system has saved the state an estimated $8 – $10 billion in avoided water treatment costs4.
Municipal water sources are typically treated only for those contaminants that we are aware of, thus making natural filtration by ecosystems beneficial in adding a level of protection. Contaminated water that is not adequately treated may result in waterborne disease outbreaks or serious health issues as a result of chemical or metal contaminants.
Abundant water resources are used to grow crops, water feed animals, and process much of the food that we consume.
Water resources are also used to produce power (e.g., thermoelectric, hydroelectric, nuclear) and are essential to the production of most of the material goods that people enjoy.
Clean and abundant water resources are also needed for plant and animal survival. Wetland-dependent and aquatic species require aquatic habitats all or part of the year. These rivers, lakes, streams, and wetlands are also visually pleasing and provide opportunities for people to fish, hunt, and relax.
The regulating and filtration services provided by natural resources help maintain a clean and plentiful water supply for the entire nation.
