The Definition of Water Sources
Your drinking water takes a long path before it arrives in your home. It comes from both surface water and ground water sources.
Water sources include lakes, streams, rivers, wetlands, springs and the ocean. They all participate in the natural hydrologic (water) cycle. Water is consumed by evaporation, transpiration and through consumptive uses.
Water from the Earth
Water falling from the sky in the form of rain or snow fills rivers and lakes, recharges aquifers and is drunk by plants and animals. Almost all of this water eventually drains to the ocean.
Most of the water on Earth is salty (97.5%), but some is fresh. Only 2.5% of all water is freshwater, and less than 1% is available to humans. The rest is frozen in glaciers and ice caps, or deep underground in aquifers.
Surface water sources include oceans, rivers and streams, lakes, reservoirs, and groundwater. Humans use surface water for drinking, manufacturing, and power generation and as a source of irrigation. Humans also create canals, dams, aqueducts, and wells to direct surface water where they need it. Commercial water use includes hotels, restaurants, office buildings, and other businesses. This water can be public-supplied, such as from a city water department or county water supply, or self-supplied, such as from a private well.
The water cycle is a continuous process in which water moves from the Earth to the atmosphere and back again. This cycle includes precipitation, runoff, infiltration, percolation, storage, evaporation, and transpiration. It also includes return flow (irrigation) and wastewater-treatment return flow. The water cycle is illustrated in the figure below. Water in the blue sphere is all the water on Earth, while the green sphere shows the amount of freshwater in rivers and lakes.
Water from the Sea
Seas are Earth’s largest bodies of water and contain saline water. Over time, dissolved materials from the ocean bottom and materials released from underwater volcanoes and hydrothermal vents have made the ocean salty. This process is called sedimentation.
Oceans also contain organic matter, including residues of dead organisms and organic waste from human activities such as agriculture and industry. This material provides a source of nitrogen, which helps plants grow and forms the basis for food chains that support living organisms. The presence of large amounts of nitrogen in the water can lead to algal blooms that use up oxygen and threaten human health and wildlife.
Water in the ocean is under atmospheric pressure and rises and falls as it flows through rivers and lakes. This movement is known as the water cycle.
Adaptation–Actions to manage natural and human systems in response to actual or expected impacts of climate change, such as increased frequency and intensity of drought, floods, storm surges, or other changes.
Water that is diverted from a surface stream or aquifer for use in homes, business and industrial facilities comes from either public-supplied sources (such as a county water department) or self-supplied sources (such as local wells).
Water that is reclaimed from wastewater treatment is returned to the environment through sewers and drains or is placed into storage reservoirs. It can also be reclaimed directly from the ground through injection wells, where it is pumped into aquifers that don’t contain drinking water or are at or below freshwater levels.
Water from the Air
Most of the water on Earth is in the air, forming clouds and precipitating as rain or snow. It is also present in the form of vapor (water evaporating from surfaces) and liquid water that forms droplets or coats solid particles, such as in fog. There is also some water ice in the atmosphere.
Water is a resource that provides us with many products, materials and resources for life. However, overuse of natural water supplies has resulted in the deterioration of water quality. The seepage of mineral fertilizers (phosphates and nitrates), pesticides, herbicides, and waste from industrial plants into lakes and rivers has made them unfit for drinking or other uses. The thermal pollution of the discharge of heated wastewater from nuclear-power plants, power stations, and industry also has caused significant deterioration of water quality.
A water source is a lake, stream, spring, groundwater supply, or other water body from which water is withdrawn to meet the needs of a public water system. It can be a single point or an area defined by topographic boundaries, or it can be the site of an intake or dam.
Water from the Ground
The water we drink comes from either public supplies provided by a city or county or from self-supplied sources such as private wells. About 13 million people in the United States get their drinking water from wells. Commercial and industrial water users also rely on ground water. In fact, about three-fourths of the fresh water withdrawn from the environment each year is used for irrigation, industry and other purposes.
Rain, spring melt or irrigation water seeps down through the soil to collect in void spaces between soil grains or cracks in bedrock. Such areas are called aquifers. Depending on the permeability of the rock and soil, ground water can travel quickly or slowly. It may accumulate in shallow aquifers near the surface or in deeper aquifers where it can flow back to surface water bodies.
Water in aquifers can be very salty or very fresh. It can also be very old (fossil water). Some ground water is recharged from surface waters, and some is recharged by underground movement of the Earth’s crust.
Some ground water seeps back into surface water bodies through streams, wetland marshes and lakes. This is known as a “gaining stream.” Most of the fresh water in streams, rivers and lakes originates as ground water. Other ground water is discharged from an aquifer to a surface stream or wetland through springs and wells. Because aquifer water often stays in contact with rock minerals for longer periods of time than stream water, it is usually more saline.
