Our World in Data: https://ourworldindata.org/grapher/average-precipitation-per-year?time=1996#reuse-this-work

River Discharge Colorado River, U.S.. Rivers are part of overland flow in the water cycle and an important surface
water resource. Source Colorado River Basin map. https://www.usgs.gov/media/images/colorado-river-basin-map 

Lakes can also be an excellent source of fresh water for human use. They usually receive water from surface runoff and groundwater discharge. They tend to be short-lived on a geological time-scale because they are constantly filling in with sediment supplied by rivers. Lakes form in a variety of ways including glaciation (Great Lakes, North America, recent tectonic uplift (Lake Tanganyika, Africa), and volcanic
eruptions (Crater Lake, Oregon). People also create artificial lakes (reservoirs) by damming rivers. Large changes in climate can result in
major changes in a lake’s size. As Earth was coming out of the last Ice Age about fifteen thousand years ago, the climate in the western U.S. changed from cool and moist to warm and arid, which caused more than100 large lakes to disappear. The Great Salt Lake in Utah is a remnant of a much larger lake called Lake Bonneville.

 Lake Superior, the largest of the Great Lakes, has a water surface area of 82,100 sq km and a maximum depth of 406 m. The surface of Lake Superior is large enough to contain the land area of the states of Connecticut, Delaware, Hawaii, Maryland, and New Jersey combined. Lake Huron is the second in size with 59,700 sq km; Lake Michigan, third, with 57,750 sq km; and Lake Erie, fourth, with 25,700 sq km. These lakes provide important water connections between these ports of Michigan, and between these ports and other ports of the United States, as well as of the world. The four lakes represent a freshwater resource for domestic and industry use for many communities along the coast and those that can be reached by pipelines. The commercial fishery resources of the lakes are considerable but have been decreasing in recent years. Fishing for coho and chinook salmon, first introduced into the lakes in 1966 is now a major sports activity on the lakes and in the adjoining rivers. Commercial fishing is handicapped by the fact that there is too high a concentration of undesirable chemicals in a number of fish species, particularly the salmon and lake trout. The Great Lakes hold 21% of the world’s surface fresh water. Lakes are an important surface water resource. Source : https://project.geo.msu.edu/geogmich/watershed.html

Although glaciers represent the largest reservoir of fresh water, they generally are not used as a water source because they are located too far
from most people (see Figure Mountain Glacier in Argentina). Melting glaciers do provide a natural source of river water and groundwater. During the last Ice Age there was as much as 50% more water in glaciers than there is today, which caused sea level to be about 100 m lower. Over the past century, sea level has been rising in part due to melting glaciers. If Earth’s climate continues to warm, the melting glaciers will cause an additional rise in sea level.

A tourist boat approaches the face of the Perito Moreno glacier, a part of the Southern Patagonian Ice Field, where it feeds into Lago, Argentina. Credit: David Silverman/Getty Images

https://www.scientificamerican.com/article/mountain-glaciers-have-less-ice-than-previously-thought/

By Chelsea Harvey, E&E News on February 8, 2022

Although most people in the U.S. and the world use surface water, groundwater is a much larger reservoir of usable fresh water, containing
more than 30 times more water than rivers and lakes combined. Groundwater is a particularly important resource in arid climates, where
surface water may be scarce. In addition, groundwater is the primary water source for rural homeowners, providing 98% of that water demand in the U.S.. Groundwater is water located in small spaces, called pore space, between mineral grains and fractures in subsurface earth materials (rock or rivers or lakes except where there are caves, which are relatively rare. Between the land surface and the depth where there is groundwater is the unsaturated zone, where pore spaces contain only air and water films on mineral grains (see Figure Subsurface Water Terminology). Below the unsaturated zone is the saturated zone, where groundwater completely fills pore spaces in earth materials. The interface between the unsaturated zone and saturated zone is the water table. Most groundwater originates from rain or snowmelt, which infiltrates the ground and moves downward until it reaches the saturated zone. Other sources of groundwater
include seepage from surface water (lakes, rivers, reservoirs, and swamps), surface water deliberately pumped into the ground, irrigation, and
underground wastewater treatment systems, i.e., septic tanks. Recharge areas are locations where surface water infiltrates the ground rather than running off into rivers or evaporating. Wetlands and flat vegetated areas in general are excellent recharge areas. Groundwater is the name for water in the saturated zone and soil moisture describes water in the unsaturated zone. Therefore, groundwater is the underground water resource used by society but soil moisture is the principal water supply for most plants and is an important factor in agricultural productivity.

Subsurface Water Terminology Groundwater in pore spaces and fractures of Earth materials, saturated zone, unsaturated zone, and
water table, which follows land surface but in a more subdued way. Source: United States Geological Survey

Groundwater is in constant motion due to interconnection between pore spaces. Porosity is the percentage of pore space in an Earth material and it gives a measure of how much groundwater an Earth material can hold. Permeability is a measure of the speed that groundwater can flow through an Earth material, and it depends on the size and degree of interconnection among pores. An Earth material that is capable of supplying groundwater from a well at a useful rate—i.e., it has relatively high permeability and medium to high porosity—is called an aquifer. Examples of aquifers are Earth materials with abundant, large, well-connected pore spaces such as sand, gravel, uncemented sandstone, and any highly fractured rock. An Earth material with low hydraulic conductivity is an aquitard. Examples of aquitards include clay, shale (sedimentary rock with abundant clay), and igneous and metamorphic rock, if they contain few fractures.

As discussed above, groundwater flows because most Earth materials near the surface have finite (nonzero) porosity and permeability values. Another reason for groundwater movement is that the surface of the water table commonly is not completely flat but mimics the topography of the land surface, especially in humid climates. There is "topography" to the water table because groundwater moves slowly through rock and soil, so it builds up in higher elevation areas. In fact, when groundwater flows slowly through aquitards and deep underground, it can take many thousands of years to move relatively short distances. An unconfined aquifer has no aquitard above it and, therefore, it is exposed to the atmosphere and surface waters through interconnected pores (See Figure Flowing Groundwater). In an unconfined aquifer, groundwater flows because of gravity to lower water table levels, where it eventually may discharge or leave the groundwater flow system. Discharge areas include rivers, lakes, swamps, reservoirs, water wells, and springs . A spring is a water resource formed when the side of a hill, a valley bottom or other excavation intersects groundwater at or below the local water table, below which the subsurface material is saturated with water. A spring is the result of an aquifer being filled to the point that the water overflows onto the land surface. They range in size from intermittent seeps, which flow only after much rain, to huge pools flowing hundreds of millions of gallons daily. Springs are not limited to the Earth's surface, though. Recently, scientists have discovered hot springs at depths of up to 2.5 kilometers in the oceans, generally along mid-ocean rifts (spreading ridges). The hot water (over 300 degrees Celsius) coming from these springs is also rich in minerals and sulfur, which results in a unique ecosystem where unusual and exotic sea life seems to thrive. Springs may be formed in any sort of rock. Small ones are found in many places. In Missouri, the largest springs are formed in limestone and dolomite in the karst topography of the Ozarks. Both dolomite and limestone fracture relatively easily. When weak carbonic acid (formed by rainwater percolating through organic matter in the soil) enters these fractures it dissolves bedrock. When it reaches a horizontal crack or a layer of non-dissolving rock such as sandstone or shale, it begins to cut sideways. As the process continues, the water hollows out more rock, eventually admitting an airspace, at which point the spring stream can be considered a cave. This process often takes tens to hundreds of thousands of years to complete.

A confined aquifer is bounded by aquitards below and above, which prevents recharge from the surface immediately above. Instead, the major recharge occurs where the confined aquifer intercepts the land surface, which may be a long distance from water wells and discharge areas (see Figure Schematic Cross Section of Aquifer Types). Confined aquifers are commonly inclined away from recharge areas, so groundwater in a confined aquifer is under greaterthan- atmospheric pressure due to the weight of water in the upslope direction. Similar to river discharge, groundwater discharge describes the volume of water moving through an aquifer over time. Total groundwater discharge depends on the permeability of the earth material, the pressure that drives groundwater flow, and the size of the aquifer. It is important to determine groundwater discharge to evaluate whether an aquifer can meet the water needs of an area.

Blue lines show the direction of groundwater in unconfined aquifers, confined aquifers, and
confining beds. Deep groundwater moves very slowly especially through low permeability layers.

Source:https://www.usgs.gov/special-topics/water-science-school/science/groundwater-flow-and-water-cycle

Rainbow Springs, Florida, USA Source: https://www.usgs.gov/special-topics/water-science-school/science/springs-and-water-cycle

The illustration shows an artesian well and a flowing artesian well, which are drilled into a confined aquifer, and a water table well, which is drilled into an unconfined aquifer. Also shown are the Piezometric surface in the confined aquifer and the impermeable, confining layer between the confined and unconfined aquifer. Source: https://www.usgs.gov/special-topics/water-science-school/science/aquifers-and-groundwater

Artesian wells can be sometimes flow to the land surface naturally because of underground pressure.

This diagram shows a conceptual aquifer system having both unconfined and confined aquifers. Generally, the upper layer of an aquifer system is the unconfined aquifer, which does not have a confining layer of solid material above it. The top altitude of this aquifer is called the "water table", below which the ground and rock has all the spaces and voids full of water. Water from this aquifer must be pumped out in a well to get to the land surface.

In some locations there can exist confined aquifers below the unconfined aquifers. These confined aquifers have layers of solid material above and below them and are thus under pressure from the rock weight. As this diagram shows, for water to recharge these aquifers, it much seep down from the surface at a distance away and travel somewhat horizontally into the confined aquifer.

Wells that tap these confined aquifers are "artesian wells". If altitude that the pressurized aquifer pushes water up a well tapping it is the "piezometric level". If this level is below the land surface altitude (right side artesian well in the diagram) the water will not shoot out of the well at the land surface...the well is called an artesian well. But if the piezometric level is higher than the well head altitude at the land surface (the left side artesian well in the diagram above), the water will be pushed upward in the well and emerge at the land surface, with no pump needed. This kind of well is a flowing artesian well.

Groundwater in aquifers between layers of poorly permeable rock, such as clay or shale, may be confined under pressure. If such a confined aquifer is tapped by a well, water will rise above the top of the aquifer and may even flow from the well onto the land surface. Water confined in this way is said to be under artesian pressure, and the aquifer is called an artesian aquifer. Flowing artesian well in Brunswick, Georgia, USA Source: https://www.usgs.gov/media/images/flowing-artesian-well-brunswick-georgia-usa 

A confined aquifer tends to be depleted from groundwater pumping more quickly than an unconfined aquifer, assuming similar aquifer properties and precipitation levels. This is because confined aquifers have smaller recharge areas, which may be far from the pumping well. However, an unconfined aquifer tends to be more susceptible to pollution because it is hydrologically connected to the surface, which is the source of most pollution.

Schematic showing a cone of depression around the well, usually the result of overpumping.
Credit: Tara Gross, USGS https://www.usgs.gov/special-topics/water-science-school/science/aquifers-and-groundwater

Groundwater and surface water (rivers, lakes, swamps, and reservoirs) are strongly interrelated because both are part of the same overall resource. Major groundwater removal (from pumping or drought) can lower the levels of surface water and vice versa. We can define two types of streams: gaining (effluent) streams and losing (influent) streams.Streams either gain water from inflow of ground water (gaining stream; Figure 12A) or lose water by outflow to ground water (losing stream; Figure 12B). Many streams do both, gaining in some reaches and losing in other reaches. Furthermore, the flow directions between ground water and surface water can change seasonally as the altitude of the ground-water table changes with respect to the stream-surface altitude or can change over shorter timeframes when rises in stream surfaces during storms cause recharge to the streambank. Under natural conditions, ground water makes some contribution to streamflow in most physiographic and climatic settings. Thus, even in settings where streams are primarily losing water to ground water, certain reaches may receive ground-water inflow during some seasons.

Losing streams can be connected to the ground-water system by a continuous saturated zone (Figure 12B) or can be disconnected from the ground-water system by an unsaturated zone (Figure 12C). An important feature of streams that are disconnected from ground water is that pumping of ground water near the stream does not affect the flow of the stream near the pumped well.

Figure 12. Interaction of streams and ground water. (Modified from Winter and others, 1998.)

Gaining streams (A) receive water from the ground-water system, whereas losing streams (B) lose water to the ground-water system. For ground water to discharge to a stream channel, the altitude of the water table in the vicinity of the stream must be higher than the altitude of the stream-water surface. Conversely, for surface water to seep to ground water, the altitude of the water table in the vicinity of the stream must be lower than the altitude of the stream surface. Some losing streams (C) are separated from the saturated ground-water system by an unsaturated zone. Source: https://pubs.usgs.gov/circ/circ1186/html/gw_effect.html

Comal Springs
The highly productive Edwards aquifer, the first aquifer to be designated as a sole source aquifer under the Safe Drinking Water Act, is the source of water for more than 1 million people in San Antonio, Texas, some military bases and small towns, and for south-central Texas farmers and ranchers. The aquifer also supplies water to sustain threatened and endangered species habitat associated with natural springs in the region and supplies surface water to users downstream from the major springs. These various uses are in direct competition with ground-water development and have created challenging issues of ground-water management in the region. (Photograph by Robert Morris, U.S. Geological Survey (https://pubs.usgs.gov/circ/circ1186/html/gw_effect.html ).

Water Use in the U.S 

People need water to produce the food, energy, and mineral resources they use—commonly large amounts of it. Consider, for example, these
approximate water requirements for some things people in the developed world use every day: one tomato = 3 gallons; one kilowatt-hour of electricity (from a thermoelectric power plant) = 21 gallons; one loaf of bread = 150 gallons; one pound of beef = 1,600 gallons; and one ton of steel = 63,000 gallons. Human beings require only about 1 gallon per day to survive, but a typical person in a U.S. household uses approximately 100 gallons per day, which includes cooking, washing dishes and clothes, flushing the toilet, and bathing.

The water demand of an area is a function of the population and other uses of water. There are several general categories of water use, including off-stream use, which removes water from its source, e.g., irrigation, thermoelectric power generation (cooling electricity-producing equipment in fossil fuel, nuclear, and geothermal power plants), industry, and public supply; consumptive use, which is a type of off-stream use where water does not return to the surface water or groundwater system immediately after use, e.g., irrigation water that evaporates or goes to plant growth; and instream use, which is water used but not removed from a river, mostly for hydroelectric power generation. The relative size of these three categories are instream use >> off-stream use > consumptive use. In 2005, the U.S. used approximately 3,300 billion gallons per day for instream use, 410 billion gallons per day for off-stream use, and 100 billion gallons per day for consumptive use. The major off-stream uses of that water were thermoelectric (49%), irrigation (31%), public supply (11%), and industry (4%, see Figure Trends in Total Water Withdrawals by Water-use Category, 1950-2005). About 15% of the total water withdrawals in the U.S. in 2005 were saline water, which was used almost entirely for thermoelectric power generation. Almost all of the water used for thermoelectric power generation is returned to the river, lake, or ocean from where it came but about half of irrigation water does not return to the original source due to evaporation, plant transpiration, and loss during transport, e.g., leaking pipes. Total withdrawals of water in the U.S. actually decreased slightly from 1980 to 2005, despite a steadily increasing population. This is because the two largest categories of water use (thermoelectric and irrigation) stabilized or decreased over that time period due to better water management and conservation. In contrast, public supply water demand increased steadily from 1950 (when estimates began) through 2005. Approximately 77% of the water for off-stream use in the U.S. in 2005 came from surface water and the rest was from groundwater.

Distribution of points of diversion (PODs) and places of use (POUs) across water use categories and states. The numbers following the category names in the legend indicate the number of unique POD and POU coordinates for each category. The map shows 353,694 unique points from which 335,355 pairs are PODs and 10,563 are POUs and 7,776 are both PODs and POUs, though this represents only a portion of United States Water Withdrawals (USWWD) records, as many lack spatial coordinates. Hatched states have no data, while gray states have USWWD records but do not have associated spatial coordinates. Credit: Scientific Data (2025). DOI: 10.1038/s41597-025-06300-1

About 224,000 million gallons of freshwater are used every day for irrigation (48%), public supply (16%), and thermoelectric power (36%).

An understanding of where, when, why, and how much water is extracted for human use is fundamental to understanding the Nation's water availability.

Around 90% of daily water use in the United States goes toward:

• Crop irrigation
• Thermoelectric power plants, where freshwater is used in the process of creating energy
• Public supply, where water is withdrawn or purchased by a water supplier and delivered to many users

These three uses add up to 224,000 million gallons of freshwater per day.¹ In addition, saline water used at thermoelectric power plants adds another approximately 21,000 million gallons of water per day.

Average daily water use from 2010 to 2020

Millions of gallons used per day by use type

Trends in total water withdrawals, 1950-2015

This chart shows the trends in freshwater and saline-water withdrawals for the Nation from 1950 to 2015. What is remarkable about this chart is that it shows that the Nation's water use peaked in 1980 and has been fairly steady since then. Many of the stresses for greater water use have risen since 1980, such as population, the need to grow more food (irrigation), more industry, etc, yet total water use has not risen. This shows that water conservation efforts and greater efficiencies in using water have had a positive effect in the last 35 year

Trends in total freshwater withdrawals by source, 1950-2015

This chart shows the trends in surface-water, groundwater, and total-water withdrawals for the Nation from 1950 to 2015. Notice how the relative amounts of surface- and groundwater withdrawals (in percentages) has remained fairly constant. About three-fourths of the water used in America comes from surface water.

Trends in estimated use of water in the United States, 1950-2015

The water crisis refers to a global situation where people in many areas lack access to sufficient water or clean water or both. This section describes the global situation involving water shortages, also called water stress. The next section covers the water crisis involving water pollution.

Countries with water threat in 1995 and predicted water-stress countries in 2025. Water stress is defined as having a high percentage of water withdrawal compared to total available water in the area. Source:
Philippe Rekacewicz (Le Monde diplomatique), February 2006.

Water insecurity realities 

More than 2.2 billion people globally lack access to safely managed drinking water (United Nations, 2019), while millions of people in the United States are without clean, reliable water, lack basic plumbing, or rely on water systems with Safe Drinking Water Act violations. 

Today, the Human Right to Water is formally recognized by the United Nations, the State of California, and dozens of global businesses. Yet, the United States as a whole has yet to recognize the Human Right to Water or meet the United Nations Sustainable Development Goals for clean water and sanitation (SDG 6), climate action (SDG 13), or reduced inequalities (SDG 10). Source : Pacific Institute https://pacinst.org/our-focus-areas/

Case Study #1: The Colorado River

Learning Objectives:

1. Explain the importance of the Colorado River to the southwestern United States.
2. Identify the factors contributing to water shortages in the Colorado River Basin.
3. Describe the environmental, economic, and social impacts of reduced river flows.

The Colorado River is one of North America's most important rivers. Originating high in the Rocky Mountains of Colorado, it flows approximately 1,450 miles (2,330 km) through seven U.S. states—Colorado, Wyoming, Utah, New Mexico, Arizona, Nevada, and California—before reaching Mexico. Although the river drains a watershed that covers nearly 246,000 square miles (637,000 km²), it flows through one of the driest regions in North America.

The Colorado River supplies drinking water to about 40 million people, irrigates approximately 5.5 million acres of farmland, supports numerous Native American Tribes, generates hydroelectric power, and sustains nationally significant ecosystems and recreation areas.

Image: USGS Colorado River Basin November 3, 2016

What is the importance of the Colorado River

The river provides water for:

• Municipal drinking water
• Agricultural irrigation
• Hydroelectric power generation
• Manufacturing and industry
• Recreation and tourism
• Wildlife habitat
• Tribal communities
• National parks

What Major cities rely on the Colorado River?

• Las Vegas, Nevada
• Phoenix, Arizona
• Tucson, Arizona
• Los Angeles, California
• San Diego, California
• Denver, Colorado (through transmountain diversions)

The current problem of the Colorado River: For decades, demand for Colorado River water has exceeded the river's average annual flow.

Several factors contribute to the growing water crisis.

1. Overallocation

When the Colorado River Compact was signed in 1922, river flows were estimated during an unusually wet period. Water rights were allocated assuming more water was available than the river typically produces over the long term.

2. Population Growth

The southwestern United States has experienced rapid population growth over the past several decades.

Growing cities require increasing amounts of water for:

• Homes
• Businesses
• Parks
• Industry

3. Agriculture

Agriculture accounts for approximately 70–80% of Colorado River water use.

Major crops include:

• Alfalfa
• Cotton
• Lettuce
• Citrus
• Hay
• Vegetables

Some of these crops require large amounts of irrigation i.e. water in an area that is an arid climate.

4. Climate Change

Climate change has intensified drought conditions by:

• Reducing mountain snowpack
• Increasing evaporation
• Producing warmer temperatures
• Altering seasonal runoff patterns

Scientists estimate that average river flows have declined significantly over the past two decades due in part to rising temperatures and prolonged drought.

5. Environmental Impacts

Reduced river flows have affected ecosystems throughout the basin.

Impacts include:

• Loss of riparian habitats
• Declining fish populations
• Reduced wetland areas
• Increased wildfire risk
• Lower water quality
• Habitat fragmentation

Historically, the Colorado River formed an extensive delta in Mexico before reaching the Gulf of California. Today, the river often no longer reaches the sea because nearly all of its water is diverted for human use.

The Colorado River's two largest man-made reservoirs are:

• Lake Mead
• Lake Powell

These reservoirs provide:

• Water storage
• Flood control
• Hydroelectric power
• Recreation

During prolonged drought, water levels have declined dramatically, reducing both water storage capacity and hydroelectric power generation.

6. Sustainability Challenges

Balancing water demands among competing users remains difficult because stakeholders often have different priorities.

Examples include:

• Cities need reliable drinking water.
• Farmers depend on irrigation for food production and livelihoods.
• Hydroelectric facilities require sufficient reservoir levels.
• Tribal Nations seek fulfillment of water rights and protection of culturally significant resources.
• Wildlife depends on healthy rivers and wetlands.
• Recreation and tourism support local economies.

Effective water management requires cooperation, scientific research, and adaptive policies that respond to changing environmental conditions.

7. Looking Ahead

The Colorado River illustrates one of the most significant water management challenges in North America. Population growth, climate change, prolonged drought, and historical water allocations have created increasing pressure on a limited freshwater resource.

Future solutions will likely include expanded conservation efforts, improved irrigation technologies, greater water reuse, enhanced interstate collaboration, and continued protection of aquatic ecosystems.

The Colorado River demonstrates that sustainable water management requires balancing environmental protection with economic development and human needs.

Review Questions: 

1. Why is water considered essential for all living organisms?
2. Approximately what percentage of Earth's water is freshwater?
3. List four important functions water performs in living organisms.
4. Should access to clean drinking water be considered a basic human right? Explain.
5. Which poses a greater threat to freshwater resources—water pollution or water scarcity? Support your answer with evidence.
6. Should AI companies disclose water use for every data center?
7. How should communities balance economic development with protection of local water resources?

Critical Thinking

Imagine you are a member of a Colorado River water management commission. Water supplies are expected to decline by another 15% over the next decade. Develop a plan that balances the needs of cities, agriculture, Tribal Nations, hydropower generation, recreation, and ecosystem protection. Explain the trade-offs involved in your decisions.

How does the growth of AI illustrate the connection between water, energy, and sustainability?

The Colorado River Compact at 100

Case Study #2: The Aral Sea: One of the World's Greatest Environmental Disasters

Learning Objectives:

After completing this case study, students should be able to:

• Describe the historical importance of the Aral Sea.
• Explain how human activities caused the dramatic shrinkage of the Aral Sea.
• Identify the environmental, economic, and health consequences of the Aral Sea's decline
• Apply principles of sustainable water resource management to prevent similar environmental disasters.

The Aral Sea is a lake located east of the Caspian Sea between Uzbekistan and Kazakhstan in central Asia (see Figure Map of Aral Sea Area). This area is part of the Turkestan desert, which is the fourth largest desert in the world; covering approximately 68,000 square kilometers (26,300 square miles).It is produced from a rain shadow effect by Afghanistan's high mountains to the south. Due to the arid and seasonally hot climate there is extensive evaporation and limited surface waters in general. Summer temperatures can reach 60° C (140° F)! The water supply to the Aral Sea is mainly from two rivers, the Amu Darya and Syr Darya, which carry snowmelt from mountainous areas. In the early 1960s then-Soviet Union, diverted the Amu Darya and Syr Darya Rivers for irrigation of one of the driest parts of Asia to produce rice, melons, cereals, and especially cotton. The Soviets wanted cotton or “white gold” to become a major export. They were successful and today Uzbekistan is one of the world's largest exporters of cotton. Unfortunately this action essentially eliminated any river inflow to the Aral Sea and caused it to disappear almost completely.

Map showing the location of the Aral Sea in Central Asia.  Source: World Atlas https://www.worldatlas.com/seas/aral-sea.html

In 1960 Aral Sea was the fourth largest inland water body; only the Caspian Sea, Lake Superior, and Lake Victoria were larger. Since then, it has progressively shrunk due to evaporation and lack of recharge by rivers. Before 1965 the Aral Sea received 20–60 km of fresh water per year from rivers and by the early 1980s it received none. By 2007 the Aral Sea shrank to about 10% of its original size and its salinity increased from about 1% dissolved salt to about 10% dissolved salt, which is 3 times more saline than seawater. These changes caused an enormous environmental impact. A once thriving fishing industry is dead as are the 24 species of fish that used to live there; the fish could not adapt to the more saline waters. The current shoreline is tens of kilometers from former fishing towns and commercial ports. Large fishing boats lie in the dried up lakebed of dust and salt ( see abandoned boats above). The primary cause was the diversion of water from the two rivers that supplied the Aral Sea. Furthermore, contributing to the demise of the Aral Sea was the  poorly construction of irrigation canals. Large amount of water were lost through leakage, evaporation and seepage into surrounding soils. Because of this, enormous quantities of freshwater never reached crops or the Aral Sea.

The wetlands of the two river deltas and their associated ecosystems have disappeared. The regional climate is drier and has greater temperature extremes due to the absence of moisture and moderating influence from the lake. In 2003 some lake restoration work began on the northern part of the Aral Sea and it provided some relief by raising water levels and reducing salinity somewhat. The southern part of the Aral Sea has seen no relief and remains nearly completely dry. The destruction of the Aral Sea is one of the planet’s biggest environmental disasters and it is caused entirely by humans. Lake Chad in Africa is another example of a massive lake that has nearly disappeared for the same reasons as the Aral Sea. Aral Sea and Lake Chad are the most extreme examples of large lakes destroyed by unsustainable diversions of river water. Other lakes that have shrunk significantly due to human diversions of water include the Dead Sea in the Middle East, Lake Machar in Pakistan, and Owens Lake and Mono Lake, both in California.

Examples of the Environmental Consequences:

1. Loss of Fish population
2. More than 20 native fish species disappeared
3. Bird populations declined
4. Wetland dried up

Because of this catastrophic event, summers became hotter. Winters became colder, growing seasons became shorter and agriculture productivity came to a stop. We must also look at what this did to the economics of the area. Thousands of people lost there jobs and had to relocate. Communities that depended on fishing experienced unemployment, poverty, and population decline. Although much of the Aral Sea has been permanently altered, some restoration efforts have shown success. In 2005, Kazakhstan completed the Kok-Aral Dam, which separates the North Aral Sea from the more severely depleted southern basin. The construction of the Dam has helped by raising water levels, reduce salinity, improve fish population and has restored some portions of the commercial fishing. The southern portion of the Aral Sea, however, continues to face severe environmental challenges.

The Aral Sea demonstrates how unsustainable water management can permanently alter ecosystems. Rivers must retain enough flow to support downstream ecosystems .Irrigation systems should maximize water-use efficiency. Crops should be matched to local climate conditions. Long-term environmental impacts should be considered before large engineering projects begin. Sustainable water management requires balancing economic development with ecosystem protection.

Water Pollution: 

Water pollution is the contamination of water sources by substances which make the water unusable for drinking, cooking, cleaning, swimming, and other activities. Pollutants include chemicals, trash, bacteria, and parasites. All forms of pollution eventually make their way to water. Air pollution settles onto lakes and oceans. Land pollution can seep into an underground stream, then to a river, and finally to the ocean. Thus, waste dumped in a vacant lot can eventually pollute a water supply.

Water pollutants may cause disease or act as poisons. Bacteria and parasites in poorly treated sewage may enter drinking water supplies and cause digestive problems such as cholera and diarrhea. Hazardous chemicals, pesticides, and herbicides from industries, farms, homes and golf courses can cause acute toxicity and immediate death, or chronic toxicity that can lead to neurological problems or cancers. Many water pollutants enter our bodies when we use water for drinking and food preparation. The pollutants enter the digestive tract. From there, they can reach other organs in the body and cause various illnesses. Chemicals come in contact with the skin from washing clothes, or from swimming in polluted water and may lead to skin irritations. Hazardous chemicals in water systems can also affect the animals and plants which live there. Sometimes these organisms will survive with the chemicals in their systems, only to be eaten by humans who may then become mildly ill or develop stronger toxic symptoms. The animals and plants themselves may die or not reproduce properly.

Nonpoint Source Pollution (NPS)

NPS pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage or hydrologic modification. NPS pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters and ground waters.

• Excess fertilizers, herbicides and insecticides from agricultural lands and residential areas
• Oil, grease and toxic chemicals from urban runoff and energy production
• Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks
• Salt from irrigation practices and acid drainage from abandoned mines
• Bacteria and nutrients from livestock, pet wastes and faulty septic systems
• Atmospheric deposition and hydromodification

States report that nonpoint source pollution is the leading remaining cause of water quality problems. The effects of nonpoint source pollutants on specific waters vary and may not always be fully assessed. However, we know that these pollutants have harmful effects on drinking water supplies, recreation, fisheries and wildlife.

Nonpoint Sources vs. Point Sources

The term "nonpoint source" is defined to mean any source of water pollution that does not meet the legal definition of "point source" in section 502(14) of the Clean Water Act: Summary of the Clean Water Act https://www.epa.gov/laws-regulations/summary-clean-water-act

The term "point source" means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged. This term does not include agricultural storm water discharges and return flows from irrigated agriculture.

 

Large farms that raise livestock are often referred to as concentrated feeding operations (CFOs). These farms are considered potential point sources of pollution because untreated animal waste may enter nearby waterbodies as untreated sewage. Source: NOAA  https://oceanservice.noaa.gov/education/tutorial_pollution/03pointsource.html#:~:text=The%20U.S.%20Environmental%20Protection%20Agency%20(EPA)%20defines%20point%20source%20pollution,common%20types%20of%20point%20sources

When it rains excessively, a combined sewer system may not be able handle the volume of water, and some of the combined runoff and raw sewage will overflow from the system, discharging directly into the nearest waterbody without being treated. This combined sewer overflow (CSO) is considered point source pollution, and can cause severe damage to human health and the environment.

These images show the difference between a combined sewer overflow system found in many older cities, and a sewer system where sanitary and stormwater are completely separated. During heavy rains combined sewer overflow systems mix raw sewage with rainwater runoff and discharge it directly into the nearest waterbody without treatment. Photo: Washington DC Water and Sewer Authority.

Unregulated discharges from point sources can result in water pollution and unsafe drinking water, and can restrict activities like fishing and swimming. Some of the chemicals discharged by point sources are harmless, but others are toxic to people and wildlife. Whether a discharged chemical is harmful to the aquatic environment depends on a number of factors, including the type of chemical, its concentration, the timing of its release, weather conditions, and the organisms living in the area.

To control point source discharges, the Clean Water Act established the National Pollutant Discharge Elimination System (NPDES). Under the NPDES program, factories, sewage treatment plants, and other point sources must obtain a permit from the state and EPA before they can discharge their waste or effluents into any body of water. Prior to discharge, the point source must use the latest technologies available to treat its effluents and reduce the level of pollutants. If necessary, a second, more stringent set of controls can be placed on a point source to protect a specific waterbody.

The National Environmental Policy Act (NEPA) was signed into law on January 1, 1970. NEPA requires federal agencies to assess the environmental effects of their proposed actions prior to making decisions. The range of actions covered by NEPA is broad and includes:

• making decisions on permit applications,
• adopting federal land management actions, and
• constructing highways and other publicly-owned facilities.

Using the NEPA process, agencies evaluate the environmental and related social and economic effects of their proposed actions. Agencies also provide opportunities for public review and comment on those evaluations.

The National Environmental Policy Act (NEPA) was one of the first laws ever written that establishes the broad national framework for protecting our environment. NEPA's basic policy is to assure that all branches of government give proper consideration to the environment prior to undertaking any major federal action that significantly affects the environment.

NEPA requirements are invoked when airports, buildings, military complexes, highways, parkland purchases, and other federal activities are proposed. Environmental Assessments (EAs) and Environmental Impact Statements (EISs), which are assessments of the likelihood of impacts from alternative courses of action, are required from all Federal agencies and are the most visible NEPA requirements. Source:  EPA https://www.epa.gov/nepa/what-national-environmental-policy-act

The Clean Water Act: The Clean Water Act (CWA) establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. The basis of the CWA was enacted in 1948 and was called the Federal Water Pollution Control Act, but the Act was significantly reorganized and expanded in 1972. "Clean Water Act" became the Act's common name with amendments in 1972. Under the Clean Water Act, EPA has implemented pollution control programs such as setting wastewater standards for industry. Furthermore, the EPA has also developed national water quality criteria recommendations for pollutants in surface waters.

Drinking Water:

According to the World Health Organization safe and readily available water is important for public health, whether it is used for drinking, domestic use, food production or recreational purposes. Improved water supply and sanitation, and better management of water resources, can boost countries’ economic growth and can contribute greatly to poverty reduction.

In 2010, the UN General Assembly explicitly recognized the human right to water and sanitation. Everyone has the right to sufficient, continuous, safe, acceptable, physically accessible and affordable water for personal and domestic use.

Sustainable Development Goal target 6.1 calls for universal and equitable access to safe and affordable drinking water. The target is tracked with the indicator of “safely managed drinking water services” – drinking water from an improved water source that is located on premises, available when needed, and free from fecal and priority chemical contamination.

In 2020, 5.8 billion people used safely managed drinking-water services – that is, they used improved water sources located on premises, available when needed, and free from contamination. The remaining 2 billion people without safely managed services in 2020 included:

• 1.2 billion people with basic services, meaning an improved water source located within a round trip of 30 minutes;
• 282 million people with limited services, or an improved water source requiring more than 30 minutes to collect water;
• 368 million people taking water from unprotected wells and springs; and
• 122 million people collecting untreated surface water from lakes, ponds, rivers and streams.

Contaminated water and poor sanitation are linked to transmission of diseases such as cholera, diarrhoea, dysentery, hepatitis A, typhoid and polio. Absent, inadequate, or inappropriately managed water and sanitation services expose individuals to preventable health risks. This is particularly the case in health care facilities where both patients and staff are placed at additional risk of infection and disease when water, sanitation and hygiene services are lacking. Globally, 15% of patients develop an infection during a hospital stay, with the proportion much greater in low-income countries.

Inadequate management of urban, industrial and agricultural wastewater means the drinking-water of hundreds of millions of people is dangerously contaminated or chemically polluted. Natural presence of chemicals, particularly in groundwater, can also be of health significance, including arsenic and fluoride, while other chemicals, such as lead, may be elevated in drinking-water as a result of leaching from water supply components in contact with drinking-water.

Some 829 000 people are estimated to die each year from diarrhoea as a result of unsafe drinking-water, sanitation and hand hygiene. Yet diarrhoea is largely preventable, and the deaths of 297 000 children aged under 5 years could be avoided each year if these risk factors were addressed. Where water is not readily available, people may decide handwashing is not a priority, thereby adding to the likelihood of diarrhoea and other diseases.

Diarrhoea is the most widely known disease linked to contaminated food and water but there are other hazards. In 2017, over 220 million people required preventative treatment for schistosomiasis – an acute and chronic disease caused by parasitic worms contracted through exposure to infested water.

In many parts of the world, insects that live or breed in water carry and transmit diseases such as dengue fever. Some of these insects, known as vectors, breed in clean, rather than dirty water, and household drinking water containers can serve as breeding grounds. The simple intervention of covering water storage containers can reduce vector breeding and may also reduce fecal contamination of water at the household level ( WHO https://www.who.int/news-room/fact-sheets/detail/drinking-water )

In October of 2022 was the 50th anniversary of the Clean Water Act, which was passed by Congress on October 18, 1972—establishing a nationwide approach to improving the quality of our nation’s lakes, rivers, streams, and other water bodies. Over the last 50 years, the health of our waters has improved, but threats to water safety remain.

The CWA requires the Environmental Protection Agency (EPA)—along with states, tribes, and territories—to monitor the quality of U.S. lakes, rivers, streams, estuaries, and other water bodies. EPA and states are also required to list water bodies that are impaired by pollutants and to plan for cleaning them up. Yet, EPA’s most recent report (from 2017) says that only about half of U.S. waters have been assessed to date, meaning that quality of the other half has not been assessed and their status is unknown.

Ensuring safe drinking water

Under the Safe Drinking Water Act (SDWA), EPA establishes legally enforceable standards that limit the levels of specific contaminants in drinking water. EPA identifies unregulated contaminants, monitors them, and determines whether to regulate them based on things like how dangerous they are to public health, and how often they occur. The agency has issued standards for around 90 contaminants to date.

However, EPA could more efficiently collect data on unregulated contaminants in order to determine whether they need to be regulated. Additionally, public water systems must comply with monitoring, reporting, and other requirements established by EPA and responsible states. But the data that states reported to EPA did not always reflect the frequency of health-based and monitoring violations by community water systems or the status of enforcement actions.

Most Recent Map of Impaired Waters (As of 2015)

Contaminated water:  Both the Clean Water Act and the Safe Drinking Water Act defines the term "contaminant" as meaning any physical, chemical, biological, or radiological substance or matter in water. Therefore, the law defines "contaminant" very broadly as being anything other than water molecules. Drinking water may reasonably be expected to contain at least small amounts of some contaminants. Some drinking water contaminants may be harmful if consumed at certain levels in drinking water while others may be harmless. The presence of contaminants does not necessarily indicate that the water poses a health risk.

Limited monitoring makes it difficult to detect and warn of harmful substances in water bodies. For example, we recently reported that limited monitoring for harmful algal blooms (HABs) in fresh water, may hamper efforts to identify the risks blooms could pose to human health and aquatic life. Harmful algal blooms, or HABs, occur when colonies of algae — simple plants that live in the sea and freshwater — grow out of control and produce toxic or harmful effects on people, fish, shellfish, marine mammals and birds. The human illnesses caused by HABs, though rare, can be debilitating or even fatal. All 50 states have experienced harmful algal blooms and, according to federal agencies, may experience more blooms in the future with climate change and warming waters.

Imagery of the Western Lake Erie harmful algal bloom from September 26, 2017. The scum shown here near downtown Toledo stretched all the way to Lake Ontario. This photo is from Landsat-8 (a NASA/USGS satellite Source: https://oceanservice.noaa.gov/facts/hab-solutions.html

Since 2015, the Environmental Protection Agency (EPA) has modified one of its three national initiatives emphasizing compliance with the Clean Water Act and has discontinued two others (see fig below). The goal of the modified initiative is to reduce significant noncompliance with National Pollutant Discharge Elimination System (NPDES) permits by half by the end of fiscal year 2022. Such permits set limits on discharges of wastewater from point sources, such as a pipe from an industrial facility. This goal supports EPA's strategic objective to increase compliance with environmental laws in its strategic plan for fiscal years 2018-2022. EPA discontinued its initiatives focused on animal waste pollution and raw sewage and stormwater runoff, returning these areas to the core enforcement program in 2018 and 2019, respectively. As a result, these areas no longer receive the heightened attention and focused resources of the national initiatives, but the agency still pursues enforcement actions when needed.

Changes in EPA's Clean Water Act National Initiatives(Source: https://www.gao.gov/products/gao-21-290)

One key program under the CWA established requirements for regulating and limiting point sources of pollution—pollution that is discharged into waters from sources such as pipes from industrial facilities and wastewater treatment plants.

This type of pollution is allowed, but requires permits. Permit holders must self-report discharges and noncompliance with water quality requirements. In 2021, the U.S. Government Accountability Office (GAO) found that EPA lacks reliable information needed to ensure polluters are complying with their permits. We also recommended steps to improve that will help EPA identify and reduce illegal discharges.

While point source pollution is an important issue, the leading cause of water pollution is nonpoint sources. These sources come from runoff that carries sediment, oil, bacteria, toxins, and other pollutants from farms, yards, and paved areas (e.g., streets and parking lots) into nearby waters. Such pollution can harm fish and other aquatic life, lead to the development of harmful algal blooms, and contribute to ocean acidification in coastal waters, an emerging threat to marine life on which was previously by the GAO.

The graphic above shows examples of how pollutants from both point sources and nonpoint sources enter our waters

Recently, the discovery of widespread pollution of rivers, lakes, and groundwater by persistent chemicals called PFAS, has raised concerns about the risks to human health. PFAS are commonly used in consumer goods, such as nonstick pans, food packaging, and carpeting. They are considered “forever” chemicals because they don’t break down in the environment and can accumulate in our bodies. In 2021, the GAO reported on EPA’s attention to PFAS, including its efforts to identify and control industrial sources of them. In April 2022, EPA announced actions to protect communities and the environment from PFAS. These measures include using the Act’s permitting authorities to reduce PFAS discharges, obtaining monitoring information on PFAS sources and quantities, and using the data for EPA decisions about restricting releases of PFAS by industrial facilities and others.

At least 45% of the nation’s tap water is estimated to have one or more types of the chemicals known as per- and polyfluorinated alkyl substances, or PFAS, according to a new study by the U.S. Geological Survey. There are more than 12,000 types of PFAS, not all of which can be detected with current tests; the USGS study tested for the presence of 32 types.

PFAS are a group of synthetic chemicals used in a wide variety of common applications, from the linings of fast-food boxes and non-stick cookware to fire-fighting foams and other purposes. High concentrations of some PFAS may lead to adverse health risks in people, according to the U.S. Environmental Protection Agency. Research is still ongoing to better understand the potential health effects of PFAS exposure over long periods of time. Because they break down very slowly, PFAS are commonly called “forever chemicals.” Their persistence in the environment and prevalence across the country make them a unique water-quality concern.

The study tested for 32 individual PFAS compounds using a method developed by the USGS National Water Quality Laboratory. The most frequently detected compounds in this study were PFBS, PFHxS and PFOA. The interim health advisories released by the EPA in 2022 for PFOS and PFOA were exceeded in every sample in which they were detected in this study.

Before the passage of the Clean Water Act, large numbers of our nation’s lakes, rivers, and streams, were polluted with raw sewage, industrial chemicals, and dangerous metals. For example, in Washington, D.C., the Potomac River was so polluted with sewage that the smell across parts of the National Mall was nearly unbearable. The Cuyahoga River in Ohio was so polluted with oil and debris that it used to catch on fire!

Original Caption: Firemen stand on a bridge over the Cuyahoga River to spray water on the tug Arizona, as a fire, started in an oil slick on the river, sweeps the docks at the Great Lakes Towing Company site in Cleveland Nov., 1st. The blaze destroyed three tugs, three buildings, and the ship repair yards. Bettmann / Contributor via Getty Images (https://www.smithsonianmag.com/history/cuyahoga-river-caught-fire-least-dozen-times-no-one-cared-until-1969-180972444/) 

While the sources of pollution that created such situations have largely been addressed, threats from more dispersed sources—such as stormwater runoff that carries pollutants into our waters—will require further actions. Emerging threats resulting from a changing climate also need to be addressed. The key to tackling these threats will require using the tools provided by the Clean Water Act. But more action may be needed to strengthen the Act and help it meet the goals established half a century ago.

Lead in Drinking Water U.S. Government Accountability Office (GAO) https://www.gao.gov/water-quality-and-protection

How Oil and Gas Wells Can Contaminate Underground Drinking Water. Source: https://www.gao.gov/water-quality-and-protection

Source: U.S. Government Accountability Office https://www.gao.gov/blog/2018/03/22/bottoms-up-to-clean-drinking-water

Although the rule requires water systems to test in high-risk homes and buildings with lead pipes, the locations of many lead pipes are unknown.

Children attending K-12 public schools may also be at risk of lead exposure from drinking water. Lead in school drinking water is a concern because it is a daily source of water for more than 50 million children enrolled in public schools. Similar to child care centers, the pattern of schools’ schedules—including time off during weekends, holidays, and extended breaks—can contribute to standing water in the schools’ plumbing systems, possibly allowing lead to leach into the water.

The GAO found that an estimated 41% of school districts—serving 12 million students—had not tested school water for lead in 2016 or 2017. Similarly, another 16% of school districts didn’t know whether they had tested for lead at all. Of the school districts that did test for lead (43% of those we surveyed—representing some 35 million students), about 37% found elevated lead levels in their water. The figure below shows the estimated percent of school districts testing and those that found elevated lead levels.

There are no federal laws requiring lead testing of drinking water in schools that receive water from public water systems, even though these systems are regulated by the EPA. According to the EPA, at least 8 states had requirements for schools to test for lead in water, and an additional 13 states supported school districts’ voluntary efforts with funding or in-kind support for tests and remediation.

As of the GAO report in 2018, the EPA has taken a variety of actions, such as communicating the importance of testing for lead in school drinking water and collaborating with the Department of Education. In 2019 and 2020, EPA awarded grants authorized by the Water Infrastructure Improvements for the Nation Act to states and the District of Columbia to help with voluntary testing in schools and child care facilities (Source; https://www.gao.gov/blog/protecting-children-lead-exposure-schools-and-child-care-facilities)

Water is the only substance that occurs naturally on Earth in three forms: solid, liquid and gas. Shallow groundwater is the largest reservoirs of fresh water however, it is not easily located. Although rivers and lakes are the most heavily used water resources, they represent only a tiny amount of the world’s water. The water cycle shows the movement of water through different reservoirs, which include oceans, atmosphere, glaciers, groundwater, lakes, rivers, and biosphere. Solar energy and gravity drive the motion of water in the water cycle. Precipitation is a major control of fresh water availability, and it is unevenly distributed around the globe. Flowing water from rain and melted snow on land enters river channels by surface runoff and groundwater seepage.

Lakes can also be an excellent source of fresh water for human use. They usually receive water from surface runoff and groundwater discharge. The Great Lakes hold 21% of the world's surface fresh water. Although glaciers represent the largest reservoir of fresh water, they generally are not used as a water source because they are located too far from most people. If Earth’s climate continues to warm, the melting glaciers will cause an additional rise in sea level.

An Earth material that is capable of supplying groundwater from a well at a useful rate—i.e., it has relatively high permeability and medium to high porosity—is called an aquifer. A spring is a water resource formed when the side of a hill, a valley bottom or other excavation intersects groundwater at or below the local water table, below which the subsurface material is saturated with water. Groundwater and surface water (rivers, lakes, swamps, and reservoirs) are strongly interrelated because both are part of the same overall resource. Major groundwater removal (from pumping or drought) can lower the levels of surface water and vice versa. People need water to produce the food, energy, and mineral resources they use—commonly large amounts of it.

The water demand of an area is a function of the population and other uses of water. The water crisis refers to a global situation where people in many areas lack access to sufficient water or clean water or both. More than 2.2 billion people globally lack access to safely managed drinking water (United Nations, 2019), while millions of people in the United States are without clean, reliable water, lack basic plumbing, or rely on water systems with Safe Drinking Water Act violations. Today, the Human Right to Water is formally recognized by the United Nations, the State of California, and dozens of global businesses. Yet, the United States as a whole has yet to recognize the Human Right to Water or meet the United Nations Sustainable Development Goals for clean water and sanitation (SDG 6), climate action (SDG 13), or reduced inequalities (SDG 10)

Water pollution is the contamination of water sources by substances which make the water unusable for drinking, cooking, cleaning, swimming, and other activities. Pollutants include chemicals, trash, bacteria, and parasites. Non-point pollution (NPS) generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage or hydrologic modification. The term "point source" means any discernible, confined and discrete conveyance. When it rains excessively, a combined sewer system may not be able handle the volume of water, and some of the combined runoff and raw sewage will overflow from the system, discharging directly into the nearest waterbody without being treated. Under the Safe Drinking Water Act (SDWA), EPA establishes legally enforceable standards that limit the levels of specific contaminants in drinking water. At least 45% of the nation’s tap water is estimated to have one or more types of the chemicals known as per- and polyfluorinated alkyl substances, or PFAS. Before the passage of the Clean Water Act, large numbers of our nation’s lakes, rivers, and streams, were polluted with raw sewage, industrial chemicals, and dangerous metals.

References:

Basic Information about Nonpoint Source (NPS) Pollution

Information on Non-Point Pollution

Monitoring Unregulated Contaminants in Drinking Water

Unregulated Contaminants in Drinking Water

Overview of Total Maximum Daily Loads (TMDLs)

Total Maximum Daily Loads

Explore Search: Common Water Issues

Common Water Issues

Tap Water study detects PFAS across US

Tap Water Study on PFAS

Our Current Understanding of the Human Health and Environmental Risks of PFAS

Gauging Progress on the Clean Water Act

50 Years after the Clean Water Act

NASA TERRA Why Citizen Science for Water Quality?

Water Quality Cirtizen Science for Water Quality

Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York).

NASA Earth Observatory NASA Earth Observatory Total Rain Fall

Michigan State University Great Lakes Watershed

Page Contact Information: USGS Publishing Network Last modified: Friday, January 11 2013, 12:27:14 PM

Water Availability and Use Science Program

By: Cheryl A. Dieter, Molly A. Maupin, Rodney R. Caldwell, Melissa A. Harris, Tamara I. Ivahnenko, John K. Lovelace, Nancy L. Barber, and Kristin S. Linsey

Estimate Water Usage USGS 2015

National Oceanic Atmospheric Administration (NOAA)  Point Sourse Pollution

Changes in EPA's Clean Water Act National Initiatives Changes to the Clean Water Act

Types of Drinking Water Contaminants https://www.epa.gov/ccl/types-drinking-water-contaminants

Lead in Drinking Water U.S. Government Accountability Office (GAO) Lead in Drinking Water

U.S. Government Accountability Office Bottom's Up to Clean Drinking Water

Data Centers and water use:

From Energy Use to Air Quality, the Many Ways Data Centers Affect US Communities ,Carla D. Walker and Ian Goldsmith February 17, 2026 World Resources Institute

Data Centers and Water Consumption, Miguel Yañez-Barnuevo, June 25,2025,Environmental and Energy Study Institute

https://www.eesi.org/articles/view/data-centers-and-water-consumption

Understanding How Data Centers Impact Surface and Ground Waters, University of Georgia College of Agricultural & Environmental Science, https://fieldreport.caes.uga.edu/publications/TP121/how-data-centers-impact-surface-and-ground-waters/

VOICES: Unlikely opportunities for water progress in raging data center debate, Mike Shriberg | Planet Detroit | April 21, 2026

Retrieved from University of Michigan School for Environment and Sustainability https://seas.umich.edu/news/voices-unlikely-opportunities-water-progress-raging-data-center-debate

Nuoa Lei, Jun Lu, Arman Shehabi, Eric Masanet, The water use of data center workloads: A review and assessment of key determinants,
Resources, Conservation and Recycling, Volume 219, 2025, 108310, ISSN 0921-3449, https://doi.org/10.1016/j.resconrec.2025.108310.
(https://www.sciencedirect.com/science/article/pii/S0921344925001892)