Although Earth has plenty of water, about (a)     percent of it is salty and not consumable by most terrestrial organisms

The (a)   (UNDP) predicts that by 2025, up to two-thirds of the human population will live in areas subject to water-stressed conditions.

(a)   is composed of molecules of H2O, each consisting of two atoms of hydrogen and one atom of oxygen.

Water molecules are (a)   —that is, one end of the molecule has a positive electrical charge, and the other end has a negative charge

The negative (oxygen) end of one water molecule is attracted to the positive (hydrogen) end of another water molecule, forming a (a)   between the two molecules.

Hydrogen bonds are the basis for many of water’s physical properties, including its high melting/ freezing point (0°C, 32°F) and high boiling point (100°C, 212°F).

(a)  

Water is a (a)   , meaning that it can dissolve many materials

water is never completely pure because it contains dissolved gases from the atmosphere and dissolved mineral salts from the land. T or F?

(a)  

In the (a)   , water continuously circulates through the environment, from the ocean to the atmosphere to the land and back to the ocean

The result is a balance of the water resources in the ocean, on the land, and in the atmosphere. The hydrologic cycle provides a continual renewal of the supply of fresh water on land, which is essential to terrestrial organisms.

(a)  

is water found in streams, rivers, lakes, ponds, reservoirs, and wetlands.

(a)  

(areas of land covered with water for at least part of the year)

(a)  

Precipitation that remains on the surface of the land and does not seep down through the soil

(a)  

The movement of fresh water from precipitation and snowmelt to rivers, lakes, wetlands, and the ocean.

(a)  

The runoff of precipitation from the land replenishes surface waters and is considered a renewable, although finite, resource.

(a)  

A _____, or _______, is the area of land drained by a single river or stream

(a)  

The supply of fresh water under Earth’s surface that is stored in underground aquifers.

(a)  

Groundwater flows through permeable sediments or rocks slowly, typically covering distances of several millimeters to a few meters per day. This process of downward movement and accumulation is called (a)   .

are underground reservoirs in which groundwater is stored

(a)  

Unconfined aquifers are recharged by surface water directly above them; the quantity of groundwater stored in an unconfined aquifer thus depends on the amount of precipitation in that area.

(a)  

Most groundwater is considered a nonrenewable resource because it has taken hundreds or even thousands of years to accumulate, and usually only a small portion of it is replaced each year by seepage of surface water. T or F?

(a)  

______, or ______, are fragile ecosystems in which plant growth is limited by lack of precipitation.

(a)  

(a)   receive more precipitation than deserts but are subject to frequent and prolonged droughts.

(a)   from excessive removal of groundwater lowers the water table, the upper surface of the saturated zone of groundwater

the upper surface of the saturated zone of groundwater

(a)  

The removal of groundwater faster than it can be recharged by precipitation or melting snow.

(a)  

Prolonged aquifer depletion drains an aquifer dry, effectively eliminating it as a water resource.

(a)  

aquifer depletion from porous sediments causes (a)   , or sinking, of the land above it

Saltwater intrusion occurs along coastal areas when groundwater is depleted faster than it recharges. Saltwater intrusion is also occurring in lowlying areas due to sea-level rise associated with global climate change

(a)  

Saltwater intrusion is also occurring in low-lying areas due to sea-level rise associated with global climate change.

(a)  

The movement of seawater into a freshwater aquifer near the coast.

(a)  

(a)   , the largest groundwater deposit in the world, composed primarily of the Ogallala Aquifer

(a)   , where rivers empty into seawater, become saltier when surface waters are overdrawn, which reduces their productivity

_____ and _____, which serve as breeding grounds for many species of birds and other animals, also play a vital role in the hydrologic cycle

(a)  

One of the most serious water supply problems in the United States is in the (a)  

The river’s headwaters are formed from snowmelt in Colorado, Utah, and Wyoming, and major tributaries—collectively called the upper Colorado

(a)  

The lower Colorado River runs through part of Arizona and then along the border between Arizona and both Nevada and California before crossing into Mexico and emptying into the Gulf of California.

(a)  

salt to accumulate in the soil

(a)  

The gradual accumulation of salt in soil, often as a result of improper irrigation methods.

(a)  

In a 2013 World Resources Institute assessment, a nation’s water supply is considered stressed if the ratio of water withdrawals to total water supply is high, meaning that water may be scarce for communities, farms, and industries. Thirty-six countries face “extremely high” levels of water stress.

(a)  

____ and ____ are but two of many examples of water stress around the world.

(a)  

Three-fourths of the world’s 200 or so major watersheds are shared between at least two nations.

(a)  

(a)   means careful human use of water resources so that water is available for future generations and for existing nonhuman needs

Water supplies are obtained by building dams, diverting water, or removing salt from seawater or salty groundwater, through a process called (a)   .

(a)   , which includes reusing water, recycling water, and improving water-use efficiency, augments water supplies and is an important aspect of sustainable water use.

Economic policies are also important in managing water sustainably: When water is inexpensive, it tends to be wasted. Raising the price of water to reflect the actual cost generally promotes its more efficient use.

(a)  

The wise use of water resources, without harming the essential functioning of the hydrologic cycle or the ecosystems on which present and future humans depend.

(a)  

Dams generate electricity and ensure a year-round supply of water in areas with seasonal precipitation or snowmelt, often for populations that have outgrown other water sources, but many people think their costs outweigh their benefits

(a)  

The (a)   , the fourth-largest river in North America,

_______, also called ____ or trickle irrigatio_______, in which pipes with tiny holes bored in them convey water directly to individual plants

(a)  

Microirrigation substantially reduces the water needed to irrigate crops—usually by 40 percent to 60 percent compared to traditional irrigation—and also reduces the amount of salt that irrigation water leaves in the soil. T or F?

(a)  

A type of irrigation that conserves water by piping it to crops through sealed systems.

(a)  

is water that has already been used in sinks, showers, washing machines, and dishwashers.

(a)  

Water pollution is a global problem that varies in magnitude and type of pollutant from one region to another. T or F?

(a)  

A physical, biological, or chemical change in water that adversely affects the health of humans and other organisms.

(a)  

Water pollutants are divided into eight categories: sewage, disease-causing agents, sediment pollution, inorganic plant and algal nutrients, organic compounds, inorganic chemicals, radioactive substances, and thermal pollution.

(a)  

Wastewater from drains or sewers (from toilets, washing machines, and showers); includes human wastes, soaps, and detergents.

(a)  

Sewage and other organic wastes are measured in terms of their __________________ (BOD), or ___________________

(a)  

(a)   (BOD) The amount of oxygen that microorganisms need to decompose biological wastes into carbon dioxide, water, and minerals.

BOD is usually expressed as milligrams of dissolved oxygen per liter of water for a specific number of days at a given temperature.

(a)  

An (a)   lake has cool, clear water and supports small populations of aquatic organisms

is the enrichment of a lake, an estuary, or a slow-flowing stream by inorganic plant and algal nutrients such as phosphorus; an enriched body of water is said to be eutrophic.

(a)  

Some human activities, however, greatly accelerate eutrophication. This fast, human-induced process is usually called (a)  

results from enrichment of aquatic ecosystems by nutrients found predominantly in fertilizer runoff and sewage.

(a)  

Overnourishment of an aquatic ecosystem by nutrients such as nitrates and phosphates due to human activities such as agriculture and discharge from sewage treatment plants.

(a)  

The sources of water pollution are classified into two types: point source pollution and nonpoint source pollution

(a)  

is discharged into the environment through pipes, sewers, or ditches from specific sites such as factories or sewage treatment plants

(a)  

Pollutants that enter bodies of water over large areas rather than at a single point cause _________, also called _________

(a)  

Water pollution that can be traced to a specific point of entry.

(a)  

Pollution that enters bodies of water over large areas rather than being concentrated at a single point of entry.

(a)  

According to the Environmental Protection Agency (EPA), agriculture is the leading source of water quality impairment of surface waters nationwide and is responsible for 72 percent of the water pollution in U.S. rivers.

(a)  

combined sewer systems, in which human and industrial wastes mix with urban runoff from storm sewers before flowing into sewage treatment plants.

(a)  

Even the largest sewage treatment plant can process only a given amount of wastewater each day, so when too much water enters the system—such as after a heavy rainfall or large snowmelt—the excess, known as combined sewer overflow,

(a)  

the EPA proposed in 1994 that water treatment facilities reduce the maximum permissible level of chlorine in drinking water. Alternatives to chlorination include using chloramine

(a)  

a disinfectant that does not form harmful by-products, and filtering water through activated carbon granules, a method requiring less chlorine that is used by the city of Cincinnati

(a)  

removes suspended and floating particles, such as sand and silt, through mechanical processes such as screening and gravitational settling

(a)  

Treatment of wastewater that involves removing suspended and floating particles through mechanical processes

(a)  

The solid material that settles out at this stage is called p rimary sludge

(a)  

uses microorganisms (aerobic bacteria) to decompose the suspended organic material in wastewater

(a)  

Biological treatment of wastewater to decompose suspended organic material; secondary treatment reduces the water’s biochemical oxygen demand.

(a)  

(a)   a slimy mixture of bacteria-laden solids.

(a)   , include a variety of biological, chemical, and physical processes.

Advanced wastewater treatment methods that are sometimes employed after primary and secondary treatments

(a)  

Tertiary treatment reduces phosphorus and nitrogen, the nutrients most commonly associated with enrichment, and purifies wastewater for reuse in communities where water is scarce.

(a)  

Municipal Sewage Treatment: Primary, Secondary, Tertiary Treatment

(a)  

The (a)   , passed in 1974, set uniform federal standards for drinking water, to guarantee safe public water supplies throughout the United States. This law required the EPA to determine the maximum contaminant level, which is the maximum permissible amount of any water pollutant that might adversely affect human health

The (a)   affects the quality of rivers, lakes, aquifers, estuaries, and coastal waters in the United States. Originally passed as the Water Pollution Control Act of 1972, it was amended and renamed the Clean Water Act of 1977; additional amendments were made in 1981 and 1987

The Clean Water Act has two basic goals: to eliminate the discharge of pollutants in U.S. waterways and to attain water quality levels that make these waterways safe. for fishing and swimming.

(a)  

Under the provisions of this Clean Water Act, the EPA is required to set up and monitor national emission limitations, the maximum permissible amounts of water pollutants that can be discharged from a sewage treatment plant, factory, or other point source

(a)