ENVSCI - Water and Water Pollution

hydrologic cycle

collects, purifies, recycles, and distributes the world’s freshwater supply

surface runoff

Water that flows across the Earth and empties into rivers, streams, lakes, etc., and so does not infiltrate the ground or evaporate into the atmosphere

watershed or drainage basin

region from which surface water drains into a body of water

reliable runoff

is the runoff that is stable from one year to the next and can be counted on for a water supply

groundwater

Water that percolates down through the ground and is stored in pores, crevices

aeration zone

close to the surface and pores/spaces here contain a mixture of air and water

saturation zone

the spaces in the ground are filled with water

water table

located at the top of the zone of saturation

aquifers

is deeper down in the geologic layers and is like an elongated sponge with watertight layers of rock or clay below the aquifer to keep water from seeping out

natural recharge

replenishes an aquifer through the precipitation that percolates down through soil and rock

Lateral recharge

replenished from the side of nearby streams

Water mining

withdraws water from deep, underground, ancient deposits of water that are not generally recharged

Consumptive water

water not available for reuse due to evaporation, seepage into soil contamination, or movement to another area

Water scarcity

arises from a dry climate, drought, dry soil, and too many people straining the water supply

hydrological poverty

people have no access or cannot afford clean water at a reasonable cost

Dams and reservoirs

capture and store runoff water; used to control floods, generate electricity, and to irrigate

Desalination

removes salt from ocean or brackish groundwaters

distillation

heats saltwater until it evaporates and condenses as fresh water; the salts are left behind as solids

reverse osmosis

a method of pumping saltwater under high pressure through a thin membrane

Lifeline water pricing

a means of giving each household an amount of water for basic needs; excess usage means higher prices

center-pivot low-pressure sprinkler irrigation

sprays water directly on a crop rather than flood irrigation, which provides water flowing in ditches in crop fields.

Low-energy precision application (LEPA)

sprinklers spray water closer to the ground than the center-pivot low-pressure sprinkler, using less energy and less water

gravity flow irrigation

send water down irrigation ditches in pulses, rather than in a continuous stream

soil moisture detectors

used to water crops only when they need it

Drip irrigation

are the most efficient ways to move small amounts of water to crops.

pedal-powered treadle pumps

Poor farmers use this to move water into irrigation ditches and buckets/tanks with holes for irrigation.

xeriscaping

replacing green lawns and ornamental shrubbery with vegetation that needs little water

flooding

occurs when heavy rain and snowmelt cause streams to overflow onto adjacent land, a floodplain

floodplain

contain fertile soil, ample water, nearby rivers for transportation and recreation, flat land for crops, buildings, highways, and railroads.

Great floods

used to occur about every 50 years or so, but since the 1970s they now occur about every 4 years

Channelization

reduces upstream flooding but increases stream velocity and removes bank vegetation

Levees

can be built along the sides of streams. This method contains/accelerates the stream flow, increasing the possibility for damage downstream.

water pollution

any chemical, biological, or physical change in water quality that has a harmful effect on living organisms

Point sources

discharge pollutants at specific locations through drainpipes, ditches, or sewer lines into bodies of surface water.

Nonpoint sources

are scattered and diffuse and can’t be traced to any single site of discharge.

eutrophication

Natural nutrient enrichment of lakes from runoff

Natural eutrophication

eutrophication that can enrich the abundance of desirable organisms

cultural eutrophication

eutrophication that occurs near urban or agricultural areas and can lead to serious pollution problems.

Clean Water Act

sets standards for allowed levels of key water pollutants and requires polluters to obtain permits that specify the amounts of pollutants they can discharge into aquatic systems.

septic tanks

_ and various levels of sewage treatment can reduce point-source water pollution

Primary sewage treatment

is a physical process that removes grit, floating objects, and suspended solids. A settling tank allows suspended solids to settle out as sludge.

Secondary sewage treatment

a biological process where aerobic bacteria remove up to 90% of dissolved and biodegradable, oxygen-demanding organic wastes.

Tertiary sewage treatment

Here a combination of chemical and physical processes remove specific pollutants left by the other methods.

bleaching

removes colors and disinfects water to kill disease-causing bacteria and some viruses

chlorination

usual method of water disinfection