Part 1Water as a Resource

Precipitation around the worldWet: along equator and 60

Dry: 30 and poles

Distribution of Earth’s water97.6% in oceans (saltwater)

2.4% is freshwatermost freshwater is frozen (N and S poles, glaciers)

very little freshwater is directly accessible

Major Water Compartments

Potential fates of precipitationevaporation: back to atmosphere

transpiration: through plants to atmosphereinfiltration: to soil and groundwater

runoff: rare in most natural ecosystems

Humans have increased runoff…

• Runoff takes topsoil with it!!

Rill ErosionRill Erosion(most soil erosion loss)(most soil erosion loss) Gully ErosionGully Erosion

The problem with runoff…

Groundwaterzone of aeration: soil pores filled with water and air,

zone of saturation: soil pores filled with water,groundwater: water in zone of saturation,

water table: top of groundwater…

Aquifersaquifer: porous, water-bearing layer(s) of sand, gravel, and/or rock

recharge zone: area where water enters aquifer

Aquifers in Pennsylvaniawhere does southwest PA get its water?

Aquifers: confined vs. unconfined-springs and artesian

wellsRecharge

zone

Global Water Use

#1. agriculture (mostly irrigation)

#2. industrial

#3. domestic

Global water usewater use in low-, middle-, and high-income nations:

shifts from agriculture toward industry

Irrigation in dry regionswater is a precious resource

Irrigation

Industrial water useused as a solvent, and as a cooling agent

Domestic water useabout 2/3 used in the bathroom (toilet flushing and bathing)

relatively little used for drinking and cooking

Water Supply

• Because water is essential for most human activities, long-term human habitation requires a renewable water supply=Water resources that are replenished regularly

(mainly surface water and shallow ground water)• Often dependant on precipitation

Where do we get our water?well: hole in soil/bedrock from which water is extracted

many cause a cone of depression in water tablemay cause nearby shallow wells to “run dry”

Where do we get our water?reservoirs: created by construction of dams

constructed for:1) flood control

2) consistent water supply

The problems with dams

• Water in reservoirs evaporates more quicklywater loss

• They change natural, seasonal flow regimes

• They stop the water and allow sediment to settle behind the dam– Eventually the reservoir will

fill with sediment

The problems with dams

• They drown valleys and destroy free-flowing rivers

• They impede migrations of fish and land animals

Water Use

• Water can be reused if it is not contaminated• Withdrawal- total water taken from a water body

(most could be returned to circulation)• Consumption- water evaporated, absorbed or

contaminated (water “lost” to immediate future use

• We must use water conscientiously to protect and conserve it!

• Conservative irrigation may save vast amounts of water

Water use and conservationuse of native plants gaining popularity in dry regions,

native plants are well-adapted to dry conditions

Watersheds

• Watershed = the area drained by a particular stream

• Watershed conservation involves the idea of monitoring and conserving the resources within a watershed’s boundaries to protect the water resource

Part 2 Water Pollution

• Any physical, biological, or chemical change in water quality that adversely affects living organisms can be considered pollution.– Point Sources - Discharge pollution from specific

locations (channeled).• Factories, Power plants

– Non-Point Sources - Scattered or diffuse, having no specific location of discharge.

• Agricultural fields, Feedlots• Atmospheric Deposition

Point-source pollutionpoint-source pollution: can be traced to a discrete point

example = pipe from factory

Nonpoint-source pollutionnonpoint-source pollution: pollution comes from broad area

example = erosion, fertilizers from farms

Infectious Agents

• Main source of waterborne pathogens is untreated and improperly treated human waste.– Animal wastes from feedlots and fields is also

an important source of pathogens.

Testing water for infectious agents

• Individual disease-causing organisms are difficult/expensive to test for.

• Infectious agents are more common in water with high concentrations of untreated waste.

• Coliform bacteria (E. coli) are common in the digestive tracts of warm blooded animals.

• Fecal coliforms are used as indicators that other more infectious agents may also be present in water.– If a test shows coliform bacteria are present, there is

untreated waste in the water and it is assumed to be unsafe to drink.

Threats to groundwater:illegal dumping

faulty septic systemsfertilizer & pesticide application

leaky tanks

Movement of pollutantsgroundwater does NOT always move straight down!

Groundwater contaminationmovement depends on density relative to water

Pollution by Organic Material (untreated sewage)

decomposition of OM “uses up” dissolved oxygen in water(high Biological Oxygen Demand = BOD)little or none left for aquatic organisms

Excess nutrientseutrophication: increase in nutrient levels which leads to

excess productivity (algal bloom),(then decomposition of dead algae depletes DO)

Cultural Eutrophication

• Large excesses of nutrients are often put into rivers for “disposal”

• When these rivers empty into the sea/ocean they can cause large “dead zones” without any dissolved Oxygen (DO)

• The largest dead zone in the world is in the Gulf of Mexico at the mouth of the Mississippi– During summer months (when algae growth is

highest) the dead zone may reach 7,000 square miles, the size of NJ.

Wastewater treatment--Septic systemwastewater must percolate--1. fast enough to handle daily load,2. slow enough to allow “purification”,potential drainfield sites are subject to “perc” test

Septic systemssolids settle in septic tank where they are decomposed by bacteria,

if bacteria are killed (chemicals), system starts to fail (YUCK!)if too many “cloggers” go down the drain, system starts to fail (YUCK!)

Wastewater treatment plantsthe idea: centralize treatment to ensure proper treatment

problem: expensive to build and maintainup to three treatment levels

Inorganic Pollutants

• Some inorganic materials are released by natural processes

• Humans accelerate production of many chemicals by mining, processing, and discarding of materials

• Metals- many are toxic at high concentrations, and may bioaccumulate

• Salts- some are toxic (selenium, arsenic). Some accumulate and poison soils and local waters

• Acids and bases- can disrupt the fragile balance of life in surface waters. Acids may also dissolve other toxic substances like metals.

Organic Chemicals

• Thousands of natural and synthetic organic chemicals are used to make pesticides, plastics, pharmaceuticals, pigments, etc.

• Two most important sources of toxic organic chemicals in water are:– Improper disposal of industrial and household

wastes.– Runoff of pesticides from high-use areas.

• Fields, roadsides, golf courses

Sediment

• Although natural, sediment can cause major environmental problems.– Fill lakes/reservoirs, navigation channels in Rivers– Make it hard to treat water for drinking– Smother stream bottom (benthic) habitatkill bugs

and fish eggs. May choke out fish (clogged gills)– Blocks sunlightreduces primary production in

aquatic systemsmay reduce overall biomass of any system linked to the affected aquatic ecosystem

• Anthropogenic erosion is the largest water largest water pollution problem in the USApollution problem in the USA.

Thermal Pollution

• Increases/decreases in water temperature can affect water quality and aquatic life.

• Water in nature changes temp slowly. Organisms are not adapted to change temp quickly.

• Vegetation and runoff patterns can affect water temps.

WATER QUALITY TODAY• Areas of Progress

– Clean Water ActClean Water Act (1972) established a National Pollution Discharge Elimination System (NPDES) which requires a permit for any entity dumping wastes in surface waters.

• In 1999, EPA reported 91.4% of all monitored river miles and 87.5% of all accessed lake acres are suitable for their designated uses.*

– Most progress due to municipal sewage treatment facilities.

– Safe Drinking Water ActSafe Drinking Water Act (1974) requires minimum safety standards for every community water supply

• Also has provisions to protect groundwater

WATER QUALITY TODAY

• Watershed approaches are involving local people and getting them informed about what goes on in their watersheds awareness about their effects on the local water quality

• Since 1998, EPA uses a TMDL system to regulate input of pollutants

Remaining Problems

• Greatest impediments to achieving national goals in water quality are sediment, nutrients, and pathogens, especially from non-point discharges.– About three-quarters of water pollution in the

US comes from soil erosion, air pollution fallout, and agricultural and urban runoff.

• Single cow produces 30 kg manure/day.– Some feedlots have 100,000 animals.

Problems and Progress in Other Countries

• Sewage treatment in wealthier countries of Europe generally equal or surpass the US.

• In Russia, only about half of the tap water supply is safe to drink.

• In urban areas of South America, Africa, and Asia, 95% of all sewage is discharged untreated into rivers.

• Two-thirds of India’s surface waters are contaminated sufficiently to be considered dangerous to human health.

Ocean Pollution

• Estimated 6 million metric tons of plastic bottles, packaging material, and other litter tossed from ships into the ocean annually.– Few coastlines in the world remain

uncontaminated by oil or oil products.

• London Dumping Convention (1990)– International convention– Calls for end to ocean dumping– U.S. is a signatory to this