Test 4 Water Resources & Water Pollution

World’s Water Supply

97.5% salt water, 2.5% fresh water - (1.7% ice) only 0.8% of all water usable - distributed unevenly

Watersheds

surface water and ground water included, area of land that all drains into the same body of water (usually ocean/Amazon/Mississippi) - water soaks into ground like sponge

Groundwater

exists in spaces in permeable layer of rock and sediment called aquifers (un/confined) - recharge very slowly (overdrawn) - used for 50% of water → exists almost everywhere (even dry climates) and can be cheaper but slow recharge leads to overdraws, land sinking and pollution

Confined Aquifer

aquifer capped by an impermeable layer of rock/clay - pressure can build up underground 

Unconfined Aquifer

recharged by precipitation/ water that percolates downwards from land/surface through porous/permeable sediment - Ogallala is the biggest in the US (1/3 of US groundwater)

Artesian Well

formed when a well is drilled into a confined aquifer and the natural pressure causes the water to rise toward surface without a pump

Banking Analogy

Checking Account: Surface water, everyday use

Savings Account: Ground water, in case of emergency (backup plan for events like droughts)

Overdrawing Aquifers

tend to use GW in dry climates where the surface water doesn’t replenish quickly, lots of big cities and arid farming climates  - very large amounts used for irrigation in these dry climates - can cause a cone of depression and/or saltwater intrusion

Watertable

the uppermost level at which the water in a given area fully saturates the rock/soil - considered the surface of groundwater

Cone of Depression

an area where there is no longer reachable groundwater because an adjacent, deeper well is being rapidly withdrawn - lowering water table below the shallower wells - not necessarily illegal

Saltwater Intrusion

rapid pumping of wells drilled in aquifers along a coastline can lower the water table, lowering the pressure and allowing salt water to move into the aquifer and contaminate it w salt - irreversible bc fresh and salt water only separated by density

Surface Water

fresh water that exists above ground (streams,rivers, lakes, etc.)

Floodplains

flat low area next to a river/lake/coast that is subject to flooding - used to be considered beneficial for agriculture now levees and dams hold water back → reduced fertility, soil w less nutrients, sediment pollution in coastal ecosystems (can’t deposit along the way), risks larger floods downstream

Levee

enlarged bank built up on each side of the river to prevent flooding in floodplain 

Dike

built to prevent ocean waters from flooding adjacent land - common in N Europe

Dam

barrier across a river/stream to control the flow of water - water stored in body called a reservoir - built for recreation, flood control, power generation (electricity), irrigation for agriculture, and municipal use

4 Problems of Dams

1. Habitat loss downstream: loss of biodiversity, ecosystem services - 70% of flow removed which leads to wetlands disappearing - Native fish cant migrate properly (food chain effects) fish ladders created to help

2. Human-Induced Seismicity: earthquakes created from weight of water in reservoir 

3. Involuntary displacement of residents: reservoirs flood huge areas of land, homes, buildings and whole towns can be affected (1 mil Gorges Dam, China)

4. Water quality issues in reservoir: large losses of water through evaporation, lots of nutrients and detritus that arent going downstream gather and cause eutrophication → dead zones → anaerobic decomposition → produces methane (greenhouse gas)

Aral Sea Water Diversion

most famous river diversion project, 1950s Soviet Union diverted 2 rivers that fed the sea - dramatically decreased freshwater in sea - salinity destroyed fish populations - reduced surface area by 60+%, split the sea into 2 parts, dust storms took soil from/salt/sediment and made climate more arid/hot in summer and cooler in winter

Human Effect on flooding

increased the likelihood of floods by

• decreasing vegetation - foliage traps/absorbs water - without it, more runoff, soil erosion, lowland flooding 

• increasing impermeable surfaces like concrete that cause more runoff and less groundwater

• insistance on building on floodplains

Desalination

removing the salt from water - 2 ways to do it (distillation and reverse osmosis) - Middle East produces 50% of desal water

Distillation

uses heat to convert pure water into steam - then collected and condensed into pure water - leaving salt behind - uses lots of energy

Reverse Osmosis

uses pressure to force water through a semi-permeable membrane, leaving the salt behind - slightly more efficient/ less energy

Desal Pros

• reverse osmosis getting more efficient

• can support 100s of 1000s of people

• 54 million gals/day/plant

• 840 megawatts/day - could power 30k homes

• water running out and best option available

• More reliable than freshwater/precipitation

Desal Cons

• very expensive

• large infrastructure requirement

• raises water prices ($5 per month)

• releases greenhouse gasses exacerbating climate change and drought

• don’t know long term effects of dumping the collected salt back into ocean (marine animal safety)

• not enough info on environ impacts

Major Uses of Water

majority of freshwater used for agriculture, then industry, then domestic/households

Agricultural Water Use

water used for irrigation and raising livestock, largest global water use, 70+% of human freshwater withdrawal

Industrial Water Use

water used in manufacturing, energy production, mining and processing foods, cooling machinery, generating steam and cleaning - 20% of freshwater - use large amounts of water esp in developed countries

Household/Domestic Water Use

water used in homes for drinking, cooking, bathing, laundry, cleaning and lawn watering - 10% of freshwater use

Water Use in Developed Countries

higher proportion of water for industry and energy production, lower agricultural dependence bc of efficient irrigation and advanced technology

Water Use in Developing Countries

majority of water for agriculture due to reliance on subsistence farming and less efficient irrigation systems

Irrigation

artificial application of water to crops for agriculture, largest driver of freshwater depletion

Furrow Irrigation

water flows thru trenches - low efficiency (33%) - high evaporation and runoff

Flood Irrigation

Entire field submerged, moderate efficiency (55%), high water loss

Spray Irrigation

water sprayed thru nozzles, high efficiency (85%) but energy intensive

Drip Irrigation

Water drips directly to plant roots, highest efficiency (95%), low evaporation/runoff

Privatization of Water

when water supply systems are owned or managed by private companies instead of government/public agencies - controversial due to concerns ab equity, access and profit-driven pricing

Price of Water

higher pricing could be used to encourage conservation by corporations but they might pass on price to the consumer - privatization and scarcity can increase prices affecting affordability and access

Grey Water

relatively clean water/wastewater from baths/showers/sinks/washing machines that cant be used for drinking but suitable for irrigation, washing cars, flushing toilets - great way to conserve water

Low flow Appliances

plumbing devices designed to use significantly less water than standard fixtures without sacrificing performance.

Point Source Water Pollution

pollutants released into water at a specific location (ex: factory wastewater) 

Non-Point Source Water Pollution

precipatation gathers pollutants from large diffuse are of land into water (ex: farming region, suburb, parking lots)

Oxygen Demanding Waste

Organic waste (sewage, manure, food waste) requires oxygen to decompose. Microbial breakdown lowers dissolved oxygen (DO) and can suffocate aquatic life.

Sources: Sewage treatment plants, animal feedlots, manure lagoons, food-processing waste.

Biochemical Oxygen Demand Test

(BOD) Tests for oxygen demanding waste in water - measures the amount of oxygen needed for microbes to break down organic matter 

High BOD = High pollution

Dissolved Oxygen Test

(DO) Tests for oxygen demanding waste in water - amount of oxygen in water available for aquatic organisms 

Low DO = pollution/eutrophication

Nitrogen & Phosphorous

essential plant nutrients that become pollutants when concentrations are too high - fertilizer runoff, manure, wastewater effluent, detergents - cause eutrophication, algal blooms, and eventual dead zones from microbial oxygen consumption

Eutrophication & Dead Zones

Excess nutrients → algal bloom → algae die → decomposers consume oxygen → hypoxic (low O2) waters 

Ex: large dead zone in the Gulf of Mexico from MS river agr runoff

Pathogens

Disease causing organisms (bacteria, viruses, protozoa) in contaminated water - 1/8 people do not have access to safe water - major waterborne illnesses: cholera & hepatitis - from untreated wastewater - use indicator species to see if water is contaminated (fecal coliform bacteria)

Fecal Coliform Test

detects E.coli as an indicator of fecal contamination, high coliform levels = unsafe drinking/ swimming

Water Turbidity

Cloudiness caused by suspended particles; high level harms aquatic plants and indicates erosion/pollution.

Water pH

Measures acidity/alkalinity; extremes harm aquatic life.

Water Total Dissolved Solids

(TDS): Amount of dissolved ions; high TDS may indicate runoff pollution or salinization.

Water Temperature

Warmer water holds less oxygen; increases metabolic stress

Endocrine Disruptors

Chemicals that mimic, alter or block hormones, interfering with endocrine system (growth, reproduction and metabolism)

EDC Sources

plastics (BPA), pharmaceuticals, pesticides, industrial chemicals, flame retardants, treated wastewater, cleaning products, cosmetics, nonsticks, most surface water

EDC Effects

Abnormal reproduction (intersex fish), developmental issues (low IQ), reproductive issues (infertility and low sperm count), preterm birth, cancer (ovarian and breast), thyroid disruption, diabetes, obesity

PCBs (Polychlorinated Biphenyls)

From Old electrical equipment, industry, improper disposal.
- Carcinogen, persistent pollutant, bioaccumulates/biomagnifies, neurological and reproductive damage.

Arsenic

Naturally in groundwater, mining, industrial runoff, old pesticides.
- Cancer, skin lesions, cardiovascular damage; toxic to aquatic life.

Lead

Old pipes, paint, old gasoline, industrial waste.

- Neurotoxin; damages brain, kidneys and nervous system, especially harmful to children’s brain development.

Mercury

Coal burning, mining, waste incineration.
- bioaccumulative in fish → human neurological damage (brain and nervous system)

Pesticides

Agricultural runoff, lawn fertilizers

- endocrine disruption, bioaccumulation, toxic to aquatic life

Acids (Acid Deposition)

SO₂ and NOₓ emissions from coal burning → acid rain.
- Low pH harms fish, dissolves toxic metals into water.

Perchlorates

Rocket fuel, explosives, fireworks.
- Harm thyroid function in humans; persistent in groundwater.

Solid Waste Pollution & Garbage Patches

Trash entering waterways (plastic bottles, bags, microplastics) - Wildlife entanglement, ingestion, chemical leaching

• Ocean gyres (like the Great Pacific Garbage Patch) concentrate floating plastic.

Sediment Pollution

Soil erosion from agriculture, construction, logging.
Effects: Increases turbidity, clogs fish gills, reduces photosynthesis, smothers habitats.

Thermal Pollution

Discharge of warm water from power plants and industry.
Effects: Warm water holds less oxygen; stresses or kills aquatic organisms.

Noise Pollution

Ships, sonar, industrial activity.
Effects: Disrupts marine mammals’ communication and navigation.

Clean Water Act

Regulates pollutant discharges into U.S. surface waters and sets water quality standards. Focus: making waters fishable and swimmable (ecological)

Safe Drinking Water Act

Sets Maximum Contaminant Levels (MCLs) for drinking water to protect human health.

Wastewater Treatment Bar Screens

Physical filters that remove large solids (trash, debris)

Wastewater Primary Treatment

Settling tanks remove suspended solids (sludge) and floating oils/grease (scum)

Wastewater Secondary Treatment

Biological treatment using aeration tanks where microbes break down organic matter; followed by a disinfectant (chlorine, ozone, UV) to kill pathogens.

Wastewater Tertiary Treatment

Advanced treatment to remove nutrients (N, P) or other remaining pollutants; not all plants include this step.

Sludge Treatment

Sludge is thickened → digested by anaerobic bacteria → methane → disposed or used as fertilizer (biosolids)

Septic Systems

Septic tank, drain field (leach field), pipes

Process: Wastewater → septic tank (solids settle & decompose) → effluent flows into drain field → soil filters remaining contaminants.

Stormwater & Storm Sewers

Rainwater runoff that picks up pollutants from streets - sewers direct into nearby waterways without treatment.

Combined Sewer Systems

stormwater and sewage share pipes.
Heavy rain overwhelms system → untreated sewage overflow into waterways

Animal Feedlots & Manure Lagoons

High-density livestock operations producing large manure volumes

• pits storing animal waste; can leak or overflow, contaminating water with nutrients, pathogens, and antibiotics.