Water Resources
Chapter 12
This lecture will help you understand:
Water’s importance to people and ecosystems
Aquatic systems
Use of aquatic systems
Water supply problems and solutions
Water pollution
Water quality legislation
Wastewater treatment
Ocean fisheries
Marine protected areas
Central Case Study: Starving the Louisiana Coast of Sediment
Louisiana’s vital coastal wetlands
Support biodiversity
Protect the coast from storms
Mississippi River sediments:
Keep soil levels high, water stable, and plants healthy
Wetlands are shrinking
Dams stop sedimentation
Levees prevent water from spreading into the delta
Why are Louisiana’s wetlands disappearing?
Oil and gas extraction promote wetland losses
Withdrawal compacts land and lowers soil levels
Canals fragment wetlands and increase erosion
Oil spills destroy vegetation
Diverting the Mississippi River
Can restore the wetlands
Will cost millions
Freshwater systems
Water may seem abundant, but drinkable water is rare
Fresh water is relatively pure, with few dissolved salts
Most is tied up in glaciers, ice caps, and aquifers
Water is renewed and recycled
Water is renewed and recycled by the water cycle
The water cycle creates a web of interconnected aquatic systems
The water cycle
Groundwater plays a key role
Groundwater is water beneath the surface held in pores in soil or rock
20% of the Earth’s supply of fresh water
Aquifers are porous, spongelike formations of rock, sand, or gravel that hold water
A typical aquifer
The Ogallala Aquifer
The world’s largest known aquifer
Unsustainable withdrawals are depleting the aquifer
Its water has allowed farmers to create the most bountiful grain-producing region in the
world
Surface waters: rivers and streams
Surface water is on Earth’s surface
1% of freshwater
Runoff is water that flows over land
Water merges in rivers and ends up in a lake or ocean
Watershed is the area of land drained by a river and its tributaries
We build dikes and levees to control floods
Flooding is a normal, natural process where water spills over a river’s banks
Spreads nutrient-rich sediments over large areas
Dikes and levees (long, raised mounds of earth) along the banks of rivers hold water in
channels
Dikes and levees make floods worse by forcing water to stay in channels, which then
overflow
Lakes and ponds are ecologically diverse
Great Lakes
20% of the world's supply of surface water
95% of the North American supply of surface freshwater
We are draining rivers and lakes
In many places, we are withdrawing water at unsustainable rates
Major rivers (e.g., the Colorado) run dry before reaching the sea
The Aral Sea was once the world’s fourth largest sea
It lost 80% of its volume in 45 years
The Aral Sea
The two rivers leading into the Aral Sea were diverted to irrigate cotton fields
60,000 fishing jobs are gone
Ponds and lakes change over time
Oligotrophic lakes and ponds have low-nutrient and high-oxygen conditions
They can transform into …
Eutrophic lakes and ponds have high-nutrient and low-oxygen conditions
Eutrophication can also result from human-caused nutrient pollution
Freshwater wetlands
Wetlands are diverse and productive systems
Wetlands: the soil is
saturated with shallow,
standing water
Freshwater marshes: shallow
Swamps: shallow water in
forested areas
Bogs: ponds covered in thick
floating mats of vegetation
Vernal pools: adapted to seasonal drying
Wetlands are valuable
Wetlands are extremely valuable for wildlife
They provide important ecosystem services:
They slow runoff, reduce flooding, recharge aquifers, and filter pollutants
People have drained wetlands, mostly for agriculture
The U.S. has lost over half of its wetlands
Ohio has lost 90% of wetlands
Oceans are complex
Oceans touch and are touched by every system - they receive all inputs, sediment,
pollutants, organisms
Oceans cover 71% of Earth and hold 97% of surface water
Surface water is warmer than subsurface water
Warmed by the sun and is less dense
Deeper water is dense and sluggish
Unaffected by winds, storms, sunlight, and temperature
Ocean water flows horizontally in currents
Currents are vast river-like flows in the upper 1,300 feet
Driven by wind, heating/cooling, gravity, density differences, and the Coriolis effect
Ocean water also flows vertically
Upwelling is the rising of cold, deep water to the surface
Rich in nutrients
High primary productivity and lucrative fisheries
Downwelling is the sinking of warm, oxygen-rich water
Provides oxygen for deep-water life
A stylized bathymetric profile of the ocean
Regions of the ocean differ greatly
Currents affect climate
Movement of ocean water affects global climate
Thermohaline circulation: a worldwide current system
Warmer, fresher water moves along the surface
Colder, denser, saltier water moves below the surface
North Atlantic Deep Water (NADW): one part of this system
Warm water from the Gulf Stream flows across the Atlantic Ocean, warming Europe
Water cools, becomes saltier, and sinks
Creating a region of downwelling
Gulf Stream
NADW circulation and climate change
El Niño (ENSO)
El Niño–Southern Oscillation (ENSO): a shift in
Normally, winds blow westward
“Piling up” water in the western Pacific
Deep, cold water rises and brings up nutrients
Peru and Ecuador have rich fisheries
Decreasing air pressure in the eastern Pacific
Triggers El Niño
Suppresses upwelling on the America’s Pacific coast
Devastates fisheries and costs billions of dollars
Causes heavy rain in Americas
Normal vs. El Niño conditions
Freshwater meets saltwater in estuaries
67% of all people live within 100 miles of the ocean
Estuaries are water bodies where rivers flow into the ocean
Shallow water nurtures plants that provide critical habitat for shorebirds and shellfish
Estuaries are affected by development, pollution, habitat alteration, and overfishing
Salt marshes line temperate shorelines
High primary productivity provides critical habitat for birds and commercial fish and shellfish
species
Salt marshes occur along
coasts at temperate latitude
Filter pollution and stabilize shorelines
Mangrove forests occur in the tropics
Mangrove forests line sandy coasts in tropical and subtropical latitudes
Mangroves are salt-tolerant trees with unique roots
Habitat for fish, shellfish, birds
Protect coastlines from storms
Filter pollutants, stabilize soils, protect coral reefs
50% of mangroves have been destroyed for resorts or shrimp farms
Life abounds in the intertidal zone
Kelp forests harbor many organisms
Kelp are large brown algae growing from the floor of continental shelves along temperate
coasts
Kelp can grow to 200 ft tall, forming “forests”
Provide shelter and food for organisms
Absorb wave energy and protect shorelines from erosion
Kelp serves as food and as thickeners in cosmetics, paints, paper, and soaps
Coral reefs are treasure troves of biodiversity
Corals are tiny organisms living in shallow subtropical or tropical waters
Derive nourishment from symbiotic algae (zooxanthallae)
Coral reefs protect shorelines
by absorbing waves
Reefs have staggering
biodiversity and are valuable ecotourism destinations
Corals are experiencing alarming declines
Nutrient pollution promotes algal growth, smothering corals
Coral bleaching: zooxanthellae die or leave corals
Results from warmer water from climate change, pollution, eutrophication
Ocean acidification occurs when oceans absorb excess CO2
Lowing the pH of seawater
Reducing carbonate ions
and dissolving calcium
carbonate in shells
Water is unequally distributed across Earth
Water is unevenly distributed in space and time
Different areas possess different amounts of water
People are not distributed according to fresh water
Water-Rich and Water-Poor Countries
Water availability usually measured in terms of renewable water per capita
Highest per capita generally found in countries with moist climates and low population
densities
Quantities of water used
Human water use has been increasing about twice as fast as population growth over the
past century
Americans use 1,300 gallons per person per day, while Haitians use 8 gallons per person per
day
Quantities of water used
Worldwide, agriculture claims about 70% of total water withdrawal
In many developing countries, agricultural water use is extremely inefficient and highly
consumptive
Worldwide, industry accounts for about 20% of all water use
Cooling water for power plants is single largest industrial use
Domestic water use accounts for 10% of water withdrawals
American water use
Domestic conservation
Estimates suggest many societies could save as much as half of current domestic water
usage without great sacrifice or serious change in lifestyle
Low-volume shower heads
Efficient dishwashers and washing machines
Landscape choices
Waterless or low-volume toilets
A precious resource
Currently, ~45 countries, most in Africa or Middle East, are considered to have serious water
stress, and cannot meet the minimum essential water requirements of their citizens
More than two-thirds of world’s households have to retrieve water from outside the home
Sanitation levels decline when water is expensive
Depleting groundwater
Groundwater is the source of nearly 40% of fresh water in the U.S.
On a local level, withdrawing water faster than it can be replenished leads to a cone of
depression in the water table
On a broader scale, heavy pumping can deplete an aquifer
Ogallala Aquifer, which once held more water than all the freshwater lakes, streams, and
rivers on earth, has fallen dramatically
Depleting groundwater
Withdrawing large amounts of groundwater in a small area causes porous formations to
collapse, resulting in subsidence
Sinkholes form when an underground channel or cavern collapses
Saltwater intrusion can occur along coastlines where overuse of freshwater reservoirs draws
the water table low enough to allow saltwater to intrude
Increasing water supplies
Dams, reservoirs, canals and aqueducts
Common to trap excess water in areas of excess and transfer it to areas of deficit
China’s Three Gorges Dam
On the Yangtze River
$39 billion to build
Flooded 22 cities
Displaced 1.24 million
Submerged old sites
Drowned farmland and habitat, eroded marshes
Eroding tidal marshes
Provides flood control, passage for boats, electricity
Water wars?
Solutions can address supply or demand
Reducing demand is already paying off
From 1980 to 2005, the U.S. population grew 31%, but water consumption decreased 5%
Point and nonpoint sources of pollution
Pollution: the release of matter or energy that causes:
Undesirable impacts on health and well-being of humans or other organisms
Water pollution has many forms and can cause diverse impacts on aquatic ecosystems and
human health
Point sources
Discharge pollution from specific locations
Factories, power plants
Easy to control through regulations (Clean Water Act)
Non-point sources
Non-point sources - Scattered or diffuse, having no specific location of discharge
Agricultural fields, feedlots
Very difficult to monitor and regulate
Water pollution sources
Infectious agents
Biological pollution causes more human health problems than any other type of water
pollution
Main source of waterborne pathogens is improperly treated human waste
Animal wastes from feedlots and fields is also important source of pathogens
Infectious agents
Biodegradable wastes or oxygen-demanding wastes
Biodegradable materials decrease dissolved oxygen in water
Human waste, animal manure, paper pulp, yard wastes (grass clippings, leaves), food waste
Bacterial decomposition lowers dissolved oxygen
Wastewater: humans release biodegradable wastes
From toilets, sinks, dishwashers, washing machines, industrial cleaning processes,
stormwater runoff
Developed nations treat wastewater
Many developing nations don’t treat wastewater
Oxygen sag
Nutrient pollution
Nutrient pollution from fertilizers, farms, sewage, lawns, golf courses leads to
eutrophication and hypoxia
Excess nitrogen and phosphorus in water boosts algal and aquatic plant growth
Algal blooms cover the surface, decreasing sunlight
Bacteria eat dead plants, reducing dissolved oxygen
Solutions include treating wastewater, reducing fertilizer application, and using phosphatefree detergents
Eutrophication
Eutrophication is a natural process, but…Gulf of Mexico hypoxia
In 1974, scientists found areas where oxygen had disappeared from bottom sediments and
the water column
Hypoxic area in 1993 after Mississippi floods doubled in size
Influx of nitrogen from Midwest/Great Plains is cause
Hypoxic area continues to grow
Harmful algal blooms (HABs)
HABs have become increasingly common in slow-moving and shallow waters, usually due to
pollution
Algal blooms produce toxins
Red tides are blooms of deadly aquatic algae
Cryptosporidium in 1993 entered the Milwaukee public water supply, making 400,000
people sick and killing at least 100 people
Toxic chemicals
Pesticides, petroleum products, synthetic chemicals
Toxic metals (arsenic, lead, mercury), acid rain, acid drainage from mines
Effects include poisoned animals and plants, altered aquatic ecosystems, and human health
problems
Solutions:
Issue and enforce more stringent regulations of industry
Modify industrial processes
Modify our purchasing decisions
Pesticide runoff
Pollutants contaminate groundwater
Groundwater pollution is hard to detect and address
It retains contaminants for decades and longer
It takes longer for contaminants to break down because of lower sunlight, microbes, and
dissolved oxygen
Pollution from human activities leaches through soils
Agricultural nitrates cause “blue baby syndrome”
By leaking underground storage tanks, improperly designed wells, and storage of hazardous
wastes
Groundwater pollution
Sediment pollution
Sediment in rivers can impair aquatic ecosystems
Clear-cutting, mining, clearing land for housing, and cultivating farm fields expose soil to
erosion
It dramatically changes aquatic habitats
Impairs organism respiration
Fish may not survive
Cloudy water blocks sun, killing rooted plants
Solutions: adopting better soil practices
Avoid large-scale disturbance of vegetation
Keep riparian vegetation to trap sediments
Sedimentation
Thermal pollution
Raising or lowering water temperatures from normal levels can adversely affect water
quality and aquatic life
Water that is too warm causes problems
Warmer water holds less oxygen
Cooling an industrial facility with water heats water, which heats a river when it is released
Removing streamside cover raises water temperature
Water that is too cold also causes problems
Water at the bottom of reservoirs behind dams is colder
When water is released, downstream water temperatures drop suddenly, killing aquatic
organisms
Oil pollution
Few coastlines in the world remain uncontaminated by oil or oil products
Estimated 3-6 million metric tons of oil are discharged into the world’s oceans
Transport creates opportunities for major spills
Oil pollution
Large spills are infrequent but can be devastating
Other sources include:
Natural seepage, boat leakage, road and parking lot runoff
Spills during transport and leakage during extraction
In 2010, the Deepwater Horizon drilling platform exploded
Killing 11
Spilling 1,800 gallons/min
Polluting Louisiana, Mississippi, Alabama, Florida
Oil spills have decreased
Oil spills have decreased
Due to an emphasis on spill prevention and response
The U.S. Oil Pollution Act of 1990
$1 billion prevention and cleanup fund
All ships must have double hulls by 2015
Oil pollution
Ocean pollution
Estimated 6 million metric tons of plastic bottles, packaging material, and other litter tossed
from ships into the ocean annually
Nets and plastic debris
Plastic items dumped into the sea harm or kill wildlife
Fishing nets, plastic bags and bottles, fishing line, buckets, floats
Mammals, seabirds, and sea turtles eat plastic and die
Converging ocean currents accumulate plastic trash
North Pacific’s Great Pacific Garbage Patch
Congress passed the Marine Debris Research, Prevention, and Reduction Act in 2006
Minimize this harm by reducing, reusing, and recycling plastic
Great Pacific Garbage Patch
3.5 million tons of trash
Size of Texas
Water pollution control
Source reduction
Cheapest and most effective way to reduce pollution is avoid producing it or releasing it into
the environment
Studies show as much as 90% less road salt can be used without significantly affecting
winter road safety
Soil conservation
Consumers can purchase sustainably made products
Legislative efforts reduce pollution
Water pollution was worse decades ago
The Federal Water Pollution Control Act (1972)
Renamed the Clean Water Act in 1977
Made it illegal to discharge pollution without a permit
Set standards for industrial wastewater
Funded building of sewage treatment plants
Focus on making water bodies “fishable” and “swimmable”
Municipal sewer systems
In populated areas, municipal sewer systems carry wastewater to wastewater treatment
plants
Primary treatment removes suspended solids
Secondary treatment occurs when water is stirred and aerated
Aerobic bacteria degrade organic pollutants
Clarified water treated with chlorine (or ultraviolet light)
Effluent (treated wastewater) is discharged into rivers or the ocean, or may be used for
lawns, irrigation, or industry
A typical wastewater treatment facility
Sludge: solid material resulting from treatment
Is decomposed microbially
Then landfilled, incinerated, or used as fertilizer
Artificial wetlands clean wastewater
Microbes “polish” treated wastewater
Removing plant nutrients (N and P)
Cleansed water is released into waterways
We are emptying the oceans
People are overharvesting marine species
Half of the world’s marine fish populations are fully exploited
25% of fish populations are overexploited and heading to extinction
With current trends, populations of all ocean species we fish for will collapse by 2048
Total fisheries catch leveled off after 1998
Despite increased fishing effort
Fishing has industrialized
The total global fisheries catch has stalled
Industrialized fishing uses several methods
Industrialized fishing depletes fisheries
Oceans contain only 10% of the large-bodied animals they once held
Many fisheries have collapsed, destroying fishing economies
Groundfish (e.g., cod, haddock, halibut, flounder) stocks collapsed in the Grand Banks in
Canada
Consumer choices can encourage sustainable fishing
Marine reserves protect the ocean
Marine protected areas (MPAs): established along the coastlines of developed countries
Still allow fishing or other extractive activities
Marine reserves: areas where fishing is prohibited
Leave ecosystems intact, without human interference
Improve fisheries—young fish disperse into surrounding areas
Reserves work—species density, biomass, size, and diversity all increased 1–2 years after
establishment