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Freshwater Resources: Natural

Systems, Human Impact, and

Conservation

Chapter 15 Part 2

Environmental Science

Freshwater pollution and its control

• Water for human consumption and other

organisms needs to be…

• disease-free
• nontoxic
• Half of the world’s major rivers are seriously

depleted and polluted

• they poison surrounding ecosystems
• threaten the health and livelihood of people
• The invisible pollution of groundwater has been

called a “covert crisis”

Eutrophication is a natural process, but…

• Human activities dramatically increase the rate at

which it occurs

Pathogens and waterborne diseases

• Enters water supply via inadequately treated

human waste and animal waste

• Causes more human health problems than any

other type of water pollution

• Fecal coliform bacteria indicate fecal

contamination of water

• the water can hold other pathogens, such as

giardiais , typhoid, hepatitis A

• An estimated 5 million people die per year

Sediment pollution

• Sediment can impair aquatic ecosystems

• clear-cutting, mining, poor cultivation practices
• dramatically changes aquatic habitats, and fish may

not survive

• Solutions:
  • better management of farms and forests
  • avoid large-scale disturbance of vegetation

Thermal pollution

• Warmer water holds less oxygen

• dissolved oxygen decreases as temperature increases
• industrial cooling heats water
• removing streamside cover also raises water

temperature

• Water that is too cold causes problems

• water at the bottom of reservoirs is colder
• when water is released, downstream water

temperatures drop suddenly and may kill aquatic

organisms

Indicators of water quality

• Scientists measure properties

of water to characterize its

quality:

• biological indicators : presence of fecal coliform bacteria and other disease-causing organisms
• chemical indicators : pH, nutrient concentration, taste, odor, hardness, dissolved oxygen
• physical indicators : turbidity, color, temperature

Groundwater pollution is a serious

problem

• Groundwater is increasingly contaminated, but is

hidden from view

• difficult to monitor
• “out of sight, out of mind”
• retains contaminants for decades and longer
• takes longer for contaminants to breakdown in

groundwater because of the lower dissolved oxygen

levels

Agriculture and industries pollute groundwater

• Agricultural pollution comes from several sources
  • Pesticides are in most of the shallow aquifers tested
  • Nitrates from fertilizers have caused cancer,

miscarriages, and “blue-baby” syndrome

• Pathogens like Escherichia coli ( E. coli )
• Manufacturing industries and military sites have

been heavy polluters

• By-products seep into water from miles around
• Radioactive wastes will contaminate water for

750,000 years

Legislative efforts reduce pollution

• Federal Water Pollution Control Act (1972)

• Renamed the Clean Water Act in 1977
  • illegal to discharge pollution without a permit
  • standards for industrial wastewater
  • funded sewage treatment plants

• Because of legislation, the situation is much

better than it was