Freshwater resources

1. Freshwater Resources and
Water Pollution

2. Properties of Water
 Molecules of water: H2O
– 2 Hydrogen atoms
– 1 Oxygen atom
 Polar molecule
– One end slightly positive
– One end slightly negative

3. Properties of Water
 Hydrogen bonds that result from water’s
polarity responsible for many of water’s
properties
– High heat capacity
(Moderates climate)
– Universal solvent

4. The Importance of Water
 All living things need
water
 Composes majority of
the body of organisms
 Habitat for many
organisms
 Helps regulate climate
 Shapes earth’s surface
 Dilutes & degrades
wastes

5. Water on Earth
 About 97% Earth’s water is salty–less than 1%
of the planet’s water is available fresh H2O
 Fresh water is distributed unevenly
 2025: 1/3 human population will live in areas
lacking fresh water

6. Water, water, everywhere?
(NOT)
 Comparison of
population sizes and
shares of the world’s
freshwater among the
continents. (Only 7
countries account for
60% of global water
availability)

7. Water Wars
 Many countries in the
Middle East, which
has one of the world’s
highest population
growth rates, face
water shortages.

8. Water wars cont…
 Most water in this dry region comes
from the Nile, Jordan or Tigris rivers.
 Countries are in disagreement as to who
has water rights.
 Currently, there are no cooperative
agreements for use of 158 of the
world’s 263 water basins that are
shared by two or more countries.

9. The Hydrologic
Cycle

10. Surface Water
 Streams, rivers, lakes, ponds,
reservoirs, wetlands
 Runoff replenishes surface water
 Watershed
 Area of land drained by a single river
 What watershed do we live in?

11. Groundwater
 Supply of fresh water found under
Earth’s surface--recharged when water
at surface infiltrates into the ground
 Stored in under
ground aquifers
 Discharged into
rivers, springs,
etc…

12. Infiltration - Process of water percolating
through the soil and into cracks and
permeable rocks.
Zone of Aeration -
Upper soil layers
that hold both air
and water.
Zone of Saturation
Lower soil layers
where all spaces are
filled with water.
Water Table -
Top of zone of
saturation

13. •Recharge Zone - Area where water infiltrates
into an aquifer.
-Recharge rate is often very slow.
-Presently, groundwater is being removed
faster than it can be replenished.
Evaporation and transpiration
Evaporation
Infiltration
Unconfined aquifer
Confined aquifer
Well requiring a pump
Flowing
artesian well
Runoff
Precipitation
Confined
Recharge Area
Less permeable material
such as clay
Confining permeable rock layer
Unconfined Aquifer Recharge Area
Water table

14.  Aquifers - Porous layers of sand, gravel,
or rock lying below the water table.

15. Water Resource Problems
 Too much water
 Too little water
 Poor-quality water

16. Changes in Surface Runoff
 Prior to 1970 about 10%
of stormwater became
runoff
 Now 55% of stormwater
is transported as runoff
as development exceeds
75% of the permeable
soil area

17. Stormwater Runoff
(greatest contributor to nonpoint
source pollution) contains:
 Nutrients*
 Metals*
 Suspended solids*
 Pesticides
 Hydrocarbons
 Microorganisms
*Present in nearly 100% of stormwater
samples

18. Too Much Water
 Heavy rainfall, rapid snowmelt, removal of
vegetation, and destruction of wetlands cause
flooding.
 Floodplains, which usually include highly
productive wetlands, help provide natural
flood and erosion control, maintain high water
quality, and recharge groundwater.
 To minimize floods, rivers have been narrowed
with levees and walls, and dammed to store
water.

19. Human activities have contributed to flood
deaths and damages

20. Too Little Water
 Arid & semiarid lands (growing in
extent -- desertification)
 Irrigation required to produce food
 Greatest use of
water (71%)

21. Aquifer Depletion
 Removing groundwater faster than it is
replenished
 Lowers water table
 Land subsidence
 Saltwater intrusion
 Salt water seeps into
fresh water
 Occurring in
South Florida

22. Overdrawing Surface Waters
 Damaging to ecosystems
 Wetlands dry up (Everglades)
 Estuaries become too salty (FL Bay)
 Worldwide, the demand for water is growing
as the human population and indvidual
consumption continue to grow exponentially
 Water wars
Arial Sea

23. Water Management
 Goal: sustainable supply of high quality
water
 How do we supply water?
 Building dams (ex: Columbia River)
 Diversion (ex: Colorado River)
 Desalination (ex: FL Keys) - very
expensive to build & operate plants

24. Water Conservation: Agriculture
 Single largest user of water worldwide
 Much lost to evaporation or seepage
 Solution: drip irrigation
 Perforated pipes distribute water
 Goes straight to plants
 Reduces water use
40-60%

25. Water Conservation: Municipal
 Solutions:
 Use gray water
 Education: modify habits
 Water-saving fixtures
& Appliances
 Repair leaks
 Cisterns & rain barrels
 Water gardens

26. Water Pollution
 Physical or chemical change in water
that adversely affects the health of
humans or other organisms
 Global problem

27. Eutrophication
 Build up of nutrients in a body of water
 Naturally occurs slowly
 Humans cause imbalances
by creating pulses of
nutrients due to over-
fertilizing crops & lawns
and raising animals in
confined areas
Nutrients include nitrogen and phosphorus-containing
compounds that are essential to life in small quantities
but harmful in excess.

28. Sources of Water Pollution
Nonpoint source
Enters over a large area
Runoff (agriculture or,
urban lawns) or
atmospheric deposition
Point source: specific spot

29. Groundwater Pollution Sources

30. Controlling Water Pollution
1. Source Reduction (Pollution Prevention)
 Cheapest and most effective way to
reduce pollution is to avoid producing
it or releasing it into the environment.
Design products that do not pollute
Soil Conservation
2.Ban release of pollutants
3.Reward purchasing environmentally
preferable products (e.g. rebates)

31. The End