Water Use – Instream vs. Offstream vs. Consumptive
Definitions
• Consumptive use:
use, but don’t return
(ag. products) 1995:
US = 100 bgpd
• In-stream use: used in
source (navigation,
hydro, recreation)
• Off-stream use: use
and return (irrigation,
livestock, etc.)
Trends in Water Usage
Surface water
withdrawals exceed
ground water withdrawals
Water withdrawals
leveled off ~1980, but
population has continued
to increase = better water
management practices
Thermoelectric is greatest
fraction of use by
category.
Total
Surface water
Ground water
*Figure
has error
in textbook
Wetlands
General term referring to
swamps, marshes, bogs, prairie
potholes, vernal pools.
Operational definition – land that
is either inundated by water or is
saturated to a depth of a few
centimeters for at least a few
days most years.
Perform many functions: buffer
against coastal erosion, natural
filters of sed/nutrients/pollution,
natural sponge – floodwater
storage, habitat for diverse
flora/fauna, groundwater
recharge/discharge regions.
The point – removal of water
“upstream” may decrease
functionality of wetlands.
Threatened Groundwater of
Long Island
Abundant groundwater contained in
two “outstanding” aquifers:
1.Upper, young glacial deposits
yielding abundant supply at
shallower than 30 m depth
2.Lower, interbedded sands, clays,
and silts (the Magothy formation) –
artesian conditions in places.
Problem #1: Population stresses on
supply – groundwater pumping has
decreased fresh water table and
promoted salt water intrusion to
deep aquifer beneath Nassau
county.
Problem #2: Upper aquifer pollution
from urbanization. Landfills located
on permeable sandy soils.
Q: What is water pollution?
A: Degradation of water quality as measured
by bio., chem., or phys. criteria.
Q: What is a pollutant?
A: Any substance of which an identifiable
excess is known to be harmful to desirable
living organisms.
Coral Reefs – An indicator of human pollution?
Hanauma Bay, Oahu, is in
poor ecological shape as a
result of:
1.Oceanic warming
2.Excessive coastal
development
3.Pollution of nearshore waters
Coral reefs thrive in clear,
nutrient-poor waters.
Rising nutrients assist coralpreying organisms.
Sediment (developmental
runoff) blocks sunlight.
60% of world’s coral reefs are
threatened – indicating the
ocean is much more sensitive
than previously thought.
Oxygen-demanding waste
Dead stuff decays, i.e. is consumed by bacteria which need oxygen.
So, in a stream, when there is an excess of dead stuff, the high bacteria activity
needed will lower oxygen levels driving further death (fish, etc.)
What kind of feedback is this? positive or negative?
Commonly measure B.O.D. (Biochemical Oxygen Demand) to assess water quality.
BOD=mg/Liter of Oxygen consumed in 5 days at 20˚ C
Pathogenic Organisms
Waterborne Human diseases: cholera, typhoid
infections, hepatitis, dysentery
Monitor pathogens by a proxy – human fecal
coliform bacteria
• common constituents of human intestines
and waste
• most, but not all, are harmless
Examples:
* E. coli outbreak of 1993 – contaminated meat
from Jack-in-the-Box franchises around the
western US (Wash., Calif., Nevada, Idaho)
* 1993 – 400,000 cases of cryptosporidiosis
near Milwaukee
Waterborne illness still kills thousands outside
the U.S. where separation of sewage and
drinking water is not well-practiced.
Nutrients
Phosphorus & Nitrogen – two examples
Related to land use
Released from fertilizers, detergents, and sewage treatment plants.
High concentrations result in eutrophication – rapid increase in abundance of
plant life/algae, which block sunlight, killing plants below, which drives higher
B.O.D. further killing living organisms in natural waters.
Nutrients
In Hawaii, marine eutrophication along the coast, resulting from agricultural
practices may be killing the goose that has laid the golden egg – the beaches are
becoming covered with dead algae that has washed up on shore to rot and serve
as a home for irritating insects.