Environmental Geology Spring 2010
– Text Notes
Water Supply and Use
Groundwater supplies over 50% of our drinking water needs in the
World Water Sources:
Ocean
97.2%
Glaciers
2.15%
Groundwater 0.61%
Lakes
Fresh
0.009%
Saline
0.008%
Soil Moisture 0.005%
Atmosphere 0.001%
Rivers
0.0001%
World Fresh Water:
Ice and Glaciers
85%
Groundwater
14%
Lakes and Reservoirs 0.6%
Soil Moisture
0.29%
Water Vapor
0.05%
Rivers
0.004%
Residence Time:
Oceans
Thousands of years (average if
there is such a thing is about 5000 years)
Atmosphere about
9 days
Rivers
about 2 weeks
Groundwater hundreds to many
thousand years
Lakes
tens of years
Ice and Glaciers may be tens of thousand of years
Look over components of hydrologic cycle in your text:
Confined and Unconfined Aquifers:
Unconfined: water table is open to receive recharge (pressure at water table is
equal to atmospheric pressure). Unsaturated zone overlies the water
table. Below the water table is the zone of saturation (saturated zone).
Confined: by definition pressure is greater than atmospheric pressure therefore
water will rise above the top of the aquifer unit. The primary water
bearing unit is confined (sandwiched) between lower permeability units (confining
units). If pressure is sufficient to cause the water to flow at the
ground surface then it is known as a flowing artersian
system.
Effluent (gaining) and Influent (losing) streams
Effluent streams gain flow from the adjacent groundwater reservoir. Often
this is sufficient to maintain flow in these streams throughout the year (even
when no recent precipitation has occurred).
Influent streams lose water through infiltration and feed the underlying
groundwater reservoir. We see examples of this in many of the streams
throughout the karst region of northwest
Water Budget: Just like your checkbook (It’s supposed to
balance!!). Inputs = outputs
Main input is atmospheric moisture
Part of this falls as precipitation.
Of this, some infiltrates, some runs off, and some evaporates, and some is
transpired by plants and animals.
In the
If we divide this by the mid-1990’s
We went over the exercise in class to show that each of us uses about 120
gallons per day for our personal household needs not including car washing and
lawn watering. The remainder of the 385 gallons/day consists of water used for
the products we consume such as milk, steak, paper, etc.
A recent article by the U.S. Geological Survey indicates that when water used
for power generation is included the per capita use in the
Instream Use:
• Navigation
• Power generation (pass through the turbines)
• Fish and wildlife maintenance
• Recreation
• Water quality maintenance
Offstream Use:
Irrigation
• Municipal and domestic supply
• Industrial supply
• Power generation (cooling water that evaporates)
• Livestock water
Consumptive vs. non-consumptive Use:
Consumptive use moves water from one reservoir to another while
non-consumptive use puts the water to use without changing the physical, or
chemical characteristics of the water. Off stream uses tend to be
consumptive uses while instream uses tend to be
non-consumptive uses.
Groundwater depletion:
Looked at a map of
Agriculture is the largest water user, public supply is second, and self
supplied industrial is third.
The Ogallala Aquifer has over 168,000 irrigation wells that irrigate over 16
million acres of land. Over 23 million acre-feet of groundwater is
withdrawn from this aquifer annually which accounts for about 30% of the
groundwater used for irrigation in the
Dams and Reservoirs:
Purpose:
• Flood Control
• Navigation
• Recreation
• Water supply (both irrigation and municipal use)
• Power generation
Looked at cross section of a reservoir illustrating various pools within the
reservoir including the sediment pool, upper and lower conservation pools, and
the area designated for flood control.
Water Conservation:
Estimated that we can save about 20% to 30 % of current use through
conservation.
Home:
Low water use landscaping (xeriscaping)
• Rock
• Cactus
• Painted
Graywater Use
• House plants
• Lawns
Low flow toilets (they really are getting better!!)
Low flow shower heads
Shower with a friend
Drive a dirty car
Price structure to force conservation
Agricultural:
More efficient irrigation
• Drip irrigation (not economically realistic on large
scale row crop production)
• Computer driven sprinkler systems tied to soil
moisture monitors
• Recycle waste water for irrigation use
Change to less water hungry crops
Industry:
• Fix leaks
• Recycle and reuse water in other plant processes
Colorado River:
Make the desert bloom
Supplies 7 states plus Mexico
First formal management 1922 with signed Colorado River Compact
Separated into Upper Basin and Lower Basin
Upper Basin allocated 7.5 million acre-feet/yr; Lower Basin allocated 8.5
million acre-feet/yr; Mexico allocated 1.5 million acre-feet/yr
Original flow estimates based on short period of record during relatively high
period of flow
Actually long term average is about 13 million acre-feet/yr so the result is
the river has been over-allocated by at least 4.5 million acre-feet/yr.
Tribal governments including the Navajo Nation and the Hope Nation made claims
to the water under treaties with the Federal government and have been awarded
substantial water rights in addition to that already allocated to the 7 states
and
Evaporation from large lakes causes increases in salinity that must be dealt
with prior to releasing the flows to
Review slides for alternate water supply options