Transcript 14.2 Conserving Groundwater

14.2 Conserving
Groundwater
Key Idea:
Groundwater is an important
resource whose availability is
threatened by overuse and by
pollution
We Learn:
1.
2.
3.
What a water budget is.
About some of the causes of
groundwater depletion and sources
of pollution.
How to preserve and protect the
groundwater.
What Is a Water Budget?
The water budget is the balance between
the water that reaches the ground as
precipitations, and the water that leaves
the ground as evaporation, runoff, and
consumption.
 If the amount of precipitation of a region
is greater than the evaporation and
consumption added together, then that
region has a positive water balance, or
surplus.
 If, the amount of precipitation is less than
the usage and evaporation, then the
region has a negative water balance, or

The Water Cycle
Factors Controlling the Water
Budget of a Region
The water budget of a region is
influenced by many natural factors
and human activity. Some of the
natural factors are:
 Climate conditions
 The characteristics of soil
 The type of vegetation
 The type of underlying rocks, etc.
Factors Controlling the Water
Budget of a Region
1.Climate encompasses the
temperatures, humidity, atmospheric
pressure, winds, rainfall, atmospheric
particle count and numerous other
meteorological elements in a given
region over long periods of time, as
opposed to the term weather, which
refers to current activity of these
same elements.
Factors Controlling the Water
Budget of a Region
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When the air temperature is high, plants use
more moisture and in the same time the
evapotranspiration is high.
When the temperature is low, plants may not use
as much moisture, thus the evapotranspiration is
low.
A moisture surplus occurs when the rainfall is
greater than the need for moisture and the soil
water storage is filled. At this point, the soil
moisture is recharged, and the surplus
percolates into the groundwater, rising the water
table.
If the need for moisture is greater than the
rainfall, the plants draw water form the soil; this
is the time for soil water usage.
Groundwater Conservation
 About
50% of drinking water in the
US comes from groundwater.
 Groundwater is a very valuable
resource, and it is in great demand.
 Human use threatens the aquifers in
two ways:
1. overuse
2. pollution
Overuse of Groundwater
If we take out more water than the aquifer
can naturally recharge each year, then the
consequences are dramatic, and in many
cases irreversible:
 Wells can dry, and human communities
have no water!
 In coastal areas, by pumping put the fresh
water, salty water will take its place.
 By removing the water, the rocks become
more compact, and the surface of the
ground sinks . This phenomenon is called
subsidence.
Coastal Wells Salinization
Subsidence

By removing water from the subsoil the
ground becomes more compacted. This is
an unwanted phenomenon for two main
reasons:
- once the porosity of the rocks is lost, the
aquifer can not be recharged.
-secondly, if the ground loses some of its
porosity, it reduces its volume, and sinks.
San Joaquin Valley in California subsided
in some places over 9 yards, only in half
of century.
Methods Used to Fight Overuse
Artificial methods are used to replenish
the aquifers.
 The used household water is pumped
back into the ground through wells.
 Water is also pumped into ponds and
allowed to seep back into the
ground.
Plant to Replenish Groundwater
California
 In
the San Jacinto Valley, dozens of
wells -- some as deep as 1,000 feet
or more -- pump 40,000 to 50,000
acre-feet of water each year, about
10,000 acre-feet more than what
goes in on average.
 As the water table drops, so must
the wells, which means more energy
-- and more money -- is needed to
pump.
Groundwater Pollution
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Groundwater is recharged by rain seeping down
through the soil.
Virtually, any harmful chemical that is disposed at
the surface of the ground will reach the
groundwater.
Some common pollutants are:
-fertilizers and pesticides
-toxic wastes berried in the ground (common
practice in the past)
-accidental spills
-farm wastes
-sewage from septic tanks, etc
Groundwater Use and Pollution
Sources of Groundwater Pollution
Sources of Water Pollution
One Billion people Lack Clean
Drinking Water
Reducing Groundwater Pollution
There is no simple or inexpensive way
to purify polluted groundwater.
Further pollution can be controlled,
or reduced by:
 Reducing the use of pesticides and
fertilizers
 Using environmental friendly
chemicals in agriculture
 Proper disposal of toxic wastes.
Household Toxic Chemicals
What should we do with them?
Proper Disposing of Hazardous
Wastes