14.2 Conserving 14.2 Conserving GroundwaterGroundwater

Key Idea:Key Idea:Groundwater is an important Groundwater is an important resource whose availability is resource whose availability is threatened by overuse and by threatened by overuse and by

pollutionpollution

We Learn:We Learn:

1.1. What a water budget is.What a water budget is.

2.2. About some of the causes of About some of the causes of groundwater depletion and sources groundwater depletion and sources of pollution.of pollution.

3.3. How to preserve and protect the How to preserve and protect the groundwater.groundwater.

What Is a Water Budget?What Is a Water Budget?

The water budget is the balance between the The water budget is the balance between the water that reaches the ground as water that reaches the ground as precipitations, and the water that leaves the precipitations, and the water that leaves the ground as evaporation, runoff, and ground as evaporation, runoff, and consumption. consumption.

If the amount of precipitation of a region is If the amount of precipitation of a region is greater than the evaporation and greater than the evaporation and consumption added together, then that region consumption added together, then that region has a has a positive water balance, or surplus. positive water balance, or surplus.

If, the amount of precipitation is less than the If, the amount of precipitation is less than the usage and evaporation, then the region has a usage and evaporation, then the region has a negative water balance, or deficit. negative water balance, or deficit.

The Water Cycle The Water Cycle

Factors Controlling the Water Factors Controlling the Water Budget of a RegionBudget of a Region

The water budget of a region is The water budget of a region is influenced by many natural factors influenced by many natural factors and human activity. Some of the and human activity. Some of the natural factors are:natural factors are:

Climate conditionsClimate conditions The characteristics of soilThe characteristics of soil The type of vegetationThe type of vegetation The type of underlying rocks, etc.The type of underlying rocks, etc.

Factors Controlling the Water Factors Controlling the Water Budget of a RegionBudget of a Region

1.Climate1.Climate encompasses the encompasses the temperatures, humidity, atmospheric temperatures, humidity, atmospheric pressure, winds, rainfall, atmospheric pressure, winds, rainfall, atmospheric particle count and numerous other particle count and numerous other meteorologicalmeteorological elements in a given elements in a given region over long periods of time, as region over long periods of time, as opposed to the term opposed to the term weatherweather, which , which refers to current activity of these refers to current activity of these same elements. same elements.

Factors Controlling the Water Factors Controlling the Water Budget of a RegionBudget of a Region

When the air temperature is high, plants use more When the air temperature is high, plants use more moisture and in the same time the moisture and in the same time the evapotranspiration is high. evapotranspiration is high.

When the temperature is low, plants may not use When the temperature is low, plants may not use as much moisture, thus the evapotranspiration is as much moisture, thus the evapotranspiration is low. low.

A moisture surplus occurs when the rainfall is A moisture surplus occurs when the rainfall is greater than the need for moisture and the soil greater than the need for moisture and the soil water storage is filled. At this point, the soil water storage is filled. At this point, the soil moisture is moisture is recharged,recharged, and the surplus percolates and the surplus percolates into the groundwater, rising the water table.into the groundwater, rising the water table.

If the need for moisture is greater than the rainfall, If the need for moisture is greater than the rainfall, the plants draw water form the soil; this is the time the plants draw water form the soil; this is the time for soil water for soil water usage. usage.

Groundwater ConservationGroundwater Conservation

About 50% of drinking water in the About 50% of drinking water in the US comes from groundwater. US comes from groundwater.

Groundwater is a very valuable Groundwater is a very valuable resource, and it is in great demand. resource, and it is in great demand.

Human use threatens the aquifers in Human use threatens the aquifers in two ways:two ways:

1. overuse1. overuse

2. pollution2. pollution

Overuse of GroundwaterOveruse of Groundwater

If we take out more water than the aquifer If we take out more water than the aquifer can naturally recharge each year, then the can naturally recharge each year, then the consequences are dramatic, and in many consequences are dramatic, and in many cases irreversible:cases irreversible:

Wells can dry, and human communities Wells can dry, and human communities have no water!have no water!

In coastal areas, by pumping put the fresh In coastal areas, by pumping put the fresh water, salty water will take its place.water, salty water will take its place.

By removing the water, the rocks become By removing the water, the rocks become more compact, and the surface of the more compact, and the surface of the ground sinks . This phenomenon is called ground sinks . This phenomenon is called subsidence. subsidence.

Coastal Wells SalinizationCoastal Wells Salinization

SubsidenceSubsidence

By removing water from the subsoil the By removing water from the subsoil the ground becomes more compacted. This is an ground becomes more compacted. This is an unwanted phenomenon for two main reasons:unwanted phenomenon for two main reasons:

- once the porosity of the rocks is lost, the - once the porosity of the rocks is lost, the aquifer can not be recharged. aquifer can not be recharged.

-secondly, if the ground loses some of its -secondly, if the ground loses some of its porosity, it reduces its volume, and sinks. porosity, it reduces its volume, and sinks. San Joaquin Valley in California subsided in San Joaquin Valley in California subsided in some places over 9 yards, only in half of some places over 9 yards, only in half of century. century.

Methods Used to Fight OveruseMethods Used to Fight Overuse

Artificial methods are used to replenish Artificial methods are used to replenish the aquifers. the aquifers.

The used household water is pumped The used household water is pumped back into the ground through wells. back into the ground through wells.

Water is also pumped into ponds and Water is also pumped into ponds and allowed to seep back into the allowed to seep back into the ground. ground.

Plant to Replenish GroundwaterPlant to Replenish Groundwater

California California

In the San Jacinto Valley, dozens of In the San Jacinto Valley, dozens of wells -- some as deep as 1,000 feet or wells -- some as deep as 1,000 feet or more -- pump 40,000 to 50,000 acre-more -- pump 40,000 to 50,000 acre-feet of water each year, about 10,000 feet of water each year, about 10,000 acre-feet more than what goes in on acre-feet more than what goes in on average.average.

As the water table drops, so must the As the water table drops, so must the wells, which means more energy -- wells, which means more energy -- and more money -- is needed to pump. and more money -- is needed to pump.

Groundwater PollutionGroundwater Pollution Groundwater is recharged by rain seeping down Groundwater is recharged by rain seeping down

through the soil. through the soil. Virtually, any harmful chemical that is disposed at Virtually, any harmful chemical that is disposed at

the surface of the ground will reach the the surface of the ground will reach the groundwater. groundwater.

Some common pollutants are:Some common pollutants are: -fertilizers and pesticides-fertilizers and pesticides -toxic wastes berried in the ground (common -toxic wastes berried in the ground (common

practice in the past)practice in the past) -accidental spills-accidental spills -farm wastes -farm wastes -sewage from septic tanks, etc-sewage from septic tanks, etc

Groundwater Use and PollutionGroundwater Use and Pollution

Sources of Groundwater PollutionSources of Groundwater Pollution

Sources of Water PollutionSources of Water Pollution

One Billion people Lack Clean One Billion people Lack Clean Drinking Water Drinking Water

Reducing Groundwater PollutionReducing Groundwater Pollution

There is no simple or inexpensive way There is no simple or inexpensive way to purify polluted groundwater. to purify polluted groundwater. Further pollution can be controlled, Further pollution can be controlled, or reduced by:or reduced by:

Reducing the use of pesticides and Reducing the use of pesticides and fertilizersfertilizers

Using environmental friendly Using environmental friendly chemicals in agriculturechemicals in agriculture

Proper disposal of toxic wastes.Proper disposal of toxic wastes.

Household Toxic ChemicalsHousehold Toxic ChemicalsWhat should we do with them?What should we do with them?

Proper Disposing of Hazardous Proper Disposing of Hazardous Wastes Wastes