Water Resources

Chapter 9

Read these notes and the first and last parts part of Chapter 9 in your text (For this course you are responsible for 4CE pages 240-256 and 265-270 / 3CE pages 232-246 and 254-259; we do the middle of the chapter,  “Groundwater” [4CE pp. 256-265 / 3CE pp.246-254] in the other course :)).

There is an introductory video here:  http://youtu.be/9fXO4fR1Qp0

Elihu says to Job:  “Look, God is exalted beyond what we can understand. His years are without number.  He draws up the water vapor and then distills it into rain.   The rain pours down from the clouds, and everyone benefits from it.   Can anyone really understand the spreading of the clouds and the thunder that rolls forth from heaven?   See how he spreads the lightning around him and how it lights up the depths of the sea.

By his mighty acts he governs the people, giving them food in abundance.   He fills his hands with lightning bolts.   He hurls each at its target.   The thunder announces his presence; the storm announces his indignant anger.”

 Job 36:26-33 NLT

I know the greatness of the LORD – that our Lord is greater than any other god.
The LORD does whatever pleases him throughout all heaven and earth, and on the seas and in their depths.
He causes the clouds to rise over the earth.   He sends the lightning with the rain and releases the wind from his storehouses.
Psalm 135:5-7 NLT

Nearly three quarters of the world’s surface is covered in water. Yet less than 3% of the world’s water supply is freshwater, and two-thirds of those resources are trapped within icecaps and glaciers “fossil” water).  How much freshwater is actually available for human use (“renewable” water)?  Less than 1% of all water on the planet.

Water is a renewable but finite resource.  Continually cycling from the atmosphere to the earth and back to the atmosphere, there is the same amount of water now as when the Earth was formed. However, only a small portion of the freshwater in lakes and aquifers is renewed each year from rainfall and snowmelt.  For example, it is estimated that only about 1% of the water in the Great Lakes is renewed annually.

So each year, there is a little less fresh water available.  In addition, population growth, ever-rising demand, and environmental pollutants are increasingly threatening this all-important resource.

As of 2015, according to estimates from the United Nations, at least 40% of the world’s population, or about three billion people, will live in countries where it is difficult or impossible to get enough water to satisfy basic needs.

9 Water_Cycle_(v1.10)

The hydrologic cycle (footnote 1)

I. The Hydrologic Cycle

Water in the Earth-atmosphere system is continually susceptible to transfer from the oceans, lakes, streams, groundwater, atmospheric water vapour, etc.  The hydrologic cycle refers to the whole system of water movement through the Earth-atmosphere system.

Water goes through all 3 states within the hydrological cycle – solid, liquid, gas.  Water is the only compound on earth that exists in all 3 states naturally.

  • Study Figure 9.4, “The hydrologic cycle model” (4CE, p. 245 / Figure 9.1 3CE p.235 ).

Environment Canada has an excellent page on the hydrologic cycle:   Environment Canada – Water – The Hydrologic Cycle.

The U.S. Geological Survey also has an excellent diagram of the hydrologic cycle.

A.  Inputs into the Global Hydrologic Cycle

1. Precipitation (PRECIP)

Precipitation can be measured using gauges.  However it can also be considered in terms of where the water which falls as precipitation goes.

Precipitation, when it reaches the earth’s surface moves into other aspects of the hydrologic cycle including the soil, plants, streams, rivers, and oceans.

  • Some precipitation will be evapotranspired (evaporated from and transpired by plants).
  • Some precipitation will runoff (directly flowing into streams, rivers, and lakes) as a surplus.
  • Some precipitation will soak into the ground as groundwater storage.

2.  Other inputs

Some water also enters a given region as groundwater and runoff (often in the form of streams or rivers) from other regions.  These are often balanced by outputs of groundwater/runoff as well (thus STRG represents the change in soil-water storage).  Normally input from groundwater and runoff is balanced by outputs of runoff and groundwater.

These represent inputs to the cycle.  In order for balance to be maintained, they must equal inputs …

B.  Outputs from the Hydrologic Cycle

  1. Evapotranspiration (POTET, ACTET, DEFIC)

The combined water loss from direct evaporation and the transpiration of plants is referred to as evapotranspiration

Evaporation is simply the process whereby water on the surface is evaporated into water vapour by energy (directly or indirectly) from the sun.  Evaporation will continue as long as there is moisture at the surface and the air is not yet saturated.

Transpiration occurs when stomata, small pores on plants, open under the influence of sunlight and release water from within the plant into the atmosphere by evaporation.  Plants use solar energy to evaporate water from their leaves.  This results in the leaves “drying out.”  As the leaves dry out, the plant draws up moisture from the soil through its roots and stem, into the leaves.  Water is drawn up through the plant from the roots.  This process transports nutrients throughout the plant.  This, in turn, feeds the plant.  The moisture which is drawn from the soil is rich in dissolved nutrients that the plant needs to survive.  Plants have to transpire to survive.  This is the mechanism they use to bring dissolved nutrients in the soil into their roots, and then throughout the plant.

Because evaporation and transpiration are intimately connected, they are usually grouped together and referred to as evapotranspiration.  Almost everywhere moisture is present for evaporation, plants are also present, so transpiration occurs.  And whenever plants transpire moisture, it must be evaporated.  The two processes are, in reality, almost always combined.

The rate of evapotranspiration drops as surface soil water is reduced (there is less water for plants to use).  And the rate of evapotranspiration drops as  plants become moisture stressed (they wilt!) and close their stomata.  This is why you have to keep your plants watered or they die!  Evapotranspiration is also dependent on sunlight.  This is why your plants needs light!  Direct sunlight is not always necessary or desirable (depending on the plant), but every plant needs light to drive the evapotranspiration pump process in order to absorb nutrients from the soil!  If a plant does not have light, it does not evapotranspire … and it dies!

There are two aspects of evapotranspiration:

a. Potential evapotranspiration (POTET) measures how much water the atmosphere could potentially remove from the surface assuming no limitation of water supply.  Given unlimited water supply, this is the potential amount of moisture that could be evapotranspired.  This is a theoretical figure.

POTET is primarily related to the amount of insolation a location receives.  It therefore varies with latitude, day-length, cloudiness, and pollution.

  • POTET is greatest in clear, hot weather in the tropics.
  • POTET is least in cold, cloudy polar regions.
  • POTET will be 0 during Arctic winters when there is no insolation.

In a daily basis, POTET is minimal at night and greatest shortly after peak insolation in daytime.

Seasonally, POTET is greatest in summer in mid-latitudes, and least in winter.

If you think this through a bit, the highest potential evapotranspiration will be in regions that receive a lot of insolation (remember earlier in the course).  For instance along the equator, there is much insolation all year round, therefore there would be much POTET all year round.  In our region, we get much insolation in the summer, therefore we would have high POTET in the summer.  However we receive little insolation in the winter; therefore lower POTET in the winter.

Remember POTET simply refers to potential evapotranspiration, given unlimited water resources.  The reality is that in many regions water is NOT unlimited!  Therefore the amount of water that actually evapotranspires might be much less!

b. Actual evapotranspiration (ACTET) is the amount of water that is actually evaporated.

ACTET will only equal POTET if there is enough water so that the atmosphere can constantly evaporate moisture.

If there is not enough water, the atmosphere will not be able to evaporate all the moisture it could.  POTET (the potential amount the atmosphere could evaporate) would exceed ACTET (the amount actually evaporated).  In this case, some solar energy which could be used to evapotranspire moisture is “wasted.”

In reality, POTET often exceeds the actual water supply (ACTET) during the hottest times of the day and year.  There is either not enough water to achieve maximum potential evapotranspiration.  Or water cannot be evapotranspired fast enough.  For instance … think of the Arizona/Nevada desert in summer.  There is a tremendous POTET:  lots of insolation, clear skies, etc.  But there is no water!  Therefore, ACTET will be very small!  The same is true of summer conditions in the Canadian Prairies:  POTET is high, but ACTET is relatively small because there simply is not enough water!

Note that ACTET may be less than or equal to POTET.  But ACTET can never exceed POTET (POTET is the maximum evapotranspiration that could possibly occur).  It is impossible for more actual evapotranspiration (ACTET) than the amount of evaporation that is possible (POTET).

When POTET exceeds ACTET, the difference is called a deficit (DEFIC).  The deficit represents the water that could have been evapotranspired by the insolation, but which was not evapotranspired because the water supply was limited.  This can be thought of as “excess” or “wasted” energy.  It is energy that could potentially have been used for evapotranspiration, but a limited water supply prohibited the maximum possible evapotranspiration.

2. Change in Soil Water Storage (+/- STRG)

The amount of soil water in a region can change throughout the year.

a. When the amount of precipitation is large enough so that more rain falls than can be evaporated (it’s really wet!)(PRECIP > POTET and, thus ACTET), the amount of water stored in the ground will increase.  This is groundwater recharge.  This means that the water will stored in the soil (+STRG).

In our region this typically happens through late fall until mid spring. You may notice the ground seems to get wetter and muddier during this time of year.  The water is absorbing more and more water (both from precipitation and melt water runoff).  The amount of water stored in the ground is increasing.

If the ground is saturated, the extra water will run off on the surface.  Every soil has a maximum amount of water it can hold.  Once it is saturated, the extra water runs off.  Different soils have different moisture storage capacities:  these are determined by the composition of the soil (Chapter 18).  In general, soils with a high clay and low sand content can hold more moisture than soils with a low clay and high sand content.

b. If the amount of water being evaporated from the soil exceeds the amount of incoming precipitation (it’s relatively dry!) (ACTET > PRECIP), the result is that the soil dries out.  The amount of water in the soil decreases.  Soil water is evaporated by the sun faster than it is recharged either by precipitation or by melt water runoff.  In this case soil water storage decreases (-STRG).

In our region this typically happens from mid spring through mid fall.  You may notice the ground gets drier and drier during this time of year.  The sun is shining, “sucking out” moisture through evapotranspiration, but there is not enough water in the soil to keep the plants healthy.  In this condition plants may experience “moisture stress.”    Ultimately plants may not be able to continue to evapotranspire at all because they cannot obtain water through their roots.  The result, of course, is wilting, lower plant productivity, and ultimately death.  To prevent this we add groundwater by sprinkling!  Irrigation is one attempt to increase this STRG component to prevent soil reaching the wilting point.

3. Surplus (SRPL) or Runoff

 Soil which is saturated (already holds as much water as it possibly can) or impermeable (no air spaces to allow water in) causes a surplus.  When rain falls, the water runs off the surface into streams, rivers, or lakes.

 III. Soil Water Budgets

All this information can be used to create a soil water budget for a particular location.  A soil-water balance equation can be created for any local area to indicate this:

PRECIP = ACTET + SURPL +/- STRG

PRECIP:           is precipitation (how much water comes into the area from the atmosphere)

ACTET:             is actual evapotranspiration

(water which returns directly to the atmosphere through evaporation or transpiration by plants within the area)

SURPL:            is water surplus (water which runs off into streams/rivers and leaves the area)

+/- STRG:         is change in soil-water storage (water which is added to or removed from the soil)

So … if 100 mm of rain falls on your farm, you can track what happens to it. 

  • Some (let’s say 30 mm) is evapotranspired directly back into the atmosphere. 
  • Some (say 40 mm) runs off into the local stream, and runs off to the river. 
  • Some (let’s say 30 mm) soaks into the ground and recharges the groundwater in your drought parched fields. 
  • Thus all 100 mm are accounted for!

        PRECIP (100 mm) = ACTET (30 mm) + SURPL (40 mm) + STRG (30 mm)

Notice the equation balances (100 mm on each side).  Thus we can account for all the moisture on your farm!

ACTET (actual evapotranspiration) can be further broken down into POTET (potential evapotranspiration) and DEFIC (a moisture deficit) … see below:

ACTET = POTET – DEFIC

POTET is potential evapotranspiration (how much water could be evapotranspired by the incoming solar radiation, if there were an unlimited  supply of water)

DEFIC is soil moisture deficit (often there is not enough water in the area to allow for maximum evapotranspiration (POTET).  Therefore, there is a “deficit” … the amount of incoming solar radiation that is “wasted” because there is not enough water (either PRECIP or groundwater storage (STRG)) in the area to be evapotranspired.

So … back to your farm.  30 mm is actually evapotranspired (ACTET) directly into the atmosphere.  This comes from water evaporated from puddles, ponds, etc. and transpired by plants.  (During the summer, however, the hot sun has the potential to evapotranspire more than 30 mm!  It could potentially evapotranspire 40 mm (my hypothetical number): POTET.  However there is not enough water to provide all 40 mm.  This leaves a deficit of 10 mm that could potentially be evapotranspired but is not, because there is not enough moisture in the system:  DEFIC.

         ACTET (30 mm) = POTET (40 mm) – DEFIC (10 mm)

Notice the equation balances (30 mm on both sides)

  • Study the Sample water budgets in your text:  4CE figure 9.11 / 3CE figure 9.9, “Sample water budget,” and 4CE figure 9.12 / 3CE figure 9.10, “Sample water budgets for selected locations.”

Here’s a more realistic example:

Consider this hypothetical location, we’ll call Sillyville:

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
PRECIP 50` 40 30 20 20 10 10 20 20 30 40 50
POTET 10 10 20 30 40 50 50 40 30 20 10 10
ACTET 10 10 20 30 40 40 30 20 10 20 10 10
DEFIC
-STRG
+STRG
SRPL

NOTE:

  • Sillyville has more precipitation in the winter than summer.
  • POTET is highest during the summer.  This is what we would expect in the Northern Hemisphere. During the summer the Northern Hemisphere is tilted toward the sun.  The days are longer than in the winter; the sun is more intense than in the winter.  More insolation is received in the summer than in the winter.  Thus, more potential evapotranspiration could occur in summer than winter.
  • ACTET is the same as POTET from January until May, and October until December.  During January, for instance, the sun could potentially evaporate 10 mm of water, and actually does evaporate 10 mm. There is enough moisture from precipitation to allow maximum potential evapotranspiration to actually occur:  POTET = ACTET.
  • From June through September, more energy is available to evapotranspire moisture (POTET) than moisture is available to be evapotranspired (ACTET).  During June, for instance, the sun could potentially evaporate 50 mm of water, but it only able to actually evaporate 40 mm.  There is not enough precipitation and groundwater to provide all 50 mm to the atmosphere.

This difference between POTET and ACTET during these months is the deficit (DEFIC):  energy that is essentially “wasted” – it could have been used for evapotranspiration, but there was not enough moisture.

  1. Calculating DEFIC (POTET – ACTET)

The next step in creating a soil moisture budget is to calculate the deficit (DEFIC).  The deficit refers to the “wasted” solar energy – the amount of water that potentially could have been evaporated but was NOT actually evaporated, because there was not enough water in the system.

DEFIC = POTET – ACTET:

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
PRECIP 50` 40 30 20 20 10 10 20 20 30 40 50
POTET 10 10 20 30 40 50 50 40 30 20 10 10
ACTET 10 10 20 30 40 40 30 20 10 10 10 10
DEFIC 0 0 0 0 0 10 20 20 20 10 0 0
-STRG
+STRG
SRPL
  • Note that from October through May, DEFIC is 0: as much moisture as could potentially be evaporated is actually evaporated (POTET =ACTET).
  • From June to September, POTET exceeds ACTET.  There is a deficit.  The deficit is calculated simply by subtracting ACTET from POTET.

2. Calculating  – STRG

We can also determine -STRG.  In months where the amount of actual evapotranspiration (ACTET) exceeds the amount of precipitation (PRECIP) – more moisture is evapotranspired than falls as precipitation – the additional moisture that is evaporated must come from somewhere!  If more water is being evaporated than falling as rain, moisture must be coming from a source other than rainfall.  It is, in fact, coming from the ground.

This extra moisture represents a reduction in groundwater storage (-STRG).  The ground is drying out.

For instance, in April, ACTET is 30 mm. PRECIP is only 20 mm.  Therefore 10 mm must come from groundwater (-STRG).

So, in months where ACTET is greater than PRECIP … – STRG = ACTET – PRECIP

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
PRECIP 50` 40 30 20 20 10 10 20 20 30 40 50
POTET 10 10 20 30 40 50 50 40 30 20 10 10
ACTET 10 10 20 30 40 40 30 20 10 10 10 10
DEFIC 0 0 0 0 0 10 20 20 20 10 0 0
-STRG 0 0 0 10 20 30 20 0 0 0 0 0
+STRG
SRPL
  • Note that there is only –STRG during the months where ACTET > PRECIP. This means that groundwater storage is only reduced when more water actually evapotranspires than falls as precipitation; the extra moisture evapotranspired comes from the ground.

For instance, in May, 40 mm is evapotranspire, but only 20 mm falls as precipitation.  The other 20 mm has to come from the ground.

  • Months were PRECIP is greater than or equal to ACTET, there is no –STRG.  There is plenty of precipitation to evapotranspire, so no moisture needs to be drawn out of the ground.

For instance, in January, 50 mm of precipitation falls, but only 10 mm is actually evapotranspired.  No moisture needs to be drawn out of the ground; there is plenty of precipitation to provide the 10 mm to be evaporated.

  • Note that the total –STRG for the year is 80 mm.  (10 + 20 + 30 + 20)

3. Calculating  +STRG

We just calculated that, over the course of the year, 80 mm of water is removed from the soil by evapotranspiration.

Annual  –STRG  = 80 mm.

Over the course of a year, the same amount of water has to be added back into the soil, in order for the system to be stable.  Otherwise the soil would become drier and drier, year after year.

So … +STRG (increase in groundwater storage) must also equal 80 mm for the year.  This will balance the equation for the year.

For the year,  +STRG must equal –STRG.

Otherwise the system gets out of balance and the soil dries out!

Look at September.  In September, more rain falls as precipitation (PRECIP) than is actually evapotranspired (ACTET):  PRECIP > ACTET.  20 mm falls, only 10 mm is evapotranspired.  Where does this extra rain go?  Into the soil as groundwater storage!  Through the summer the soil had been drying out, because more and more water was evapotranspired and very little fell as rain.  In September, more is falling as rain than is being evapotranspired.  The extra can begin to recharge the groundwater storage.

The extra rainfall for the next few months will recharge the groundwater storage, up to a total of 80 mm – the amount withdrawn during the summer as –STRG.  At that point the soil is saturated, and no more water can go into it as +STRG.

So, from September on we’ll calculate +STRG as the excess rainfall over and above what evaporates as evapotranspiration.

+STRG = PRECIP – ACTET

However we need to keep a running total of this +STRG, because it must only equal 80 mm (the total removed the previous summer).

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
PRECIP 50` 40 30 20 20 10 10 20 20 30 30 40
POTET 10 10 20 30 40 50 50 40 30 20 10 10
ACTET 10 10 20 30 40 40 30 20 10 10 10 10
DEFIC 0 0 0 0 0 10 20 20 20 10 0 0
-STRG 0 0 0 10 20 30 20 0 0 0 0 0
+STRG 10 20 20 30
SRPL
  • Note that by December we have reached a total of 80 mm (10 + 20 + 20 + 30).  Thus all the excess rainfall from September through December goes to recharge groundwater storage.
  • At the end of December, however, the groundwater is completely recharged.  The amount put back in (+STRG) is now equal to the amount removed the previous summer (-STRG).  The ground is now saturated.  No further moisture can be added to it.
  • Therefore all the other months will have a +STRG of 0.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
PRECIP 50` 40 30 20 20 10 10 20 20 30 30 40
POTET 10 10 20 30 40 50 50 40 30 20 10 10
ACTET 10 10 20 30 40 40 30 20 10 10 10 10
DEFIC 0 0 0 0 0 10 20 20 20 10 0 0
-STRG 0 0 0 10 20 30 20 0 0 0 0 0
+STRG 0 0 0 0 0 0 0 0 10 20 20 30
SRPL
  • Note that more rain falls in January (PRECIP = 50) than evaporates (ACTET = 10), but the ground is already saturated.  This extra moisture cannot go into the ground.  The ground is holding as much as it possibly can.  For January, +STRG = 0.

4. Calculating SRPL

Once the groundwater storage has been completely recharged (+STRG = -STRG), the excess rain that falls must go somewhere!  It runs off as a surplus (SRPL).  It will run off into a river, a lake, or the ocean.  That is the only possibility.

In January, when PRECIP = 50 and ACTET = 10, the extra 40 mm cannot go into the ground because the ground is saturated.  That 40 mm simply runs off as a surplus (SRPL).

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
PRECIP 50` 40 30 20 20 10 10 20 20 30 30 40
POTET 10 10 20 30 40 50 50 40 30 20 10 10
ACTET 10 10 20 30 40 40 30 20 10 10 10 10
DEFIC 0 0 0 0 0 10 20 20 20 10 0 0
-STRG 0 0 0 10 20 30 20 0 0 0 0 0
+STRG 0 0 0 0 0 0 0 0 10 20 20 30
SRPL 40 30 10 0 0 0 0 0 0 0 0 0
  • Note that SRPL only occurs after the annual groundwater storage (+STRG) has become equal to annual groundwater loss (-STRG).
  • As soon as ACTET is equal to or greater than PRECIP (all the rain is evaporated), there is no longer and surplus (From April on, all the rain is evapotranspired).

III.   Creating a Water Budget

We can now put this information for Sillyville onto a graph …

A.     Graphing PRECIP, POTET, and ACTET

See my Water Budget Graph page (PDF)

Remember, for this course you are not responsible for the middle of the chapter, “Groundwater” [4CE pp. 256-265 / 3CE pp.246-254]. We deal with groundwater in 101/1013.  You are responsible for the section “Our Water Supply,” 4CE pp. 265-270 / 3CE pp. 254-259.

Worth reflecting on …

  1. The Victorian poet, Gerard Manley Hopkins, integrated his belief in the Creator with his life in the world, in his poetry.  Poems like “Pied Beauty,” and this one, “God’s Grandeur”, show this beautifully.

The world is charged with the grandeur of God.
It will flame out, like shining from shook foil;
It gathers to a greatness, like the ooze of oil
Crushed. Why do men then now not wreck his rod?
Generations have trod, have trod, have trod;
And all is seared with trade; Bleared, smeared with toil;
And wears man’s smudge and shares man’s smell: the soil
Is bare now, nor can foot feel, being shod.

And for all this, nature is never spent;
There lives the dearest freshness deep down things;
And though the last lights off the black West went
Oh, morning, at the brown brink eastward, springs–
Because the Holy Ghost over the bent
World broods with warm breast and with ah! bright wings.

Do you have a reaction to this poem?  Feel free to discuss this reading on the course discussion site …

IV. Our Water Supply

Humans use water in all sorts of ways!

Currently humans use 30% of all the runoff (water flowing in streams and rivers) that is accessible.  Some runoff is too remote to access practically.  For instance, most of the Amazon river — the largest river in the world in terms of runoff — is too remote to be useful!  It is not near the major population centers of the world (China, India).

50% of all runoff occurs in the form of floods, which is largely unusable.

Therefore, only about 20% of runoff is still available for human use before runoff is 100% accounted for.  Of that 20%, we cannot practically or possibly use all of it!  If we were to use all of this 20%, rivers and streams would essentially cease to flow!

Canada has 7% of the world’s renewable fresh water.  It is easy to assume that we have an almost endless supply of clean, fresh water.  Canada has 20% of the world’s total freshwater resources.  However, less than half of this water – about 7% of the global supply – is “renewable” (that is, usable).  13% is “fossil” (non-renewable) water retained in lakes, underground aquifers, and glaciers.  For Canada’s 30 million people – about half a percent of the world’s population – this is still a generous endowment. But, more than half of this water drains northward into the Arctic Ocean and Hudson Bay. As a result, it is unavailable to the 90% of the Canadian population who live within 300 kilometers of the country’s southern border. That means the remaining supply, while still abundant, is heavily used and often overly stressed.
In some river systems (for instance the Bow-Oldman-South Saskatchewan River system in southern Alberta) as much as 80% of the runoff is used for human and agricultural (irrigation) use.

Some water use is instream use – water is not removed from the river at all, but used for human purposes:  hydroelectric generation, waste treatment and removal, transportation, recreation.

Some water use is nonconsumptive use – water is removed, some is consumed, but some is also returned:  for instance agriculture, industrial uses, domestic uses (your shower and toilet!).

Some water use is consumptive use – water is removed and is consumed, not returned:  water vaporized in steam electric plants, bottled, or exported.

Even though water may be still in the system through instream and noncunsumptive uses, the amount of water may be reduced.  And the quality of the water may be dramatically altered by human uses.  For instance, only some water used for agriculture will be returned to the stream system (some will evaporate, some be consumed by plants, some consumed by animals).  Of the water that does return to stream, it may be contaminated by chemicals from fertilizers or animal waste.  Downstream communities inherit less water than upstream cities … and water of much poorer quality!

If you have a choice, live as far upstream (close to the source) as possible!  And ensure your community has good water quality testing and treatment!  If your water is supplied from a well, have the water quality tested regularly.  Groundwater is easily contaminated by fertilizers, animal waste, and other noxious chemicals.  As you may learn (or already have learned) in 101/1013, groundwater travels!  Pollutants from one area can easily travel to your well!

See Water pollution – Wikipedia, the free encyclopedia

Water supply issues are becoming big news items — consider the problems and issues in recent years:

As you read this section, reflect on how you can:

  •  reduce your water consumption
  •  reduce your water pollution

There are three golden rules of water conservation – reduce, repair, and retrofit:.

  • Reduce:  It’s surprising how much water gets wasted. We just let it run down the drain. Become conscious of the amount of water you’re using and look for ways to use less whenever you can.
  • Repair:  A leak of one drop per second wastes 10 000 litres of water a year. Most leaks are simple to find and easily fixed, at low or no cost.
  • Retrofit:  Retrofit means adapting or replacing an older, less water efficient fixture or appliance with one of the many water saving devices now on the market.

Some practical ideas:

At work/school

  • Turn off all taps when not in use
  • Report leaking taps or toilets
  • Encourage the us of water-efficient devices
  • Place rubbish in bins and not down the sink or toilet
  • Ask questions about things like landscaping choices, utility use, etc.

At home

  • Fix leaking taps and toilets
  • Install a water-efficient showerhead and an aerator for taps
  • Take shorter showers – most use 10-20 litres of water per minute (take showers, NOT baths!)
  • Replace your toilet with a low flow/dual flush toilet
  • Turn the tap off when brushing your teeth, shaving, cleaning dishes or preparing food except when you need the water running
  • Do not disposing of solvents, cleaners or chemicals down drains.
  • Keep a jug of water in the fridge rather than letting the tap run to get cold water for each drink.
  • Make sure your dishwasher and washing machine are completely full before starting them – dishwashers use about 35 litres of water each run, whilst washing machines consume about 120 litres of water for a full load of laundry
  • Sweep paths and driveways with a broom, not with a hose
  • Use mulch to retain water in the soil
  • Plant native grasses for lawns – they require much less water and mowing
  • Don’t over-water your lawn. Use an automatic timer to avoid puddles and runoff
  • Water your garden during the early morning, to prevent evaporation
  • Wash the car on the lawn (not on the street or driveway) using a bucket, not a hose (use environmentally friendly detergent, don’t use harsh chemicals!
  • Shovel the snow from your driveway/sidewalk onto your lawn/garden … it will recharge the soil moisture!

The Government of Canada has a good wise water use site.

Sydney, Australia, has a great website on how you can use water wisely at home, work, and in your garden … Water in your home

Water supply issues are become a challenge everywhere:  BBC News – Europe’s water resources ‘under pressure’

Water is a precious resource:  people in long- and short-term relief and development work know that water is often one of the most critical factors in community development.

To reflect on …

Taking care of the environment is one of the most important things we can do, says astronomer Jennifer Wiseman (director of NASA’s Hubble Space Telescope programme), and is something that Christians in particular should be concerned about.  Where do you science and your faith lead you in terms of stewardship of the environment? – YouTube

A brief video, “Science involves faith” with Michael, PhD in enhanced oil recovery.

To review …

Remember you are not responsible for the groundwater sections

Check out the resources at www.masteringgeography.com

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Scripture quotations marked (NLT) are taken from the Holy Bible, New Living Translation, copyright © 1996. Used by permission of Tyndale House Publishers, Inc., Wheaton, Illinois 60189. All rights reserved

  1. Water Cycle: By Ehud Tal (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons