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Chapter 13. Section 5 – 6 – 7 . Gabriela Aguiar & Maria Fernanda Suarez. Is converting salty seawater to freshwater the answer? . Chapter 13 Section 5 . We can convert salty ocean water to freshwater BUT the cost is high , VERY COSTLY

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chapter 13

Chapter 13

Section 5 – 6 – 7

Gabriela Aguiar & Maria Fernanda Suarez

is converting salty seawater to freshwater the answer
Is converting salty seawater to freshwater the answer?

Chapter 13Section 5

  • We can convert salty ocean water to freshwater
      • BUT the cost is high, VERY COSTLY
      • The resulting salty brine must be disposed of without harming aquatic or terrestrial ecosystems.
  • Removal of dissolved Salts and other minerals from the sea water to make it domestic use.
      • Distillation
      • Reverse Osmosis (Microfiltration)
one method of desalination distillation
One method of Desalination:Distillation

This is an example of how the process occurs

      • Heating water until it evaporates leaving behind the salts and condenses as fresh water.
  • The action of purifying a liquid by a process of heating and cooling.
another method of desalination reverse osmosis microfiltration
Another method of Desalination:Reverse Osmosis (Microfiltration)

This is an example of how the process occurs

Uses high pressure to force saltwater through a membrane filter with pores small enough to remove salt.

removing salt water from seawater seems promising but is costly
Removing salt water from seawater seems promising but is costly
  • Desalination: involves removing dissolved salts from ocean water or from brackish (slightly salty) water in aquifer or lakes for domestic use.
      • Distillation: is a method for desalinating water. Heating water until it evaporates leaving behind the salts and condenses as fresh water.
      • Reverse osmosis ( microfiltration): is another method. Uses high pressure to force saltwater through a membrane filter with pores small enough to remove salt.

Did you know?

Saudi Arabia has the world’s largest number of desalination plants.

The United States has the world’s second greatest desalination capacity.

three major problems with desalination
Three major problems with Desalination
  • 1. High cost and high energy footprint.
      • It takes a lot of energy to desalinate water with distillation requiring about ten times as much energy as reverse osmosis requires.
  • 2. Pumping large volumes of seawater through pipes and using chemicals to sterilize the water and keep down algal growth
      • kills many organisms.
  • 3. Desalination produces a large number of briny wastewater that contains lots of salts and other minerals.
      • This makes increase the salinity of ocean waters.
chapter 13 section 6
Chapter 13Section 6
  • We can use water more sustainably by
  • cutting water waste
  • Raising water prices
  • Slowing population growth
  • Protecting aquifers, forest and other ecosystems that store and release water

How can we use water more sustainably?

reducing water waste has many benefits
Reducing water waste has many benefits.
  • Improving water use efficiency would:
    • Decrease the burden on wastewater plants
    • Reduce the need for expensive dams and water transfer projects that destroy wildlife habitats and displace people.
    • Slow depletion of ground water aquifers
    • Save both energy and money.
the causes of water waste why do we have water waste
The causes of Water waste“WHY DO WE HAVE WATER WASTE?”
  • 1. The main cause of water wastes is

Its low cost to users

    • Underpricing is mostly the result of government subsides that provide irrigation water, electricity, and diesel fuel used by farmers to pump water from rivers and aquifers at below-market prices.
    • Because these prices are low, users have no incentive on investing in water-saving technology.
      • 2. The second major cause of water waste is:

A lack of government subsides for improving efficiency of water use.

we can cut water waste in irrigation
We can cut water waste in Irrigation
  • Irrigation: the artificial application of water to the land or soil.
    • It is used to assist in the growing of agricultural crops, maintenance of landscapes, etc..
  • About 60% of the irrigation water applied throughout the world does not reach the targeted crops.
flood irrigation method

Delivers far more water than is needed for crop growth and typically loses 40% of the water through evaporation., seepage, and runoff.

This wasteful method is used on 97% of China’s irrigated land.

drip or trickle irrigation microirrigation method
Drip or Trickle Irrigation MICROIRRIGATION METHOD:
  • The most efficient way to deliver small amounts of water precisely to crops.
    • It consist of a network of perforated plastic tubing installed at or below the ground level.
  • Current drip irrigation systems are costly BUT they drastically reduce water wastes; 90-95% of the water input reaches the crops.
  • It is used on just over 1% of the world’s irrigated crop fields
    • 4% of those in the United States.
      • This percentage rises to
        • 90% in Cyprus,
        • 66% in Israel, and
        • 13% in California.
developing countries use low tech methods for irrigation
Developing Countries Use Low-Tech Methods for Irrigation
  • Rainwater harvesting:
    • another simple and cheapest way to provide water for drinking and for growing crops throughout most of the world. (for irrigation)
we need to use water more sustainably
We need to use water more Sustainably

“The frog does not drink up the pond in which it lives.”

lets change the world

Each of us can help to bring about such a

blue revolution by using less water and cutting our water waste to reduce our water footprints.

The solution starts with:

thinking globally and acting locally.

chapter 13 section 7
Chapter 13 Section 7
  • We can lessen the threat of flooding by
  • By protecting more wetlands and natural vegetation in watersheds
  • By not building in areas subject to frequent flooding.

How can we Reduce the Threat of Flooding?

some areas get too much water from flooding
Some Areas get TOO much Water from Flooding.
    • Floodplain

-A flood happens when water in a stream overflows its normal channel and spills into the adjacent area.

  • Floods provide several benifits:
    • They have created the world’s most productive farmland by depositing nutrient-rich silt on floodplains.
    • Recharge groundwater and help refill wetlands, thereby supporting biodiversity and ecological services.


removal of water absorbing vegetation
Removal of Water-absorbing Vegetation

Human activity. (Especially on hillsides)

case study pg 339
Case Study! Pg.339

Living Dangerously on Floodplains in Bangladesh

we can reduce flood risks
We can reduce flood risks:
  • Channelizing streams reduces upstream flooding.
    • BUT it also:
      • Eliminates aquatic habitats
      • Reduces groundwater discharge
      • Results faster flow

Which can increase downstream flooding and sediment deposition.

reduce flooding
Reduce flooding
  • One of the most important ways to reduce flooding is
    • To perserve existing wetlands
    • Restore graded wetlands
    • To take advantage of the natural flood control they provide in floodplains.
  • This helps protect biodiversity and to restore degraded ecological services provided by these awuatic ecosystems.
flood risks


Many poor people live in flood-prone areas because they have no where else to go.