Chapter 13

Gabriela Aguiar & Maria Fernanda Suarez

Section 5 – 6 – 7

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 • 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)

Desalination

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.

One method of Desalination:Distillation

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.

Another method of Desalination:Reverse Osmosis (Microfiltration)

This is an example of how the process occurs

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.

Removing salt water from seawater seems promising but is costly

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

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

Did you know?

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.

Three major problems with Desalination

How can we use water more sustainably?

Chapter 13 Section 6

We can use water more sustainably by o cutting water wasteo Raising water priceso Slowing population growtho Protecting aquifers, forest and other

ecosystems that store and release water

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.

Reducing water waste has many benefits.

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.

The causes of Water waste“WHY DO WE HAVE WATER WASTE?”

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.

We can cut water waste in Irrigation

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.

FLOOD IRRIGATION 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.

Drip or Trickle Irrigation MICROIRRIGATION METHOD:

Solutions for Reducing Irrigation Water Waste

Rainwater harvesting: another simple and cheapest way to provide

water for drinking and for growing crops throughout most of the world. (for irrigation)

Developing Countries Use Low-Tech Methods for Irrigation

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

We need to use water more Sustainably

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.

LETS CHANGE THE WORLD

How can we Reduce the Threat of Flooding?

Chapter 13 Section 7

We can lessen the threat of flooding by By protecting more wetlands and

natural vegetation in watershedsBy not building in areas subject to

frequent 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.

FLOODS KILL THOUSANDS OF PEOPLE EACH YEARAND CAUSE TENS OF BILLIONS OF DOLLARS IN PROPERTY DAMAGE.

Some Areas get TOO much Water from Flooding.

Human activity. (Especially on hillsides)

Removal of Water-absorbing Vegetation

LIVING DANGEROUSLY ON FLOODPLAINS IN BANGLADESH

Case Study! Pg.339

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.

We can reduce flood risks:

We can reduce flood risks:

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.

Reduce flooding

THINK CAREFULLY OF WHERE WE CHOOSE TO LIVE

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

FLOOD RISKS