1

Water: Resources and Pollution

"Water will be more important than oil this century.”- Former U.N. Secretary General Boutros Boutros Gali

Transformation of Nature

• A network of irrigation canals were built to divert water from two rivers into a desert region, to encourage the cultivation of crops such as rice, wheat, and cotton.

• The rivers normally fed into the Aral Sea.

2

The Aral Sea

• In the 1950s, the Aral sea was one of the four largest lakes in the world, with an area of 26,300 square miles.

• The entire lake was part of the U.S.S.R., in the countries that today are Kazakhstan and Uzbekistan.

3

Irrigation Canals

• The irrigation canals were poorly built and uncovered, allowing about half of the water to evaporate or leak into the surrounding soil.

• The Aral sea, deprived of its main water supply, began to shrink in 1961.

4

Satellite imagery of the Aral Sea shrinkage from 1961-2011.

Salination

• The amount of water lost by the Aral Sea would completely fill Lakes Erie and Ontario.

• The salinity of the remaining water has increased to 2-3x that of ocean water.

• The drainage of the lake has also exposed pesticides, herbicides, and other industrial pollutants on the bottom. 5

An abandoned ship in Aral, Kazakhstan.

Why is Water Important?

• Necessary for all life to exist.• Next to antibiotics, single biggest increase in

human life span is due to having access to clean water.

• Diseases/toxins transmitted by contaminated water: Intestinal disease (cholera/dysentery) Arsenic poisoning Mercury poisoning

6

7

Hydrologic Cycle

• The water on earth is continually recycled.• The hydrologic cycle describes this circulation:

1. Water evaporates from wet land, lakes, or oceans and transpires from plants as they dry up.

2. Enters the atmosphere, which is much colder, condenses and falls as precipitation.

3. Moves underground by infiltration or runs off into rivers, lakes, or the ocean.

8

Fig. 11-2, p. 238

All water

Oceans andsaline lakes97.4%

Earth’s Water Budget

Fig. 11-2, p. 238

All water

Oceans andsaline lakes97.4%

Earth’s Water Budget

Fig. 11-2, p. 238

All water Fresh water Readily accessible fresh water

Oceans andsaline lakes97.4%

Fresh water2.6%

Groundwater0.592%

Ice capsand glaciers1.984%

Soilmoisture0.005%

Biota0.0001%

Rivers0.0001%

Atmosphericwater vapor0.001%

0.014%

Lakes 0.007%

Earth’s Water Budget

12

MAJOR WATER COMPARTMENTS

• Groundwater Largest available (non-frozen) source of fresh

water. Water moves underground through infiltration;

percolation through the soil and into fractures and permeable rocks.

- Zone of Aeration - Upper soil layers that hold both air and water.

- Zone of Saturation - Lower soil layers where all spaces are filled with water.

- Water Table - Top of Zone of Saturation

13

Infiltration

14

Groundwater

• Aquifers - Porous layers of sand, gravel, or rock lying below the water table. Aquifers are separate from groundwater;

they are usually isolated by layers of rock. Artesian Well – Directly tapes into an

aquifer as a source of water.

15

Groundwater

• The recharge zone is an area where water infiltrates and refills an aquifer. Recharge rate is often very slow,

depending on the size of the recharge zone and how often it rains there.

16

MAJOR WATER COMPARTMENTS CONT’D

• Wetlands Play a vital role in hydrologic cycle.

Wetlands have an unusually high amount of plant growth. Benefits include:

- Stabilizes soil, preventing erosion- Slows down surface runoff, allowing

more aquifer recharge.- Can hold excess water during flooding.

17

MAJOR WATER COMPARTMENTS CONT’D

• Rivers and Streams Formed from water that does not infiltrate,

but runs off from surrounding land. May also be formed by melting glaciers.

Each of the major rivers in Southeast Asia are fed by Himalayan glaciers.

18

MAJOR WATER COMPARTMENTS CONT’D

• The Atmosphere Among the smallest water reservoirs; only

contains 0.001% of the total water supply. Has most rapid turnover rate. Water in the

atmosphere does not remain there.- Redistributes water all over the earth.

19

Water Use

• Consumption – Water that is withdrawn and no longer available for use because it has evaporated, been consumed by animals or plants, or discharged to a different location.

20

Quantities of Water Used

• Water use has been increasing twice as fast as population growth over past century. Worldwide, agriculture claims about 70%

of total water withdrawal.- In many developing countries,

agricultural water use is extremely inefficient and highly consumptive.

Worldwide, industry accounts for about 25% of all water use.

- Cooling water for power plants is single largest industrial use.

21

Water Withdrawal

22

INCREASING WATER SUPPLIES

• Seeding Clouds • Add silver iodide or dry ice to clouds• Inconsistent results

• Towing Icebergs Cost

• Desalination Removal of salt

from ocean water Requires a high

input of energy

23

INCREASING WATER SUPPLIES

24

INCREASING WATER SUPPLIES CONT’D

• Dams, Reservoirs, and canals can be constructed to make the water supply more consistent or divert water to dry areas. This could result in the displacement of

people, flooding of ecosystems. Evaporation rates increase as water is

slowed. Any dissolved nutrients present in the water

sink into the reservoir.

26

Water Quality Today

Source: US EPA http://pubs.usgs.gov/fs/FS-130-01/

Water Testing Standards

• The EPA requires that local water treatment plants provide yearly reports to residents listing any contaminants found in the drinking water supply.

• Must be tested for microbes several times a day. Bottled water has much less strict

requirements.

27