water resources and water pollution -...

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Water Resources And

Water Pollution

Ignacio Hidalgo PittoMaría José Granados Muñoz

Environmental engineering March 2008

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Water Resources1) Water’s importances and

properties.2) Supply, Renewal and use of

water Resources.3) Too litle water: Problems and

Solutions.4) Too much water: Problems

and Solutions.

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We live in a water planet, most of it salt water covering about 71% of the earth surfaces.

All the organism are made up mostly of water:

a tree is about 60 %most animals between 50 – 65 %

Two-thirds of our body is made up of water. We probably drink or should drink 6 - 8 cups of water, milk, fruit juice... each day. So we don't just use

water.... we are water!!!In fact an average healthy man who weighs 70 kg

contains roughly 42litres of water.

pproperties.

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Water's Chemical Propertiesi. As the diagram shows, that is one atom of

oxygen bound to two atoms of hydrogen, resulting in a water molecule.

ii. Pure water has a neutral pH of 7, which is neither acidic nor basic.

iii. Water is called the "universal solvent" because it dissolves more substances than any other liquid.

iv. There are strong forces of attraction called Hidrogen bonds, between molecules of water. It’s a water’s unique properties.

pproperties.

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Water's Physical Propertiesi. Water exists as a liquid over a wide temperature range because of the strong forces

of attraction between water molecules. ii. Water is unique, it is the only natural substance that is found in all three states --

liquid, solid (ice), and gas (steam) -- at the temperatures normally found on Earth. High boiling point of 100ºC (212ºF at sea level, but 186.4° at 14,000 feet) Low freezing point of 0ºC (32ºF)

iii. Water has a high specific heat index. This means that water can absorb a lot of heat before it begins to get hot. This is why It’s very useful in industrial processes, power plant, excellente coolant for engines and also moderates the earth’s climate

iv. Water is called the "universal solvent" because it dissolves more substances than any other liquid.

v. Water has a very high surface tension. Surface tension is responsible for capillary action, which allows water (and its dissolved substances) to move through the roots of plants and through the tiny blood vessels in our bodies.

pproperties.

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and Solutions.

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How much fresh water is available?

2) Supply, Renewal and use of water Resources.

Only a tiny fraction of the planet’s abundant water is available to us as fresh water.

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This works only as long as we do not overload water systems with slowly degradable and nondegradablee wastes or withdraw water from underground supplies faster than it is replenished

Some good news is that theavailable fresh wateramounts is a generoussupply. Moreover this wateris continuously collectedpurified, recycled anddistributed in the solarpowered hydrologic cicle

Global warming can increase global rates of evaporation, shifting precipitation patterns and disrupt water supplies and thus food supplies.

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What is Surface Water?Or Surface RunOff is

precipitation that does not inflitrate the ground or return to the atmosphere by evaporation (including transpiration)

This runoff flows into streams, lakes, wetlands, estuaries and reservoirs.


Watersheld also call a drainagebasin, is a region from wichwater drains into a stream,lake,reservoir, wetland orestuary

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What is Groundwater?Some precipitation inflitrates the

ground and percolates downward through voids (pores, fracture...) in soil and rock. The water in these voids is called Groundwater


Close surface the voids have little moisture.

The Watertable is located at the top of the zone of saturation. It falls in dry weather and rises in wet weather.

Below watertable appear theZone of Saturation where thevoids are filled with water.

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Porous, water-saturated layers of sand, gravel, or bedrock through wich groundwater falls is also called Aquifers


An aquifers is an underground geological formation able to store water. This replenished naturally by precipitation through soil and rock in what is called Natural Rechargebut some are recharged by lateral streams.

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The relation: groundwater and surface water

The groundwater normally moves from points high elevation and pressure to lower points. This movement is quite slow about 0,3 metres per year. Eventually most groudwater flows into rivers, lakes, estuaries, and wetlands. Thus there is a hydrological conection between this two terms, that describe the water’s earth as it circulates through the hydrologyc cicle.


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How much of the World’s Reliable Water Supply Are We Withdrawing?

Resources.

During the last century the human population has tripled this water withdraw.

Accordin to a 2002 report by United Nations, during this period our global water withdrawal (use) increased sevenfold and per capita withdrawal quadrupled.

Between 2000 and 2050, the world’s population is expected to increase byabout 3.3 billion people and therefore greatly increase the demand forwater. (Data from World Commission on Water Use in the 21st Centruy)

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How Do We Use the World’s Fresh Water?


Uses of withdraw water vary from one region to another, and from one coutry to another.

Worldwide, about 69% of all water withdraw each year from rivers, lakes, and aquifers is used to irrigate 17% of the world’s cropland and produce about 40%of the world’s food

Industry uses about 23% of the water withdraw each year, and cities and residences use the remaining 8%

Source: United States Geological Survey. Estimated Use of Water in the United States in 2000.

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It is important to distinguish between water withdrawal and water consumption. Water withdrawal represents the total water taken from a source while water

consumption represents the amount of that water withdrawal that is not returned to the source, generally lost to evaporation

Source: United States Geological Survey. Estimated Use of Water in the United States in 2000.

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Source Freshwater withdrawal in agriculture, industry and domestic use. The agricultural sector is by far the biggest user of freshwater, primarily for irrigation land. This graphic shows the relative percentages of water use by the agricultural, industrial and domestic sectors in the countries of the world in 2000.

Percentage of Total Renewable Water Resources Withdrawn by Region (1998-2002)

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and Solutions.

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What causes Freshwater Shortages?According to Swedish Hydrologist Malin Falkenmark, there are four causes of water scarcity:

1. Dry Climate:

)Solutions.

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What causes Freshwater Shortages?

2. Drought: is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation and evaporation is lowerthan normal. It can have a substantial impact on the ecosystem and agriculture of the affected region

)Solutions.

This view of Alabama's Lake Martin on Aug. 27 shows how low water levels have fallen.

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)Solutions.

Desiccation cracks produced by drying out of a layer of mud

What causes Freshwater Shortages?

3. Desiccation: Desiccation is the state of extreme dryness, or the process of extreme drying.

4. Water Stress: Low per capita availability of water caused by increasing numbers of peple relying on limited runoff levels

Since 1970, water stress and scarcity, intensified by prolongued drought, has killed more than 24,000 people per year and create millions of environmental refugees

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)Solutions.

Since 1970, There are several ways to increase the supplies of fresh water in a particular area:

• Build Dams and reservoirs to store runoff release as needed.• Withdraw groundwater and convert salt to fresh water (desalination).• Reduce water waste and import food to reduce water use in growing food. Ex: 1 metric ton of grain = 1000 metric tons of water needed to produce the grain.In developed Countries, people tend to live where the climate is favorable and then bring in water from another watershed.In developing Countries, most people (especially the rural poor) must settle where the water is and try to capture the precipitation the need.

Poverty is the principal cause of lack of access to sufficient water, regardless of much water is available

How Can We Increase Freshwater Supplies?

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)Solutions.

Large dams and reservours have benefits and drawbacks.Their main purpose is to capture and store runoff and release it as needed for controlling floods, producing hydroelectric power, and supplying water for irrigation and for towns and cities.Some good news is that the wold’s dams have increased the annual reliable runoff available for human use by neaarly one-third.Some bad news is that a series of dams on a river, especially in arid areas, can reduce downstream flow a trickle and prevent it from reaching the sea as a part of the hydrologic cycle

What are the Advantages and Disadvantages of Large Dams and Reservoirs?Dumps and Reservoirs:

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)Solutions.

Desalination involves removing dissolved salts from ocean water. It is another way to increase supplies of fresh water

How useful Is Desalination:

Method for desalinating water is:

1. Distillation: It involves heating salt water until it evaporates (and leave behind salts in solid form) and condenses as fresh water

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)Solutions.


Method for desalinating water

2. Reverse osmosis: It involves pumping salt water at high preassure through a thin membrane whose pores allow water molecules, but not dissolved salts, to pass through. In effect, high pressure is used to push fresh water out of salt water

1. Water flows in from the estuary or sea 2. Salt water contains sodium and chloride ions 3. Pressure is applied to force salt water through

membrane 4. Semi-permeable membrane with millions of

microscopic holes 5. Clean water fit for drinking 6. Saline concentrate flows out

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)Solutions.

Disadvantages:1. Fisrt, it is expensive because it takes large amounts of energy.

Desalinating water cost 2-3 two three times as much as the conventional purification of fresh water

2. Second, desalination produces large quantities of wastewater (brine) containing high levels of salt and other minerals.

3. Third, Dumping the concentrated brine into the ocean near the plants increases the salinity of nearby ocean water and threatens food resources and aquatic life in estuary waters. Dumping it inland could contaminate groundwater and surface water.


Future:Scientists are working to develop a new membranes for reverse osmosis

that can separate water from salt more efficiently and under less pressure.

However desalinated water probably will not be cheap enough to irrigate convencional crops or meet much of the world’s demand for fresh water.

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)Solutions.

For decades, the U.S. and other countries have been experiment with seeding cloud with tiny particles of chemical. The particles form water condensation nuclei and thus produce more rain over dry region and more snow over mountains.

The bad news is that is not useful in very dry areas, where it is most needed, because rain clouds rarely are available there, and introduces chemical particles into soil and water system, harming people, wildlife and agriculteure productivity.

By other hand, some analysts have proposed towing huge iceberg to arid coastal areas and pumping fresh water from the melting bergs ashore. But this technology is not available yet and the cost is too high

Can cloud Seeding and towing Icebergs Improve Water Supplies?

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and Solutions.

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)Solutions

Heavy rain or rapid melting of snow is the major cause of natural flooding by strems. This causes water in a stream to overflow its normal channel and flood the adjacent area, called floodplain

What are the causes and effects of flooding?

Floodplaints, wich includes highly productive wetlandss, are an important part of the earth’s nature. They provide natural flood and erosion control, maintain high water quality, and recharge groundwater.

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)Solutions

Floods are natural phenomenon with several benefits:1) Provide the world’s most productive farmland2) Recharge groundwater and help refill wetlands3) Soil more fertile and provide nutrients in which it is

deficient


The bad news is that each year floods kill thousands of people and couse tens of billions of dollar in property damage.

U.S. 59 flooding in Houston from Allison (2001)

Flooded I-10/I-610/West End Blvd. Interchange and surrounding area of northwest New Orleans from Hurricane Katrina.

flooding in Alicante (Spain)

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)Solutions

Floods like droughts are consider natural disaster, but since 1960s human activities have contributed to the sharp rise in flood deaths and damages increasing the severity of flood damage in several ways:


i) One is removal of water-absorbing vegetation

ii) Draining wetlands that absorb the floodwaters and reduce the severity of flooding.

iii) Living on floodplaintsiv) Pave or Build, replacing

waterabsorbing vegetation, soil, and wetlands with highway, parkings… etc.

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)Solutions

Make channelization, It can reduce upstream flooding, but it removes vegetation and increases stream velocity

Build leeves that contains and speed up stream flow, but this increases the water’s capacity for doing damage donwstream.

How Can We Reduce Flood Risks?

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)Solutions

Building Dums can also reduce the threat of flooding. A flood control dam built across a stream can reduce flooding by storing water in a reservoir and releasing it gradually.

How Can We Reduce Flood Risks?

Hoover damThree Gorges Dam

•Water pollution is any chemical, biological or physical change in water quality that has a harmful effect on living organisms or that makes water unsuitable for desired uses.

•Water pollution is related to air pollution, land-use practices, climate change, energy use, solid and hazardous waste and density of people, farms and industries producing sewage and other wastes

• Point sources: discharge pollutants at specific locations through drain pipes, ditches, or sewer lines (factories, sewage treatment plants, mines, oil tankers…)

• Nonpoint sources: are scattered and diffuse and cannot be placed to any single site of discharge (acid and chemicals deposition into surface water from croplanda, forests, urban streets, parking lots…)

• Agricultural activities:Are the leading cause of water pollution. Sediment eroded from

agricultural lands, fertilizers, pesticides, bacterias from livestock and food processing wastes, excess salt from irrigated soils.

• Industrial facilities

• Mining

• One of every five people in the world lack acces to safe drinking water

• 95% of the people in developed countries and 74% in developing countries have access to clean drinking water

•About 1.4 billion people in developing countries do not have access to clean drinking water. 9,300 people die prematurely from infectious diseases due to contaminated or lack of water

• Rivers can recover from moderate levels of degradable, oxygen-demanding wastes and excess heat by dilution and biodegradation of wastes by bacteria only if the flow is not low

• Oxygen sag curve

• In developed countries stream pollution is controlled by laws. Point-source pollution is being reduced, but nonpoint sources are a problem more difficult to solve.

• Examples of succesful cleanup are Thames River in London (1950s) and Ohio´s Cuyahoga River (1970s)

• In developing countries stream pollution is still a growing problem, because of the weak laws and the high cost of building waste treatment plants

• Lakes are more vulnerable to pollution because of the lower flow and water is not mixed (vertical lying).

• Eutrophication: natural nutrient enrichment of lakes

• Cultural eutrophication: Excessive input of nutrients. Near urban or agricultural areas.

• To prevent cultural eutrophication: • Waste tratment systems• Cleaning up the lake (removing excess weed, controlling plant growing and pumping air through lakes)

• A lake can recover its previous state if pollution is stopped. As example we have Lake Washington

• Sources

• The most important problem with groundwater is that it can pollute drinking water

• Groundwater cannot clean itself because it has :

• Really slow flow,

• Low concentration of dissolved oxygen

• Smaller population of decomposing bacteria.

• The cold temperatures slow down the chemical reactions that decompose wastes

•In global scale we don´t know so much about groundwater pollution, but it´s really serious in some areas.

•Underground tanks are expected to pollute groundwater and become a big problem

•Cleaning polluted groundwater it´s really difficult and expensive

•Groundwater can be contaminated with fluoride, nitrate ions, arsenic

•People in China or India are drinking polluted groundwater, which cause big health problems

• Prevention is the most effective and affordable way to protect groundwater from pollutants

• Oceans can disperse and break down large quantities of degradable pollutants if they are not overloaded.

• Coastal areas: Pollution of coastal waters near heavily populated areas is a serious problem

• In many countries is still legal dump dredge spoils

• Also sewage sludge is thrown to the ocean

• Since 1992, countries such as the US has banned these practices

• These laws are difficult to keep and often they are violated

• Sinking of oil tanker like the Exxon Valdez or Prestige

• Day to day activities such as washing oil tankers, lakind and unloading oil tankers at ports, leaks from oil pipelines, refineries and storege tanks.

• Almost half of the oil that reaches the ocean comes from activities on land

•To clean up oil spills we have several methods:• Mechanical methods : Floating booms, skimmer boats and absorbent devices• Chemical methods: coagulating agents,dispersing agents• Fire • Biological methods

• These methods can recover no more than 15% of the oil, that´s why preventing oil pollution is the most effective solution

• One step to prevention is to construct oil tankers with two hulls, but in 2004 half of the world´s oil tankers still had the older single hulls.

• Most of these effects disappear within 3-15 years• Depend on:

• Type of oil• Type of aquatic system• Amount • Distance of release from shore• Time of year• Weather conditions• Average water temperature• Ocean currents

• From sewage treatment we obtain sludge, which:

• 9% is placed in circular digesters to let bacteria produce compost• 36% is used as biosolids, fertilizers.• 55% is dumped in landfills, where it can contaminate, or incinerated, which

can pollute the air.

• Using the sludge to fertilize crops can be dangerous for the health, because of the bacteria, toxic metals, chemicals…

• It is necessary to stablish laws to control the use of sludge as fertilizer.

Solutions to avoid the presence of chemicals and toxic substances in sludge are:• Require industries and businesses to remove toxics from water sent to

sewage treatment plants• Require industries to reduce toxic chemicals use

• Another solution to treat sewage are the living maquines. They use natural and artificil wetlands to treat sewage in a low-tech, low-cost way.

• We have also wastewater gardens

• Bioreactors have a genetically modified bacteria which consume pesticides

•Miller, G.T.: Living in the Environment. Brooks/Cole, Thomson Learning. 2005

•[4] Miller, G.T.: Environmental Science. Brooks/Cole, Thomson Learning. 2004

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