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WATER MANAGEMENT
Definitions of Water
- Water is a clear liquid, without colour or taste, that falls from the sky as rain and is necessary for animal and plant life.
- Water is a colourless, transparent, odourless liquid that forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms.
- Water is the liquid that descends from the clouds as rain, forms streams, lakes, and seas.
- Water is a transparent, odorless, tasteless liquid, a compound of hydrogen and oxygen.
- Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of most living organisms.
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| Water |
Definitions of Water Management
- Water management is the activity of planning, developing, distributing and optimum use of water resources under defined water polices and regulations.
- Water management is the management of water resources for the coming generations.
- Water management is the activity of planning, developing, distributing and managing the optimum use of water resources.
- Water management is the control and movement of water resources to minimize damage to life and property and to maximize efficient beneficial use.
Management of water includes treatment of drinking water, industrial water, sewage or wastewater, management of water resources, management of flood protection, management of irrigation, and management of the water table.
Water is a basic necessity. No living creature can live without water. There’s a scarcity of water. To avoid this scarcity, water is saved and managed efficiently.
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| Water management |
Economic Uses and Importance of Water
1. Water is used for domestic purposes
2. Water is used for agriculture development [irrigation]
3. Water is used as a source of hydro-electric power
4. Water is used for industrial development
5. Water encourages the development of the fishing industry
6. It encourages the development of the tourist industry Water is used for navigation i.e. it stimulates the development of transport and communication
7. Water influences weather activities i.e. rain formation
Relationship between Family Size, Water Supply and Quality of Life
There is a very close relationship between quality of life and water. An adequate and reliable water supply greatly improves the quality life of people. This is because they do not have to spend most of their time, income and effort searching for water.
Availability of water means that family members are easily able to cook, clean themselves and do other family chores.
Also the family size determines how much water is needed at a given time and how frequently available it should be. The larger the family the larger the amount of water, the smaller the family the lower consumption of water.
Where the water is not piped and frequently supplied for example in rural areas, family members especially girls and women spend most of their time and effort looking for water. In some other communities, girls are not allowed to go to school since they are required to fetch water and ensure that it is available for the whole family.
In case of a smaller family, they are able to use stored water over a long period in case the frequency of water supply is low. Therefore, under conditions of low water supply, a small family is more likely to experience water shortage problem than a large family.
Relationship between Vegetation and water supply
Vegetation play a very crucial role in ensuring a continuous water
supply. Presence of places with dense forests and other forms of vegetation act as water catchments. This means that they retain water by preventing it from easily washing away or rapidly evaporating.
Places with abundant vegetation therefore have higher chances of experiencing a reliable water supply than places that have little or no vegetation. Indeed, the lack of vegetation may lead to desertification and consequently very little or no water availability. It is also important to note that vegetation cannot exist if there is lack of water. Even desert vegetation requires water, though in small amounts for it to exist. The more available water is the denser and healthier the vegetation will be. Where there is little water available the vegetation is sparse. Vegetation and water supply are therefore highly related and dependent on each other.
How long distance to water sources affects the girl child
In rural areas, family members especially girls and women spend most of their time looking for water. In Tanzania, most rural communities the task of fetching water is placed on women and girls. It is the girls who have to do this as the women are engaged in other domestic duties or family chores such as taking care of babies and cooking. The distance between the home and the water source affects the girl child in the following ways;-
1. When the distance is long, it means that the girls have to walk the long distance to fetch the water. By walking the long distance they get tired, they may get attacked/molested along the way and in some cases, there is a little time left for activity such as learning or playing. For those who are lucky to go to school, they tend to be too tired to pay much attention in class hence, poor performance. But for those who are not lucky enough to go to school are condemned illiteracy. All of these may turn into early marriages or teenage pregnancies and some of them tend to experience psychological problems in their childhood as well as in their adulthood due to lack of time to play, robs them of a happy and balance childhood.
2. On the other hand, if the distance from the home to the water source is short, then the girls spend less time in fetching water and hence they have more time to play and to go to school, thus they will be able to pay attention in the class and do well in their studies.
3. In addition, children who are consistently exposed to hazardous, un portable water or exposed to pumps or water source that have been contaminated by water-bone bacteria, contracting diseases such as cholera and they are often affected by life threatening diarrhea from parasites in unclean water.
Problems Caused by Water
1. Water causes floods
2. Water provides habitat of dangerous animals
3. Polluted water is a source of water born diseases
4. Flowing water causes soil erosion
5. Large water bodies may cause barrier for communication.
RIVER BASIN DEVELOPMENT RUFIJI BASIN DEVELOPMENT AUTHORITY
Rubada, Tanzania
It was authorized by the government of Tanzania in 1975 to plan and coordinate the development activities in the Rufiji River. Rufiji river has two main tributaries:- Great Ruaha Kilombero River It is situated in Iringa but there are other centers which are located close to the basin Boarders i.e. Dar es salaam Morogoro Mbeya Songea Dodoma
Benefits of RUBADA
1. Hydro power plants. Twenty two major hydro power sites have been identified in the Rufiji basin of kidatu, Mtera, Mpanga, Ruhudji, Mnyera and Iringa Lukose.It generate electricity which is used within the immediate area in other parts of the country.
2. Agriculture A large number of irrigation projects have taken place in the basin (Improvement of Agriculture production due to irrigation). i.e. Sugarcane, growing rice in the kilombero and usangu plains.
3. Forestry 10% of the total basin is covered by forests which are important for regulation of water resources.
4. Industrial development Due to the availability of power, industrial activities have advanced in the region hence increase the volume of trade in the country.
5. Tourism Rufiji basin is one of the major tourist attraction in Tanzania i.e. Selous game reserve, Rungwe and Usangu game reserve as well as Mikumi and Ruaha and National parks which are tourist attractions, are located within the basin.
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| River Basin Development |
Problems Faced by RUBADA
1. Lack of enough capital to invest in the area Infrastructure is poorly developed.
2. Lack of qualified personnel Low level of technology Fluctuation of water levels Lack of support by local communities
Importance of Rivers, Dams and Lakes
1. Helps in generating HEP
2. Promote transport and communication
3. They supply water for irrigation and domestic uses and industrial activities
4. They modify the environment like introducing moisture to the atmosphere which later leads to the formation of rainfall
5. They attract settlement
6. Features like waterfalls attract tourists
7. They promote fishing industries
Problems of Rivers, Dams and Lakes
1. Fluctuation of volume of water
2. May lead to spread of diseases like bilharzia etc
3. Flooding of rivers may lead to destruction of properties
4. The invasion of vegetation in these water bodies lead to problems in fishing and navigation.
TENNESSEE RIVER VALLEY AUTHORITY (TVA)
Tennessee river valley is found in the U.S.A and is a tributary of Ohio river. The government of U.S.A organized the development of the valley with the general aim of solving economic difficulties of the people.
Benefits of the Tenessee Valley Authority (TVA)
1. There has been an increase in water supply for irrigation, domestic use and industrial use.
2. Navigation in the Tennessee River has improved such as the commercial freight ships operating in the river.
3. Hydroelectric power was made available to many people.
4. The floods have highly been controlled.
5. The project has created job opportunities for many people.
6. Increase on the size of arable land due to soil control.
7. Fishing industry has developed due to the construction of dams.
8. Provision of hydroelectric power has led to the development of different manufacturing and heavy industries.
Problems Facing Tennessee River Valley
1. Soil erosion can also affect the established Tennessee River Valley project.
2. Soil exhaustion due to intensive farming hence poor farming and low yield.
3. Water pollution especially by the industries discourages the utilization of water from the river basins for economic development.
4. Accumulation of silt in the dams leads to the reduction of the volume of water.
5. The outbreak of diseases like cholera due to accumulation of water.
6. Unreliable rainfall and excessive evaporation lead to the drying of the river and other water bodies hence economic activities cannot take place easily due to the dryness.
Prospects of the Tennessee River Valley
1. Constructing more dams for retaining water all year round
2. Maintaining the roads and modifying them to better standards
3. Training the local people on other economic activities like navigation fishing and not to rely on one activity to solve the economic problems of the people
LAND RECLAMATION
The recovering of land that has been rendered unsuitable for use to make it usable again. Or Is the process of turning the poor land into a useful state through the improvement practices for economic and social development.
Aims of Land Reclamation
1. To increase the size of land available for agriculture purposes. This was carried out in the Tennessee valley. Previously unused land was irrigated in order to increase crop production.
2. To increase the size of land available for human settlement. This may become necessary if the population of an area grows beyond the land is available. It may also create land to resettle people who are being moved from another area.
3. To make available more land for the establishment of industries and offices.
4. To be in proximity to resources in order to be able to gainfully utilize them.
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| Land Reclamation |
Factors Which may Cause Land to become Unusable
1. Land may be damaged due to natural hazards like fire
2. Human activities can also damage the land i.e. poor farming methods, mining and pollution.
3. Cares of water logged land for example swamps and marshes
Methods of Reclaiming the Land / Land reclamation Techniques
1. A forestation or reforestation [planting trees]
2. Tsetse fly control which is done by clearing, spraying the area in order to kill them
3. Irrigation which is practiced where the natural precipitation is not sufficient to meet the crop moisture requirements
4. Draining water using canals and pumps can reclaim or constructing embankment for water logged land /marshy areas or wetlands
5. Planting reeds so as to allow water absorption by plants so as to dry the areas for cultivation.
6. Planting grass cover to check erosion
7. Burning reeds so as to clear the area for cultivation and settlement
Purposes of Reclaiming the Land
1. To increase availability of arable land for cultivation.
2. To expand carrying capacity of land. This means that the land can be used for industrial areas as well as residential areas.
3. For road and railway construction.
4. To control floods caused by water from the sea. The best example of land reclamation in the world is the Zuider Zee land reclamation scheme in Holland (Netherlands).
LAND RECLAMATION IN NETHERLANDS
Netherlands lies between the North Sea [north] and Belgium [south], Netherlands means low lands, it was covered by flood water from the sea, in one part were marshes, swamp land or land covered with poor soil. Netherland occupies an area of 40844 square km. the land in the northern parts of the country have been reclaimed from the sea and made arable. An area of reclaimed land is called POLDER. A project drawn by a Dutch engineer called CORNELIS LELLY.
Aims of Land Reclamation in Netherlands
1. To increase dry land for residential and industrial development
2. To reduce the danger of over flooding and obtain land for agriculture and livestock keeping activities e.g. in 1953, 1800 people died due to the rise of sea level.
Steps of Land Reclamation taken in Netherlands
1. Dykes / embankments were built to enclose part of the sea water. The sand was imported from Germany and Sweden
2. Water was pumped out of these areas using wind mill and electrical pumps
3. The dry land was planted with reeds to control weeds and preserve moisture in the soil and to absorb more salt from the soil.
UNDERGROUND WATER
Underground water is the water found in the ground. It water also called ground water or subterranean water. The true underground water is held in the ground in the zone of water saturation called aquifer or phreatic zone. It occupys interstices (pores) or voids of pervious rocks and soil. Like surface water, it is derived principally from precipitation that falls upon the earth’s surface and percolates downward under gravity.
Types of Underground Water
The Underground water is categorised based on its source as follows:
1. Connate water: It may also be described as fossil water. This is water trapped in the pores of the rock during the formation of the rock. Connate water can change in composition thought the history of the rock. Connate water is normally saline. Formation water or interstitial water, in contrast, is simply water found in the pore spaces of rock and might not have been present when the rock was formed. This type of water can be found in desert rocks where rainfall does not occur for a long period of time. Connate water generally plays an insignificant role in ground water studies. Agroforestry as practised in Shinyanga region
2. Meteoric water: This refers to underground water which originates from rainfall and other forms of precipitation such as hailstorms and snowfall. When the rainfalls or snow melts, a considerable portion of this water gradually infiltrates into the ground. This infiltrating water continues its downward journey to the zone of saturation to become part of the ground water in aquifers (water-bearing rocks).
3. Juvenile water: Juvenile water, also described as magnetic water, is water that exists within magma. It is brought close to the earth during vulcanicity. Magnetic water rises from great depth accompanying the magma flow from down the earth’s crust.
4. Oceanic water: This is underground water that results from the seepage of ocean water into the ground. It is common in coastal areas where ocean water seeps horizontally into the ground from the ocean.
Tapping Underground Water
Underground water can be tapped and put into various uses. The water tapped from the ground can be used for domestic and industrial purposes. Domestic uses include cooking, washing, bathing, watering plants, cleaning and many other uses. Industrial uses may include cooling of machinery, dissolution and dilution of chemicals, beverage manufacture, etc.
Underground water can be tapped in a number of ways which include the following:
1. Drilling boreholes: These are holes dug deep into the ground to reach the water table. When the water table or underground water is reached, the water seeps up through the hole under pressure. It is then brought above the ground by pumping manually or using a water pump.
2. Digging wells: Just like boreholes, a hole is dug into the ground until water is reached. The difference between boreholes and wells is that water from the well is mainly drawn mechanically using containers such as buckets that are raised mechanically or by use of simple pulleys or hand. The walls of wells may be lined with bricks or stones and cement.
3. Where the water occurs very close to the surface, the soil may be scooped to expose the water. The water may then be scooped using cups or other containers. It may be directed to farms for irrigation via channels or trenches. The water may also be pumped and channelled into pipes to provide tap water.
4. Underground water may be naturally exposed to form springs or oases in deserts. This water may be scooped directly using containers. It may also be directed to farms through channels.
The Resources that can be Extracted from Water
There are a number of resources that can be obtained from water. Outlined below are some of the resources that can be extracted from water:
1. Fish and other edible creatures, such as crabs and prawns: These resources may be caught either for sale or family consumption.
2. Building materials: The building materials obtained from water include sand, coral rock, gravel and clay. Sand can be obtained from beaches of seas or lakes or river valleys and rocks are collected from the sea shore. The rocks and gravel are a result of erosion of the coastal rock by sea waves. Clay can also be obtained from the sea floor or river bed.
3. Electricity: Marine wind is used to turn windmills to generate electricity. Hydroelectric power is also a resource from the water since it results from the running water which is used to turn turbines to generate electricity.
4. Saltwhich is used at home and in industries, is mainly obtained from sea water though it can also be extracted from salty rivers and lakes.Brick-lined well
5. Ornamental items such as cowrie shells, snail shells, lobster shells, etc are also water resourcessince they come from animals that inhabit water.
6. Sea weed is used in many maritime countries as a source of food, for industrial applications and as a fertiliser. High utilisation of these plants as food is in Asia, particularly Japan, Korea andChina, where sea weeds cultivation has become a major industry.
7. Limestone and gypsum: Limestone forms from shells of dead marine organisms ranging from molluscs to corals and plants. Limestone can be used directly or converted into cement for construction purposes. Gypsum forms during evaporation of sea water and thus may occur with limestone. The gypsum deposits are mined and generally converted into Plaster of Paris which is mainly used as a building material.
Methods Used for Extracting Resources from Water
The following are the means by which the named resources may be extracted from the water:
1. Fish and other edible marine creatures. Fish may be obtained from water through use of a hook and line, nets, herbs, spears or traps. In the case of a hook and line, bait (such as worm or meat) is attached to a hook which is joined to a stringtied to a long stick or rod. The hook is sunk into the water. When the fish bites the bait, it gets caught by the hook and pulled out. This method is used for small-scale fishing.
2. The use of certain plants called tephrosia. This plant ispoisonous to fish. When the leaves of this pea plant are pound and mixed with water, the fish arepoisoned and they fall unconscious and float on water. They are then picked from the water by hand oruse of a spear (harpooning). The fisherman spears fish in water and it is attached to the tip of the spearfrom which it is detached and put in a container.
3. The traps are mainly used where there are floods or at the coast where there are tides. These traps areset up at the bank of the river or on the beaches. The fish are washed into the banks or beaches by thewater. As the water receded the fish remain trapped behind the traps.
4. Nets are used to catch a large number of fish. With nets the fish are enclosed in a net with smallperforations through which fish cannot penetrate. They are then hurled to the sea shore, removed from the net and put in containers.
5. Sand is extracted from the beaches or dredged from the ocean or river beds. This can be done by using scooping machinery or by hand using shovels, pans, hoes, etc. It is then loaded onto truck or lorryusing shovels or a grab dredge.
6. The process of extraction of salt from water involves evaporation. The salty water is trapped inevaporation ponds. The sun evaporates the water. As the water vapourizes, the salt remains behind.Eventually, enough of the water evaporates to leave behind a layer of salt crystals that can becollected, dried and stored in bags.Another alternative for salt extraction from the water is by means of evaporation tanks. Salty water ispumped into the tanks where the water is evaporated, leaving the salt behind.
The Problems Caused by Extraction of Water Resources
Extraction of water resources may cause various problems and disturbance to ecosystem. Below are some of these problems:
1. Overfishing, and indiscriminate fishing whereby even very young fish are caught reduces theavailability of fish resources in water. It also causes an imbalance in the ecosystem.
2. Water pollution is a problem where dynamites or poisons are used as methods of
fishing.Dynamites produce loud sounds which disturb the fish and other aquatic organisms while poisonkills fish, aquatic plants, and other marine organisms.
3. Sand harvesting may lead to loss of media for growth of plant life. It may also disturb aquatic life,for example, it may interfere with breeding of some marine organisms such as monitor lizards,Salt evaporation ponds, snakes, crocodiles, alligators and turtles. These animals normally lay eggs in the sand. Sand extraction from river banks may also lead to flooding since the sand deposited besides a river acts as a levee which prevents water from leaving its channel during floods. It may also accelerate river erosion because the extraction process loosens the soil and makes it easy to erode.
4. Harnessing hydroelectric power from river water requires dams to be constructed. This can cause water shortage to the areas downstream. Water trickling from the tank to the nearby areas may also lead to flourishing of disease vectors such as mosquitoes and snails which harbour causative agents for malaria and schistosomiasis respectively.
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| Water Pollution |
The Solutions to these Problems include the following:-
1. Giving guidelines on the kind of nets allowed for fishing certain fish species. To achieve this, the fishermen must be closely monitored to ensure that holes of the nets they use for fishing are not too small to catch even young fish.
2. Restricting fishing in some parts of the water, especially those areas identified as fish breeding grounds, so as to allow fish to breed and increase in number.
3. Encouraging and educating people to practice fish farming so as to reduce fishing pressure on natural water bodies such as rivers, lakes and seas.
4. Restricting or controlling sand harvesting in beaches and shores so as to ensure that aquatic environment is not destroyed and that aquatic life is not disturbed.
5. Banning the use of dynamites or poisons in fishing because this act pollutes the water and is likely to harm fish consumers.
6. Taking stern actions against those people breaching environmental conservation laws. The actions may include fines, jail sentences or both. Water pollution Water pollution is the introduction of substances that lower the quality of water bodies such as oceans, rivers, lakes, aquifers and ground water. This makes the water unsafe for use in homes and industries. Water pollution also affects living organisms (plants and animals) living in water.
The Major Causes of Water Pollution
1. Agricultural chemicals; Agricultural chemicals that are applied to crops and animals drip onto the soil and may eventually run off into the local streams and rivers. They can also seep down to reach ground water. These chemicals contaminate the water and make it unwholesome for human use and can drastically affect the aquatic life.
2. Oil spills; Oil spills in oceans and seas cause water pollution and big problems for local wildlife, fishermen and aquatic organisms. Oil spilled onto land is also carried into water bodies by surface run off. This includes drips of oil, fuel and fluid from motor vehicles, oil spilled onto the ground at filling stations; and drips of oil from industrial machinery. These sources and many more combine together to form continual petroleum pollution to all of the world’s waters.
Mining causes pollution in a number of ways:
1. The mining process exposes heavy metals and sulphur compounds that were previously locked deep in the earth. Rain water leaches these compounds out of the exposed earth, resulting in “acid mine drainage” and heavy metal pollution that can continue long after the mining operations have practically ceased.
2. The action of rain water on piles of mining waste (tailings) transfers harmful chemicals to freshwater supplies.
3. In gold mining, cyanide is intentionally poured on piles of mined rock (a leach heap) to chemically extract the gold from the ore. Some of the cyanide ultimately finds its way into nearby water.
4. Huge pools of mining waste slurry (semi-liquid mixture) are often stored behind containment dams. If a dam leaks or bursts, water pollution is likely to take place.
5. Mining companies in developing countries sometimes dump mining waste directly into rivers or other water bodies as a method of disposal.
Other Pollutants which affect the Quality of Water and the Lives of Aquatic Organisms
1. Sediment: The act of clearing the forests to get ample land for agriculture, settlement or wood, leaves the land bare and exposed to the agents of denudation. This accelerates soil erosion and the sediment is free to run into nearby streams, rivers and lakes. The increased amount of sediment running off the land into nearby water bodies seriously affects the fish and other aquatic life. Poor farming practices and cultivation along and close to the rivers, exposes the soil to erosion agents. Soil erosion causes water pollution.
2. Industrial Chemicals: Most of the water that is used in the production process in industries is eventually discharged into water bodies. This waste water may contain harmful chemicals such as acids, alkalis, salts, toxic chemicals, oil, heavy metals and even harmful bacteria, and other reagents. In some cases, the waste water discharged into a water body may be hot enough to kill any organism living in that water.
3. Sewage: In developing countries, about 90% of untreated sewage is discharged directly into rivers and streams. This renders the water unwholesome for domestic and other uses. Untreated sewage harbours a myriad of disease-causing organisms. This is the reason why diseases such as cholera, dysentery, typhoid and bilharzias are very common among African countries. Leaking septic tanks and other sources of sewage can contaminate ground and stream waters as well.
4. Marine debris: (marine litter) Marine debris is trash in the ocean. This is litter that ends up in ocean, seas or other large water bodies. The debris mainly comes from urban sewers and garbage thrown overboard from ships and boats. Examples of marine debris include plastic bags, water bottles, balloons, shoes, lags etc. It can also include items that wash in from the ocean, such as fishing line, ropes, nets and traps, and items from ship such as lost cargo from container ships.
5. Heat: Heat is a water pollutant. Increase in water temperature results in deaths of many aquatic organisms. This is because, as water temperature increases, the amount of oxygen that can dissolve in it also decreases. Therefore, warm and shallow water will contain very little oxygen to an extent that the dissolved gas will not sustain aquatic life. This increase in temperature is most often caused by discharge of cooling water (which is always hot) by factories and power plants. Global warming also contributes significantly to heating of the oceans.
Ways of Conserving Water Resources
Water, as a resource, can be conserved thought the following ways:
1. Avoiding wastage: All people should use water wisely to minimise wastage. All taps should be turned off when they are not used. The used water may be re-used again. For example, water that has been used to rinse clothes can be re-used to mob the floor, soak the dirtiest clothes, rags etc. Do not use water directly from the tap, instead fetch the water in a container and use it wisely.
2. Controlling polluting: People should neither throw wastes carelessly nor introduce any chemicals into water. Stern laws should be made and enforced to stop industries from dumping toxic wastes into the water bodies. Any industry found polluting the water by any means should be heavily punished or even closed down altogether.
3. Protection of water catchment: Vegetation in water catchment areas should be protected and cared for. People should not carry out agricultural activities close to water sources. Planting of trees that consume a lot of water, such as eucalyptus, near water sources or rivers should also be avoided. Any activity that destroys the water catchment should be banned. In the past, the government ordered people to cut down all eucalyptus trees planted close to water sources so as to prevent the water sources from drying up.
4. Education: People should be educated about the importance of conserving the water resources. This education can be conveyed thought mass media and introducing water conservation courses in schools and colleges. The government and other organizations concerned with conservation of water resources should involve local communities so as to get maximum cooperation in their endeavours. The local people must be involved at all levels and should be given freedom to suggest how best these resources can be conserved.
5. Sewage treatment: Sewage is water containing waste matter produced by people. Much industrial sewage contains harmful chemicals and other waste materials. Sewage must be treated before it flows from sewerage systems into lakes, rivers, and other bodies of water. Untreated sewage contaminates the water and, in time, can kill fish and aquatic plants. The sewage makes the water unsafe to drink and can also prevent use of the water for swimming, fishing, and other recreation. Most cities and towns have at least one sewage treatment plant. In most rural areas, homeowners must provide their own sewage treatment. Most do so with large undergroun containers called septic tanks or pit latrines.
6. Controlled use of agrochemicals: Farmers should be educated on the correct use of agrochemicals. Also agricultural activities should not be carried out in areas close to water bodies. The use of organic manures and chemicals in place of harmful industrial chemicals for agricultural production should be emphasised.
7. Recycling of products: People should be advised to recycle the waste instead of dumping it in water sources. This will help reduce the problem of water pollution.
8. Immediate clean up When oil is accidentally spilled in water it should cleaned up immediately before causing any harm to aquatic life or people using that water. This can be done by use of chemicals or special machines called skimmer ships Water Pollution Many resources are extracted from water and used by man.
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