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Water for WorkEducator's NotesWater is a basic necessity of life. Water contributes not only to our survival, but also to the quality of our lives. Human beings have harnessed water to improve their lives since the dawn of time. In some ways, the history of civilization is the story of how we have made water work for us in increasingly ingenious ways. As early as 5000 BC, our predecessors used irrigation to increase crop production. Archaeologists have found masonry sewers dating back to 2750 BC and amazingly, water-flushed toilets have been found, dating back almost as far! Water played and continues to play a special role in the growth of our nation. The first residents of the Atlantic Coast the Mi'kmaq, Maliseet and Beothuk people relied heavily on inland waterways to travel through the dense forests of what are now the Atlantic Provinces. The fur trade, which stimulated the exploration of Canada's vast interior, was totally dependent on water for transportation. Water powered the many mills that dotted the waterways of the Maritimes and Upper Canada, enabling the production and export of grain and lumber (among other products), two early economic staples. As Canadian industry diversified, water was put to new uses: as a coolant, a solvent, a dispersant, and as a source of hydroelectric energy. Transportation of goods by water is still an efficient way to move bulk goods. Water is also the basis of cheap energy. Water is a raw material in the manufacture of chemicals, drugs, beverages, and hundreds of other products. It is an essential part of manufacturing processes that end in every kind of good: from airplanes to zippers. In other words, we depend on water for most of our technology, comforts and conveniences, and, or course, for personal hygiene and to flush away our waste. Many people think that it really makes no difference how much water we use, or what we use it for. Actually, the way we use water is very important. Some uses, for example, are incompatible with others. Some uses remove water from the natural cycle for longer periods than do others. Worst of all, most industrial water uses may actually lower the quality of the water. Much of the water in North America has been developed. In less than 100 years, we have developed thousands of huge lakes; some more than a hundred miles long; and have created more than 500 000 smaller lakes and ponds. We turn rivers into staircases for ships and we live in what some ecological writers call the "Age of Dams"1. Hydro-Québec's La Grande River power plant, completed in 1982, is the world's largest underground generating station. Three great rivers; the Eastmain, Opinaca, and the Caniapiscau; were diverted to feed the 500-mile-long La Grande project, doubling the mean annual flow of the La Grande River and increasing its winter flow by a factor of eight. In the resulting trade-off the Eastmain was reduced to little more than a stream, and over 6 000 square miles were flooded. Political leaders see such hydro-power projects as economic miracles, creating jobs, power-for-sale and a vast network of economic spin-offs. Environmentalists argue that such projects are ecologically devastating, and, in 1992, equated the damage to be caused by the proposed James Bay Hydroelectric Project to be on par with the destruction of the Amazon rain forest. Quebec is not the only Canadian province seeking to develop its water resources. Manitoba has dams, diversions and altered flows on the Churchill and Nelson Rivers; Ontario has considered the re-development of Hudson Bay-bound rivers. Consider the impact of such development on the Hudson Bay region. How will it affect the ecological flux of the bays, the arctic char, the beluga whale, the bearded seal, the Canada goose, the Cree, the Inuit, even the fishermen of Newfoundland? What we do affects our neighbours locally and globally. Water quality should be of great concern to all water users that is, to everyone in the world. Ultimately, we all draw from the same supply of water. Most Canadians live downstream from somebody else. Even if they don't, everyone in the world and everyone through the ages has drawn from the same basic supply of water. This basic supply has been used billions of times and is replenished continually through the hydrologic cycle. People are only now becoming aware of the real limits to the use of water, and are more conscious of when and where it is returned to nature, particularly if it is returned diminished in quality and/or quantity. We must learn to understand water use where we use water, what to measure, what the main uses of water how, how our main uses compete and interfere with each other, and how to manage the growing competition for water resources. Where We Use WaterThe most obvious and immediate uses of water occur in its natural setting. These are referred to as instream uses. Fish live in water, and some birds and animals require aquatic habitat to survive. These are examples of non-human instream uses. Hydroelectric power generation, shipping and water-based recreation are examples of human instream uses. Instream uses are not always harmless. For example, oil leaking from boat motors and freighters causes pollution. The large reservoirs required by hydroelectric power generating stations remove water by evaporation and completely change the river regime for downstream users. The greatest number and variety of water uses occur on the land. These are called withdrawal uses. This terms is appropriate because the water is withdrawn from its source (a river, lake or groundwater supply), and is piped or channelled to different locations and users before it is collected again and returned to water source. Household and industrial uses, thermal and nuclear power generation, irrigation and livestock watering all fall into this category. Most withdrawal uses "consume" some of the water, meaning less is returned to the source than was taken out. Furthermore, the water which is put back into its natural setting is often degraded. For example: water leaving our houses contains human and household wastes. The same is true of water used in many industrial processes. Often this liquid waste is only partially treated, if at all, before it is returned to nature. A Brief Examination of Five Occurrences of Withdrawal UseThermal Power Generation Why is so much cooling water necessary? Because today's thermal energy production processes can only convert about 40% of the fuel's energy into useable electricity. The rest of the fuel's energy is wasted. This is a doubly inefficient process, in that firstly, about 60% of the energy from the fuel is wasted and secondly, the water required to cool the heat (to a temperature where it can be safely released into the environment) is itself wasted. This cooling requires a continuous flow of water to circulate through the condenser. All the cooling water is returned to the environment much warmer that its original temperature. Evidence of this warmed water can be found in the cooling ponds located on the grounds of most thermal powered generating stations (there's one located in Trenton, Pictou County). Manufacturing Municipal Use Agriculture Mining Water is also used to extract and process oil that cannot be recovered by conventional drilling methods. Deep well injection, for example, involves pumping water into wells under pressure to force the oil to the surface. Although the mining industry had a gross use almost as great as agriculture, mining accounted for only mining accounted for only 1% of all water withdrawals in 1996. This was the smallest withdrawal use, but mining recirculates its water intake to a greater extent than any other sector. A Brief Examination of Six Instream Water UsesInstream uses cannot be measured in terms of quality because the water used is not removed from its natural environment. Instead, instream uses are described by certain characteristics of the water or by the benefits they provide to us and the ecosystem. Flow rates and water levels are very important factors for instream water users. When these conditions are changed by a dam, for instance, it is easy for conflicts between users to arise. The most common conflict that arises between instream users is between hydroelectric developers and other users (with respect to aquatic life, wildlife, water supply and water transportation). Storage of the spring freshet3 removes the natural variability of streamflows. The life processes of aquatic species may depend on this variability, in particular, the highly productive ecosystems of deltas, estuaries and wetlands. To make the best use of our water, all needs must be carefully assessed and considered. Hydroelectric Power Generation Water Transport Freshwater Fisheries Wildlife Recreation Waste Disposal ActivitiesWind and WaterGrades 4, 5, 6 Science PurposeA windmill uses the force of the wind to do useful work. Water wheels turn the energy of running water into useful power. Before the first steam engines were invented, windmills and water wheels were almost the only machines that were not powered by human or animal muscles. Farmers often used them to grind corn and pump water. When engines fuelled by coal and oil came along, windmills and water wheels began to disappear. However, they are becoming popular once more. Today, we are more aware of the pollution caused by burning fossil fuels such as coal and petroleum. Wind and water power are clean and quiet sources of energy. Water wheels can be built wherever there is fast-flowing water that will turn the blades of the wheel. Most modern water wheels are complicated machines that are used to make electricity. They are called hydroelectric turbines, and the electricity they produce is hydroelectricity. Hydroelectric turbines are usually built along big rivers or in dams, where water is forced to pass through a turbine in order to get out of the reservoir. Electricity can even be generated in coastal areas, by the movement of the tides through a turbine. Materials
ProcedureCreate the turbine Create the turbine assembly Create the sluice Place the bottle in the dish. Fit the tube (with the funnel attached) into the neck of the bottle, making sure that the stream of water will hit the plastic blades of the wheel (hold the funnel at a higher level than the bottle neck opening so that the water will run downhill). In a hydroelectric power station, water falling down a pipe (the plastic tubing) from a dam (the funnel) spins the blades of the turbine (the water wheel). The turbine drives a generator that makes electricity. Predict the results of a change in the rate of flow Lift a Load with WaterGrades 4, 5, 6 Science PurposeUsing water to lift a heavy weight is known as hydraulic lifting. Very powerful machines allow workers to pull, press or lift things that they wouldn't ordinarily be able to. Hydraulics greatly increase the force produced by these machines. In hydraulic machines (like earth movers), pipes carry a liquid from a pump to cylinders where the liquid pushes out pistons with great force. In an earth mover, pistons drive the earth moving shovel into the ground and let the machine raise a heavy load of soil. The mechanics of this hydraulic movement are demonstrated in this activity. When the funnel is raised above the level of the book, and weight of the water in the tube pushes water into the balloon. The swelling balloon then exerts enough pressure to push the heavy book upwards. Materials
ProcedureFit the neck of the balloon over the end of the tube and seal the joint tightly with tape. Cut the top off the bottle, making a hole in the side, near the base of the bottle. Push the balloon through the hole in the side of the bottle, so that the plastic tube is sticking out through the side. Tape the funnel firmly to the "free" end of the tube. Place the can inside the bottle, on top of the balloon. The sides of the bottle should extend just past the top of the can. Lay the heavy book on top of the bottle. Lift the funnel so that it is raised about six inches or more above the upper rim of the bottle. Pour some water into the funnel, so that it runs down the tube and into the balloon. As the balloon swells, the can on top of the balloon is raised, and so is the book! Make It Sink Then Float!Grades 4, 5, 6 Science PurposeA huge ship floats on water, even though it is very heavy. Yet a small, light object such as a marble will sink. Why? The weight of objects alone does not suggest whether or not something will sink or float. Whether or not something will float depends on how much water it displaces, or pushes aside. Have you ever noticed the marks painted low on the hulls of ships? These marks show safe loading levels. An overloaded ship settles too low in the water, and risks sinking. Materials
ProcedureDrop marbles into the water. Notice that they quickly sink to the bottom of the container. Ask the students to predict what will happen if the clay is dropped into the container. Roll the clay into a ball, and drop it in. The clay will also sink. Just like the marbles, it does not displace much water. Remove the marbles and the clay ball. Shape the clay to make a flat-bottomed boat (or a plate-like form). Float the clay in the container of water. This new shape displaces more water than the ball form did: more water has been displaces, and it pushes with more force, supporting the clay boat, making it float. Add the marbles to the clay boat they are its "cargo". The boat will settle lower in the water, but displaces more water and still floats. Notes:
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