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Water for LifeEducator's Notes"When the well's dry, we know the worth of water" - Benjamin Franklin As we begin a new millennium, our planet faces a critical shortage of clean, fresh water. The problem is not the supply of water – Earth has virtually the same amount today as it did when the dinosaurs roamed the planet.1 The problem is people: our increasing numbers and our abuse of one of our most precious resources. There is no substitute for water. It has already begun to replace oil as a major cause of confrontation in the Middle East. In North America, water rights claims and issues are increasingly in the news. On some level, at least, we are discovering the importance of this vital resource. On average, Canadian residential water use amounts to 335 litres per person per day. This is more than twice as much as the average European, and astronomically more water than people use daily in most developing nations. Except during times of flood or drought, North Americans tend to ignore water. It comes to our taps when called and drains away afterward. Most of us can swim when we want, bathe when we want, water our lawns, wash our cars and allow our children to drink from public fountains. Like good health, we ignore water when we have it. But, like health, when our water is threatened, it's the only thing that matters. When there is no water, there is no life. Most of us can live for almost a month without food, but will die in less than a week without clean, fresh water. Less than one half of one percent of Canadians are without running water, but, in places like Mexico, 15% of the population must haul or carry their water. Water QualityFew things are as insidious as bad water. It's dangerous to your health, but you usually can't tell if you have it. Water can carry some of our most serious diseases – typhoid, dysentery, hepatitis, cholera – and still look clear in the glass. If you pour poison on the ground, even in the driest desert, water will eventually pick it up, molecule by molecule, and, because water is always going somewhere, it will take that poison away. Somewhere. The price Canadians must pay to prevent water-borne disease is constant vigilance against bacterial contamination. Periodic beach closures and local epidemics are evidence that the battle has not yet been won. These problems underscore the need to maintain strict control over water quality and to improve water and wastewater treatment. Of serious concern to us today are the toxic chemicals that enter our water from many different sources, including industry, agriculture and from our own homes. Relatively little is known about the effects of some toxic substances on human health because very often, the effects of toxin ingestion do not become noticeable for long periods of time, and it is difficult to distinguish them from the effects of other factors in our everyday lives (e.g., nutrition, stress, air quality). Much more remains to be done to control toxic chemical pollution. Meanwhile, we can all contribute to the prevention of water pollution by not abusing the water or the land, and by becoming stewards of our own watersheds. Where Does our Drinking Water Come From?When students are asked to answer the question, "where does our usable fresh water come from?" many of them reply in terms of the water they can see: rivers, lakes and streams – surface water (of course, many students will also reply that our usable fresh water comes from the kitchen faucet!). This answer (the former) is partially true. Surface water, precipitation, fog and dew all represent water that is in transit. There is an equally valuable resource of water, however, which usually escapes notice: groundwater. A study of our water supply begins with an examination of rain and snowfall in Nova Scotia. Some precipitation evaporates from the Earth's surface, some soaks into the ground and saturates the soil and rocks below, and some is used by plants. The remaining water runs off the surface of the land, forming a network of streams, rivers and lakes. Whether a particular raindrop becomes surface water or soaks into the ground depends on many factors, including the soil type and moisture; the slope of the ground; and the amount of forest cover, cleared land and/or paved surface present. Surface WaterThe term surface water refers to water stored on the ground in lakes and streams. In Nova Scotia, large areas of exposed or barely covered rock and the effects of glaciation have resulted in the formation of about 6 700 small lakes. These lakes cover about 4% of the province's land mass. Lakes and marshes are most numerous where water cannot penetrate the bedrock easily: on granite, quartz or slate formations. In the southwestern part of Nova Scotia, for example, lakes cover about 11% of the land drained by the Tusket River. In areas dominated by sedimentary rock, there is much less surface water, because water is able to percolate through sedimentary formations. In the River Philip drainage area in Cumberland County (where the geologic formation is mostly sedimentary), less than one percent of the surface is covered by lakes and marshes. The surface of Nova Scotia can be subdivided into "catchment areas" or watersheds. In each watershed area, the water flowing across the surface of the land ends up in a particular lake or stream. Every lake, river and stream in the province is surrounded by its own watershed. GroundwaterUp to 12% of Nova Scotia's annual precipitation soaks down through the soil and loose rock near the surface of the land, filling the pore spaces, fractures and joints within the rock below. Water that is so contained and located below the Earth's surface is referred to as groundwater. Twenty six percent of all Canadians rely on groundwater as their drinking supply. Water is always moving. In order to move, groundwater must be able to flow through the spaces between sand, gravel and rock underground. Two geologic characteristics that affect the movement of groundwater are porosity and permeability. Porosity refers to the amount of water that a material can hold in its pores. A cubic metre of well-sorted gravel will hold 30 to 40% of its volume in water. The same volume of solid granite (without joints or fractures) is impenetrable and will hold water only on its wet surface.2 Permeability is the ability of a material to let water pass through its pores. Every type of soil and rock formation differs in its ability to hold and transmit water. Gravels and sands, or highly porous sedimentary rocks (sandstone or limestone, for example) can usually hold the most groundwater, but even dense rocks like granite or quartzite can hold some water in the joints and fractures that punctuate formations. How water is stored in the soil, and how available it is, depends on the rock type and strata, or the way the earth is layered. By knowing the type of earth materials present and how they are layered, we can estimate, among other tings, how long it will take for a particular contaminant to reach groundwater reservoirs.3 To understand groundwater better, it is useful to follow the course of precipitation moving into the earth. Rain or melting snow makes contact with Earth at the upper layer of soil, or soilwater zone, which may vary in depth from centimetres to many metres. Water enters through every hole or fissure, and thin films spread around soil particles and over the surface of joints. Adhesion also holds water in the very small spaces between the openings, where it either evaporates or is withdrawn by plant systems. The soil water zone is important to agriculture because it furnishes water for plant growth. Only when enough water has completely satisfied the water holding capacity of the soil does water move or percolate downward by the force of gravity. Water may then enter an intermediate zone where variable amounts of the liquid occur in solid openings. Wells drilled into this area will yield no water even though the ground is damp, because the soil particles hold on to their dampness much the same as does a damp towel. During dry periods, capillary action may move the moisture back into the upper layer of soil, where it will be used by plants and organisms living in the soil water zone. The intermediate zone is bordered on its lower limit by a capillary fringe. Soil particles there draw water up from its more dense concentration below through capillary action. If precipitation continues to where water is soaking down through the intermediate zone reaches an area underlain by a less permeable layer, the water will collect where it is stopped by the impermeable rock to form the saturated zone. The upper level of the saturated zone is referred to as the water table. Earth formations within the saturated zone which hold water that can be extracted or withdrawn for use are called aquifers. Aquifers are characterized by their ability to both store and transmit water. The water storage capacity of an aquifer is equal to the total amount of space between the particles and joints in the geologic strata. Aquifers vary in composition from loosely packed, or unconsolidated formations (like those of sand and gravel) to consolidated formations (or sandstone or limestone). Aquifers may be the size of a football field or as large as a small province. Several aquifers may be contained in a single area, separated by a layer of less permeable rock. Geological maps showing cross sections of the Earth's surface may provide clues as to which geologic strata are likely to store water and at what depths. Records of successful wells previously constructed in an area provide further information on local groundwater quantity and quality. Groundwater is constantly moving from areas of high pressure to areas of lower pressure. The direction of groundwater movement within a geologic formation is generally from an elevated ground level toward sea level, under the influence of gravity: that is, groundwater moves from higher ground to lower ground, following a slope, pulled by gravity. This makes sense, but is not always the case. In fact, groundwater also moves horizontally and even uphill, under hydrostatic pressure and the influence of capillary action. Groundwater moves much slower than does surface water, but it can potentially move huge distances. The speed of groundwater movement depends on the slope of the geologic formation in which the groundwater is contained and the composition of the strata. Water passes through fine sand at a rate of several centimetres a day, but will move several metres per day through gravel in the same time period. Cracks or joints in granite and sandstone link like great subterranean piping systems that can transmit water quickly in huge quantities. Groundwater StorageIn some areas, aquifers store water that has accumulated through thousands of years. In dry areas, such areas are in danger of permanent depletion of the aquifer due to heavy use of water mining. This is not the case in the Atlantic provinces, where abundant rainfall and snowmelt recharge both surface and groundwater. It is estimates, for example, that 20% of the total rainfall in Prince Edward Island becomes groundwater. Streams and lakes overlying permeable beds also recharge the water table. But more commonly, the presence of surface water is an indication of abundant groundwater supplies. During periods of little rain, for instance, water flowing in a stream may come almost entirely from groundwater. Have you ever heard of water "going underground" in periods of drought? In fact, such surface waters were always rooted in groundwater – lowering groundwater stocks in dry periods do not allow the groundwater stock to support a surface body. Even though aquifers are underground, they are closely connected with the movement of surface water in the natural drainage basin. The largest and best aquifers in Nova Scotia occur in valleys, such as the Annapolis-Cornwallis Valley, the North River valley near Truro, and the Musquodoboit Valley, where glacial and stream movements have left deposits of sand and gravel. The area around Halifax-Dartmouth is underlain by fractured granite, slate and quartzite. Wells in this region yield 4.5 - 23 litres of water per minute (typically) which is sufficient for a single family dwelling. Fully 50% of the fresh water used in Nova Scotia comes from wells. Many parts of New Brunswick and Nova Scotia (Cape Breton in particular) display a geological formation called the Windsor Group. This formation underlies almost a quarter of each of the two provinces, and while it is known to be a good aquifer, it's water is exceptionally hard due to a heavy limestone concentration. Groundwater QualityAs water infiltrates the ground, soil particles filter out bacteria and debris. Once underground, stored water is less vulnerable than surface water to airborne pollutants like dust, acid rain and industrial contaminants. Groundwater has other advantages over surface water, including a consistent temperature and continuous availability, even during dry spells. Domestic wells often provide water where no surface or municipal water is accessible or available. Water moving through the different levels of strata dissolves minerals which give it taste, colour and hardness. Just the right amount of dissolved minerals makes water tangy and beneficial to health, but too much makes it undesirable for certain uses. Groundwater containing dissolved metallic ions, particularly calcium and magnesium, is called hard water. These ions affect the chemical action of soap so that it will not lather easily. Hard water leaves a scaly deposit on the inside of kettles, pipes and boilers, which makes it unfit for some industrial uses. Excess iron in groundwater causes rusty stains on fixtures and clothing. Both iron and hardness may be removed by domestic or industrial water softeners. Saltwater intrusion is a particular groundwater quality problem in Atlantic coastal regions. This can occur in wells constructed close to the ocean. Normally, pressure from the underground fresh water will confine sea water to a zone of diffusion, where fresh and salt water meet. However, during dry periods, water withdrawn by prolonged well use relaxes the seaward pressure and allows salt water to move underground toward the area of the well. Hydrologists advise seaside residents to sink wells less deeply than normal and reduce pumping volumes during dry period to prevent saltwater intrusion. In areas where the problem is severe, controls may be necessary to limit the number of wells and thus reduce over pumping. Aquatic EcosystemsIn nature, nothing exists alone. Living things relate to each other as well as to their non-living, but supporting, environments. These complex relationships are called ecosystems. Each body of water is a delicately balanced ecosystem in continuous interaction with the surrounding air and land. WetlandsAny area covered by water, or where water is close to the surface of the land for all or part of the year, is called a wetland. To some people, wetlands are nothing more than areas of soggy ground. Bogs, swamps and marshes across Nova Scotia have been filled in or dredged for use as parking lots and roadways, and have even been used as dumping grounds for municipal and industrial wastes. Wetlands are not unproductive wastelands. Wetlands play a vital role in nature and their existence provides great benefit to humankind. Wetlands support and maintain a variety of plant and animal life; are of great recreational and economic importance to humans; and help maintain and replenish our water supplies. Water from rain or melting snow is held on the surface of wetlands, ponds and shallow lakes year-round. Gradually this water soaks into the soil beneath until it meets rock or impervious clay and can go no farther. From this underground reservoir, groundwater is available for plant growth, and to maintain water levels in lakes, ponds and streams. This water also supplies water for wells and other systems. In early spring, Nova Scotian groundwater tables are generally high. In the fall, groundwater levels are lowest because of the demands of vegetation and humans during the hot summer growing season. After a dry summer, groundwater levels may drop further than usual, resulting in stunted plant growth and dry wells. Wetlands serve to recharge groundwater levels. A ten acre lake contains about 3.5 million gallons of water per foot of depth. A 10 acre bog may be as much as 80% water, and so can store almost as much water per foot as a lake. Wetlands also serve as traps and reservoirs for valuable nutrients washed down from uplands by rain and melting snow. These nutrients support the growth of vegetation, which, in turn, supports many kinds of wildlife. Numerous upland game birds (duck, grouse, pheasant, and song birds) as well as deer, moose, and small game require wetland habitats for water and food. Coastal wetlands are important breeding grounds for wild fowl, coastal fish stocks and shellfish. Tidal flooding brings breeding fish, fish eggs, fry, and young fish into the salt marsh. Nutrients, washed from the uplands or brought in by the incoming tides, are trapped where the fresh and salt water meet, providing a rich supply of the materials required for growth. The outgoing tide takes away waste products, as well as the plant and animal life nurtured in the shelter of the salt marsh. Not only does the salt marsh and estuary restock the offshore fishery with young, it also provides food for larger marine species which may eventually find their way into fishers' nets and into our food web. The fishing industry depends on salt marsh breeding grounds to assure continuing fish stocks. For the same reason, recreational fishing is also dependent on the salt marsh, as is the inshore shellfish industry. All three fisheries are important to Nova Scotia's economy. Also important are the ducks, geese, muskrats and other economic species which use the salt marsh as breeding and feeding grounds. Kinds of Wetlands in Nova ScotiaWetlands are distinguished on the basis of the plant and wildlife species they support, as well as by their geographic location. Coastal Salt Marshes are subject to tidal flooding and are characterized by a species of cord grass called spartina. Inland Fresh Water Marshes are seasonally flooded, and generally have a water table at, or near, the marsh surface. The degree of wetness of the marsh is indicated by the presence of cattails (in the wettest marshes), rush, willow and red maple (in the driest marshes). Swamps are distinguished from other wetlands by the presence of sphagnum moss. They are primarily upland freshwater wetlands, and usually occur as a result of natural infilling of a lake or pond by sediment. In their later stages, they may support black or white spruce. Fens are inland, freshwater marshes common in lime rich areas. Coastal and inland wetlands provide a multitude of opportunities for hunters, fishers, and recreationists. Converting them to a singe use (for example, draining them to be used for agriculture) diminishes their total value. The fact that the economic value of wetlands is difficult to measure may account for the fact that their preservation has not been made a priority until lately. Perhaps one simple way to measure the value of wetlands is to consider the cost of losing them. For example, if your well goes dry because of the loss of an upslope reservoir of groundwater (your local swamp), there are a number of options open to you. You can drill your well deeper to meet the new groundwater level. You can have a tank truck bring in water to refill your well. If you live in or near an urban area, you may be able to hook into central services and receive piped-in water. All of these alternatives cost money. Wetlands are a valuable resource which should be protected and carefully managed so that they may continue to support diverse plant and wildlife species. Alterations to and contamination of wetland cannot always be reversed – these are delicate ecosystems, and human intrusion into wetlands should be carefully considered and minimized. How Does Water Clean Itself?Whatever occurs on the land and in the air also affects the water. If a substance enters a river or lake, the water can purify itself biologically – but only to a degree. Whether it is in the smallest stream or lake – or even in the ocean – the water can absorb only so much. It reaches a point where natural cleaning processes can no longer cope. Water is purified, in large part, by the routine actions of living organisms. Energy from sunlight drives the process of photosynthesis in aquatic plants, which produces oxygen as a by-product. Bacteria use this oxygen to break down some of the organic material, such as plant and animal waste. Decomposition of plant and animal waste produces carbon dioxide, nutrients and other substances needed by plants and animals living in the water. The purification cycle continued when these plants and animals die and the bacteria decompose them, providing new generations of organisms with nourishment. Unfortunately, there are many toxic substances which are affected only slowly, or not at all, by this and other purification processes. These persistent substances are of great environmental concern. ActivitiesKeeping Pond Specimens – Some Tips!Setting up an aquatic habitat in the classroom (teacher focus) If you intend to collect specimens for classroom use, it's best to make preparations well in advance of your field trip. You will need clean containers to collect your specimens, samples of their native water, you may need a fish/aquarium net to capture your specimens, and you'll certainly need a holding tank for your specimens once you've returned to the classroom. And remember, its best to keep pond specimens for a very short period of time (a day or two) if you're not familiar with the specimens' habits. For more information about keeping pond specimens, see the Nova Scotia Museum Info Sheet, "A Native Freshwater Aquarium". Please note: The keeping of captive wildlife from nature is regulated by the Department of Natural Resources, because some animal populations are declining. Captive Wildlife Permits will not be issued for native species of reptiles and amphibians, but individuals may temporarily keep small numbers of amphibians for educational purposes without a permit (see "Tadpole Talk", below). Contact any Department of Natural Resources Regional Office for more information on Captive Wildlife.
What Can I Do to Improve Water Quality?More Water Facts (Parental / Adult focus) Each individual effort to protect water quality is vital. Individual actions can and do make a difference to water quality and to the environment as a whole. You can start by taking the following actions: Avoid hazardous household productsMost household chemicals are safe to use and are environmentally friendly when used according to the directions on the package. However, some have a harmful cumulative effect on the environment when they are over-used or incorrectly disposed of.
Don't Misuse the Sewage SystemDon't throw waste down the drain just because it's convenient. Toxic household products can damage the environment and return to us though water and food.
Don't use pesticides or other hazardous materials in your garden
Don't dump hazardous products into storm drainsStorm drains empty directly into nearby streams in many areas. The contents of storm sewers are generally not processed at sewage treatment facilities and can therefore do immediate harm to fish and wildlife. Beach closures are a typical example of storm water pollution in many communities.
Don't forget about water quality – even when you're having fun!
Groundwater QualityGrades 4, 5, 6 – Science PurposeStudents will learn how water is stored in groundwater aquifers and how pollutants enter our groundwater. The best aquifers are composed of gravel or coarse sand and gravel mixtures. In some aquifers, water is buried just beneath the land's surface, while in others, the water may be buried up to several hundred feet. There are still other areas where groundwater exists, but is either buried too deeply to pump out or is of too poor a quality to be of value. In some areas, no groundwater exists. Aquifers can be recharged when water percolates downward from streams, lakes, and even from rainfall on the soil surface. Water percolating through the soil and through the geologic formations can carry pollutants into the groundwater supply. Good quality water can be polluted through this process. Some types of pollutants that commonly enter groundwater supplies include fertilizers, pesticides, soaps or detergents, sewage wastes, and fuels. Proper management of these substances will usually keep them out of our groundwater. Materials
Procedure
ExtensionsDiscuss management techniques for various types of pollutants:
Stream ScannersGrade 6 – Science PurposeStudents will investigate the quality of water in a stream, lake, or pond by examining chemical, physical and/or biological characteristics. Most plants and animals depend on clean water for healthy growth. A stream with good quality water supports a variety of plants and animals. Water polluted by chemicals or organic matter often supports only a few kinds of plants and animals. If the pollution is severe, the stream water may kill all life around it. Biologists can assess stream quality in a number of ways: visually by documenting the surrounding physical habitat, chemically by testing the water for specific pollutants, biologically by noticing types of plant and animal species present. Healthy streams have a pH of about 7.0, clear water, and a temperature lower than 20°C. Nitrate concentrations are below one part per million; phosphate levels are below 0.03 parts per million. Materials
Procedure
Wells: A Deep SubjectGrades 4, 5, 6 – Science, Mathematics PurposeStudents will discover and explain how a well works and examine the well's relationship to the water table. Students will further apply the principles of well placement. About a quarter of us get our drinking water from groundwater. A well is a hold in the ground that reaches into groundwater. In ancient times, these wells were dug by hand and lined with stones or bricks to prevent the sides from collapsing. Today, most are formed by drilling a 5 - 10 cm hole and lining it with metal or plastic piping. A well must be dug deeper than the water table (the top surface of the saturated zone). Water is usually pumped by hand, by windmill, or by a motor-driven device. The biggest problem facing well water is contamination. Sources of groundwater pollution include: leaking underground storage tanks; leaking septic tanks; landfill seepage; animal wastes; fertilizer; pesticides; industrial waste; road salt; and some naturally occurring contaminants. When a groundwater source is contaminated, it is very difficult and expensive to de-contaminate. The best way to protect well water is to prevent contamination from occurring. Wells should be properly located in order to avoid contact with contaminants. MaterialsListed are materials sufficient for one demonstration
ProcedurePrepare the well for demonstration by cutting the top off the plastic bottle and filling its bottom with gravel. Position the pump in the bottle. Ask the students about wishes – what are wishes, and if someone could give you one wish, what would you wish for? Where do you think you would to make a wish (a wishing well) and what would you have to do at a wishing well to have your wish granted? (throw in a coin). Explain that wells, in some cultures, are believed to hold "magical" powers. Why? Because people were amazed that water could come up through the ground, appearing from deep within the earth. They developed rituals and superstitions about wells. Explain the importance of wells today – that about half of us get their water from wells. Explain that while most wells are safe, they can become contaminated or polluted. ActivityPosition the demonstration so that all may observe, or have the students do this activity in small groups, each with their own set of materials. Pour sand in the bottle, so that there is about 10 cm of gravel and sand in the bottle bottom. Pour in about 7 cm of water, coloured with blue food colouring. While the water is being carefully poured into the bottle, explain that water found beneath the ground is called groundwater. Explain that the top surface of the saturated zone is called the water table. Mark the level of the water table on the outside of the bottle, using the marker. Sink your well, so that the long tube of the pump is embedded in the gravel (you'll know it is by feel), but not so deep that the tube touches the bottom of the bottle. Tell the students that today, a well is usually drilled. Tell them that the well is usually between 5 and 10 centimetres wide and is lined with a metal or plastic pipe. Ask them why they think the well needs to be lined (to keep the dirt / sides from falling in). Ask the students to notice that for the well to work, the tubing must extend below the water table. Pump water out of the model (catching the water in a cup). Ask the question, "when we take water out of the ground, what happens to the water table?" (It goes down). Mark the new level of the water table with a marker on the outside of the bottle. Ask the students how water gets back into the groundwater supply (recharge – when it rains, when snow melts into the ground). Demonstrate recharge by pouring more of the blue water back in to the ground until the level of the original water table is restored. Remind students that some groundwater sources cannot be replenished because they are sealed both above and below by solid rock or another ground material that will not let water soak through. Explain to the students that just as the rain water or snow melt can soak down into the groundwater, so can harmful contaminants like agricultural waste, sewage, road salt, and other chemicals. Pour water coloured with yellow food colouring into the bottle. Ask the students to describe what has happened to the "groundwater" (it changed colour – greenish – after the "contaminated" water reached it). Pump some of the "new" water into another cup (the blue water is water that was already in the pipe when the contaminated water was added to the groundwater). Explain to the students that while many contaminants can be seen, others cannot. Ask the students how they would determine if well water was contaminated (by testing the water). Explain that contaminants are not always of human origin – some are naturally occurring. ExtensionsHave the students draw a cross-section of a well (or their well) and the water table. Instruct them to write a sentence or two describing how a well affects the water table. Ask the students to list at least four possible sources of groundwater contamination. Students may research legends, folklore and superstitions about wells . Research may result in an ELA assignment of a modern-day well "legend". Ask the students to contact the Department of Health and/or the Department of Natural Resource for information and guidelines about digging new wells. Making Drinking WaterGrades 4, 5, 6 – Science, Social Studies PurposeStudents will learn about methods of purifying water used by early settlers, as well as those used currently in water treatment facilities. Early settlers learned (the hard way) to drink from flowing waters and not to drink from still waters. And while the water in lakes, rivers, and streams often contained impurities that made them look and smell bad, sometimes their water could be "cleaned" to make it safer to drink. Early settlers used citric acid or alum, which clung to suspended particles and made them sink to the bottom of a water vessel. Simply allowing the water to sit for several hours also took out some (solid) impurities. Finally, the settlers would strain the water through material to extract the rest of the nasty bits. To further purify the water, particularly if disease were suspect, settlers boiled their water before drinking it. Several of these methods are currently used by water companies to treat our drinking water. The water that is processed in treatment facilities comes from lakes, rivers, streams, or aquifers and has usually been transferred and stored before it is processed. The following steps are typical in a water treatment plant: Aeration Coagulation Sedimentation Filtration Chlorination Materials(per group or per classroom)
ProcedureIf you wish, you may allow the water to settle, so that the students can see the effect of sedimentation on dirty water. You may also choose to demonstrate only sedimentation and skip using the alum (particularly with the lower grades), but using alum allows the students to see how citric acid worked for the early settlers. You should allow several hours for sedimentation to occur (it's best to leave the vessel overnight). Discuss water purification. Talk to the students about how our drinking water is purified before we drink it – even groundwater is cleaned, naturally, as it filters through the soil. If the class is divided into groups, pass out one clear plastic cup with water that has ½ tsp of dirt mixed in it. Or use muddy water from a local stream (or even a puddle in the school yard). Review the steps in the water purification process and discuss how the modern methods compare to or contrast with those used by our early settlers and Aboriginal peoples. The students can "aerate" the water by pouring it back and forth between two cups. Ask the students to add ½ tsp of alum and watch the floc form. Allow the glass to sit undisturbed for several minutes. At this point, you may wish to discuss sedimentation. Next, have the students hold a piece of cheesecloth over the empty glass and pour the water through the cheesecloth into another glass or a larger bowl (opt for the larger bowl with early grades). Have the students examine the cheesecloth. Pour the filtered water through the second piece of cheesecloth. Examine the differences between the two pieces of material. Discuss the pioneer's final step of boiling out impurities, and compare that step to our modern method of adding chemicals to purify water. Which do the student's think is the better method? The more environmentally-friendly method? Which method would they prefer to use? Which method is more practical in the modern age? ExtensionsGo on a field trip to a water treatment plant or invite someone from such a facility to visit the class. Mix up and compare the various processes used in water treatment / purification. Are there other methods that the students know of? Research how water is purified for use in other cultures and/or in developing nations. Is water always purified before use? Notes:
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