A day in the life of a scientist

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Where does our drinking water come from?

K-4 class presentation: click here>>
Water cycle.

30-40 minute Class presentation on the water cycle. Fun activities for the children are included that will spark the children’s curiosity.

30-40 minute class presentation discussing groundwater and what an aqufer is. Fun activities that will spark the children’s curiosity are included.

The Water Cycle.

Flash animation – interactive groundwater cycle. Groundwater

Credit for this water class: U.S. Geological Survey Department of the Interior/USGS

Earth’s water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years.

The topics below are covered by the USGS in an easy to understand manner. We recommend that you look through these topics prior your DILOS field trip. It will help you understand a bit of what we will be doing during our research and water / sediment sampling.

Follow a Drop Through the Water Cycle

You may be familiar with how water is always cycling around, through, and above the Earth, continually changing from liquid water to water vapor to ice. One way to envision the water cycle is to follow a drop of water around as it moves on its way. I could really begin this story anywhere along the cycle, but I think the ocean is the best place to start, since that is where most of Earth’s water is.

If the drop wanted to stay in the ocean then it shouldn’t have been sunbathing on the surface of the sea. The heat from the sun found the drop, warmed it, and evaporated it into water vapor. It rose (as tiny “dropettes”) into the air and continued rising until strong winds aloft grabbed it and took it hundreds of miles until it was over land. There, warm updrafts coming from the heated land surface took the dropettes (now water vapor) up even higher, where the air is quite cold.

When the vapor got cold it changed back into it a liquid (the process is condensation). If it was cold enough, it would have turned into tiny ice crystals, such as those that make up cirrus clouds. The vapor condenses on tiny particles of dust, smoke, and salt crystals to become part of a cloud.

After a while our drop combined with other drops to form a bigger drop and fell to the earth as precipitation. Earth’s gravity helped to pull it down to the surface. Once it starts falling there are many places for water drops to go. Maybe it would land on a leaf in a tree, in which case it would probably evaporate and begin its process of heading for the clouds again. If it misses a leaf there are still plenty of places to go.

The drop could land on a patch of dry dirt in a flat field. In this case it might sink into the ground to begin its journey down into an underground aquifer as groundwater. The drop will continue moving (mainly downhill) as groundwater, but the journey might end up taking tens of thousands of years until it finds its way back out of the ground. Then again, the drop could be pumped out of the ground via a water well and be sprayed on crops (where it will either evaporate, flow along the ground into a stream, or go back down into the ground). Or the well water containing the drop could end up in a baby’s drinking bottle or be sent to wash a car or a dog. From these places, it is back again either into the air, down sewers into rivers and eventually into the ocean, or back into the ground.

But our drop may be a land-lover. Plenty of precipitation ends up staying on the earth’s surface to become a component of surface water. If the drop lands in an urban area it might hit your house’s roof, go down the gutter and your driveway to the curb. If a dog or squirrel doesn’t lap it up it will run down the curb into a storm sewer and end up in a small creek. It is likely the creek will flow into a larger river and the drop will begin its journey back towards the ocean.

If no one interferes, the trip will be fast (speaking in “drop time”) back to the ocean, or at least to a lake where evaporation could again take over. But, with billions of people worldwide needing water for most everything, there is a good chance that our drop will get picked up and used before it gets back to the sea.

A lot of surface water is used for irrigation. Even more is used by power-production facilities to cool their electrical equipment. From there it might go into the cooling tower to be evaporated. Talk about a quick trip back into the atmosphere as water vapor — this is it. But maybe a town pumped the drop out of the river and into a water tank. From here the drop could go on to help wash your dishes, fight a fire, water the tomatoes, or (shudder) flush your toilet. Maybe the local steel mill will grab the drop, or it might end up at a fancy restaurant mopping the floor. The possibilities are endless — but it doesn’t matter to the drop, because eventually it will get back into the environment. From there it will again continue its cycle into and then out of the clouds, this time maybe to end up in the water glass of the President of the United States.

Ground Water

Some water underlies the Earth’s surface almost everywhere, beneath hills, mountains, plains, and deserts. It is not always accessible, or fresh enough for use without treatment, and it’s sometimes difficult to locate or to measure and describe. This water may occur close to the land surface, as in a marsh, or it may lie many hundreds of feet below the surface, as in some arid areas of the West. Water at very shallow depths might be just a few hours old; at moderate depth, it may be 100 years old; and at great depth or after having flowed long distances from places of entry, water may be several thousands of years old.

Ground water is stored in, and moves slowly through, moderately to highly permeable rocks called aquifers. The word aquifer comes from the two Latin words, aqua, or water, and ferre, to bear or carry. Aquifers literally carry water underground. An aquifer may be a layer of gravel or sand, a layer of sandstone or cavernous limestone, a rubbly top or base of lava flows, or even a large body of massive rock, such as fractured granite, that has sizable openings. In terms of storage at any one instant in time, ground water is the largest single supply of fresh water available for use by humans.

Springs in Snake River Plain, Idaho.

Ground water has been known to humans for thousands of years. Scripture (Genesis 7:11) on the Biblical Flood states that “the fountains of the great deep (were) broken up,” and Exodus, among its many references to water and to wells, refers (20:4) to “water under the Earth.” Many other ancient chronicles show that humans have long known that much water is contained underground, but it is only within recent decades that scientists and engineers have learned to estimate how much ground water is stored underground and have begun to document its vast potential for use. An estimated one million cubic miles of the world’s ground water is stored within one-half mile of the land surface. Only a fraction of this reservoir of ground water, however, can be practicably tapped and made available on a perennial basis through wells and springs. The amount of ground water in storage is more than 30 times greater than the nearly 30,000 cubic-miles volume in all the fresh-water lakes and more than the 300 cubic miles of water in all the world’s streams at any given time.

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Comparison of the amount of fresh water in storage.

How Ground Water Occurs

It is difficult to visualize water underground. Some people believe that ground water collects in underground lakes or flows in underground rivers. In fact, ground water is simply the subsurface water that fully saturates pores or cracks in soils and rocks. Ground water is replenished by precipitation and, depending on the local climate and geology, is unevenly distributed in both quantity and quality. When rain falls or snow melts, some of the water evaporates, some is transpired by plants, some flows overland and collects in streams, and some infiltrates into the pores or cracks of the soil and rocks. The first water that enters the soil replaces water that has been evaporated or used by plants during a preceding dry period. Between the land surface and the aquifer water is a zone that hydrologists call the unsaturated zone. In this unsaturated zone, there usually is at least a little water, mostly in smaller openings of the soil and rock; the larger openings usually contain air instead of water. After a significant rain, the zone may be almost saturated; after a long dry spell, it may be almost dry. Some water is held in the unsaturated zone by molecular attraction, and it will not flow toward or enter a well. Similar forces hold enough water in a wet towel to make it feel damp after it has stopped dripping.

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How ground water occurs in rocks.

After the water requirements for plant and soil are satisfied, any excess water will infiltrate to the water table–the top of the zone below which the openings in rocks are saturated. Below the water table, all the openings in the rocks are full of water that moves through the aquifer to streams, springs, or wells from which water is being withdrawn. Natural refilling of aquifers at depth is a slow process because ground water moves slowly through the unsaturated zone and the aquifer. The rate of recharge is also an important consideration. It has been estimated, for example, that if the aquifer that underlies the High Plains of Texas and New Mexico–an area of slight precipitation–was emptied, it would take centuries to refill the aquifer at the present small rate of replenishment. In contrast, a shallow aquifer in an area of substantial precipitation may be replenished almost immediately.

Aquifers can be replenished artificially. For example, large volumes of ground water used for air conditioning are returned to aquifers through recharge wells on Long Island, New York. Aquifers may be artificially recharged in two main ways: One way is to spread water over the land in pits, furrows, or ditches, or to erect small dams in stream channels to detain and deflect surface runoff, thereby allowing it to infiltrate to the aquifer; the other way is to construct recharge wells and inject water directly into an aquifer as shown on page 10. The latter is a more expensive method but may be justified where the spreading method is not feasible. Although some artificial-recharge projects have been successful, others have been disappointments; there is still much to be learned about different ground-water environments and their receptivity to artificial-recharge practices.

A well, in simple concept, may be regarded as nothing more than an extra large pore in the rock. A well dug or drilled into saturated rocks will fill with water approximately to the level of the water table. If water is pumped from a well, gravity will force water to move from the saturated rocks into the well to replace the pumped water. This leads to the question: Will water be forced in fast enough under a pumping stress to assure a continuing water supply? Some rock, such as clay or solid granite, may have only a few hairline cracks through which water can move. Obviously, such rocks transmit only small quantities of water and are poor aquifers. By comparison, rocks such as fractured sandstones and cavernous limestone have large connected openings that permit water to move more freely; such rocks transmit larger quantities of water and are good aquifers. The amounts of water that an aquifer will yield to a well may range from a few hundred gallons a day to as much as several million gallons a day.

Quality of Ground Water

For the Nation as a whole, the chemical and biological character of ground water is acceptable for most uses. The quality of ground water in some parts of the country, particularly shallow ground water, is changing as a result of human activities. Ground water is less susceptible to bacterial pollution than surface water because the soil and rocks through which ground water flows screen out most of the bacteria. Bacteria, however, occasionally find their way into ground water, sometimes in dangerously high concentrations. But freedom from bacterial pollution alone does not mean that the water is fit to drink. Many unseen dissolved mineral and organic constituents are present in ground water in various concentrations. Most are harmless or even beneficial; though occurring infrequently, others are harmful, and a few may be highly toxic.

Water is a solvent and dissolves minerals from the rocks with which it comes in contact. Ground water may contain dissolved minerals and gases that give it the tangy taste enjoyed by many people. Without these minerals and gases, the water would taste flat. The most common dissolved mineral substances are sodium, calcium, magnesium, potassium, chloride, bicarbonate, and sulfate. In water chemistry, these substances are called common constituents.

Water typically is not considered desirable for drinking if the quantity of dissolved minerals exceeds 1,000 mg/L (milligrams per liter). Water with a few thousand mg/L of dissolved minerals is classed as slightly saline, but it is sometimes used in areas where less-mineralized water is not available. Water from some wells and springs contains very large concentrations of dissolved minerals and cannot be tolerated by humans and other animals or plants. Many parts of the Nation are underlain at depth by highly saline ground water that has only very limited uses.

Dissolved mineral constituents can be hazardous to animals or plants in large concentrations; for example, too much sodium in the water may be harmful to people who have heart trouble. Boron is a mineral that is good for plants in small amounts, but is toxic to some plants in only slightly larger concentrations.

Water that contains a lot of calcium and magnesium is said to be hard. The hardness of water is expressed in terms of the amount of calcium carbonate-the principal constituent of limestone-or equivalent minerals that would be formed if the water were evaporated. Water is considered soft if it contains 0 to 60 mg/L of hardness, moderately hard from 61 to 120 mg/L, hard between 121 and 180 mg/L, and very hard if more than 180 mg/L. Very hard water is not desirable for many domestic uses; it will leave a scaly deposit on the inside of pipes, boilers, and tanks. Hard water can be softened at a fairly reasonable cost, but it is not always desirable to remove all the minerals that make water hard. Extremely soft water is likely to corrode metals, although it is preferred for laundering, dishwashing, and bathing.

Ground water, especially if the water is acidic, in many places contains excessive amounts of iron. Iron causes reddish stains on plumbing fixtures and clothing. Like hardness, excessive iron content can be reduced by treatment. A test of the acidity of water is pH, which is a measure of the hydrogen-ion concentration. The pH scale ranges from 0 to 14. A pH of 7 indicates neutral water; greater than 7, the water is basic; less than 7, it is acidic. A one unit change in pH represents a 10-fold difference in hydrogen-ion concentration. For example, water with a pH of 6 has 10 times more hydrogen-ions than water with a pH of 7. Water that is basic can form scale; acidic water can corrode. According to U.S. Environmental Protection Agency criteria, water for domestic use should have a pH between 5.5 and 9.

In recent years, the growth of industry, technology, population, and water use has increased the stress upon both our land and water resources. Locally, the quality of ground water has been degraded. Municipal and industrial wastes and chemical fertilizers, herbicides, and pesticides not properly contained have entered the soil, infiltrated some aquifers, and degraded the ground-water quality. Other pollution problems include sewer leakage, faulty septic-tank operation, and landfill leachates. In some coastal areas, intensive pumping of fresh ground water has caused salt water to intrude into fresh-water aquifers.

How intensive ground-water pumping can cause salt-water intrusion in coastal aquifers.

In recognition of the potential for pollution, biological and chemical analyses are made routinely on municipal and industrial water supplies. Federal, State, and local agencies are taking steps to increase water-quality monitoring. Analytical techniques have been refined so that early warning can be given, and plans can be implemented to mitigate or prevent water-quality hazards.

Appraising the Nation’s Ground-Water Resources

Although there are sizable areas where ground water is being withdrawn at rates that cause water levels to decline persistently, as in parts of the dry Southwest, this is not true throughout the country. For the Nation as a whole, there is neither a pronounced downward nor upward trend. Water levels rise in wet periods and decline in dry periods. In areas where water is not pumped from aquifers in excess of the amount of recharge to the aquifer–particularly in the humid central and eastern parts of the country–water levels average about the same as they did in the early part of the twentieth century.

A major responsibility of the U.S. Geological Survey is to assess the quantity and quality of the Nation’s water supplies. The Geological Survey, in cooperation with other Federal, State, and local agencies, maintains a nationwide hydrologic-data network, carries out a wide variety of water-resources investigations, and develops new methodologies for studying water. The results of these investigations are indispensable tools for those involved in water-resources planning and management. Numerous inquiries concerning water resources and hydrology are directed to the Survey and to State water-resources and geological agencies.

To locate ground water accurately and to determine the depth, quantity, and quality of the water, several techniques must be used, and a target area must be thoroughly tested and studied to identify hydrologic and geologic features important to the planning and management of the resource. The landscape may offer clues to the hydrologist about the occurrence of shallow ground water. Conditions for large quantities of shallow ground water are more favorable under valleys than under hills. In some regions–in parts of the arid Southwest, for example–the presence of “water-loving” plants, such as cottonwoods or willows, indicates ground water at shallow to moderate depth. Areas where water is at the surface as springs, seeps, swamps, or lakes reflect the presence of ground water, although not necessarily in large quantities or of usable quality.

Rocks are the most valuable clues of all. As a first step in locating favorable conditions for ground-water development, the hydrologist prepares geologic maps and cross sections showing the distribution and positions of the different kinds of rocks, both on the surface and underground. Some sedimentary rocks may extend many miles as aquifers of fairly uniform permeability. Other types of rocks may be cracked and broken and contain openings large enough to carry water. Types and orientation of joints or other fractures may be clues to obtaining useful amounts of ground water. Some rocks may be so folded and displaced that it is difficult to trace them underground.

Next, a hydrologist obtains information on the wells in the target area. The locations, depth to water, amount of water pumped, and types of rocks penetrated by wells also provide information on ground water. Wells are tested to determine the amount of water moving through the aquifer, the volume of water that can enter a well, and the effects of pumping on water levels in the area. Chemical analysis of water from wells provides information on quality of water in the aquifer.

Evaluating the ground-water resource in developed areas, prudent management of the resource, and protection of its quality are current ground-water problems. Thus, prediction of the capacity of the ground-water resource for long-term pumpage, the effects of that pumpage, and evaluation of water-quality conditions are among the principal aims of modern-day hydrologic practice in achieving proper management of ground water.

Ground water, presently a major source of water, is also the Nation’s principal reserve of fresh water. The public will have to make decisions regarding water supply and waste disposal-decisions that will either affect the ground-water resource or be affected by it. These decisions will be more judicious and reliable if they are based upon knowledge of the principles of ground-water occurrence

Fecal Coliform

What is it?

Fecal coliform bacteria are found in the feces of human beings and other warm-blooded animals. By themselves, fecal coliform bacteria do not usually cause disease. In fact, they are already inside you. They occur naturally in the human digestive tract and aid in the digestion of food. However, when a human being or other warm-blooded animal is infected with disease, pathogenic (disease causing) organisms are found along with fecal coliform bacteria.

Why does fecal coliform matter?

Think of high levels of fecal coliform bacteria as a warning sign that water can make you sick, rather than as a cause of illness. If fecal coliform counts are high (over 200 colonies/100 ml of a water sample) in a body of water, there is a greater chance that disease causing organisms are also present. If you are swimming in waters with high levels of fecal coliform, you have a greater chance of developing a fever, nausea or stomach cramps from swallowing disease-causing organisms, or from pathogens entering the body through cuts in the skin, the nose, mouth, or ears. Some examples of diseases and illnesses that can be contracted in water with high fecal coliform counts include
typhoid fever, hepatitis, gastroenteritis, dysentery and ear infections.

Fecal coliform bacteria are living organisms, unlike the other conventional water quality parameters. The fecal coliform bacteria multiply rapidly when conditions are good for growth and die in large quantities when they are not.

How does fecal coliform get in the water?

Untreated sewage, poorly maintained septic systems, un-scooped pet waste, and farm animals with access to streams can cause high levels of fecal coliform bacteria to appear in a water body.

Temperature

What is it?

Temperature is a measure of how much heat is present in the water.

Why does temperature matter?

Water temperature tells many things about the health of a river. Temperature affects:
1) Dissolved oxygen levels in water – Cold water holds more oxygen than warm water.
2) Photosynthesis – As temperature goes up, the rate of photosynthesis and plant growth also goes up. More plants grow and more plants die. When plants die, decomposers eat them and use oxygen. So when the rate of photosynthesis increases, the amount of oxygen needed by aquatic organisms increases.
3) Animal survival – Many animals need certain temperatures to live. For example, stonefly nymphs and trout need cool temperatures. Dragonfly nymphs and carp can live in warmer water. If water temperatures change too much, many organisms can no longer survive.
4) Sensitivity to toxic wastes and disease – Wastes often raise water temperatures. This leads to lower oxygen levels and weakens many fish and insects. Weakened animals get sick and die more easily.

How does water get warmer?

In the summer, the sun heats up sidewalks, parking lots and streets. Rain falls on these areas, warms up, and runs into the river. Factories and stations that generate electricity to cool their processes also use water. Warm water enters the river, raises the temperature of the downstream area and changes oxygen levels. These are forms of thermal pollution.

Thermal pollution is one of the most serious ways humans affect rivers. Cutting down trees along the bank of a river or pond also raises water temperature. Trees help shade the river from the sun. When they are cut down, the sun shines directly on the water and warms it up. Cutting down trees also leads to erosion. When soil from the riverbank washes into the river the water becomes muddy (turbid). The darker, turbid water captures more heat from the sun than clear water does. Even murky green water with lots of algae will be warmer than clear water.

Dissolved Oxygen (DO)

What is it?

Like people, aquatic organisms need oxygen to survive and stay healthy. In areas with waves, or where water tumbles over rocks, falling water traps oxygen and mixes it into the water. Unlike people, aquatic organisms breathe oxygen that is dissolved in water. To breathe underwater, fish and other aquatic organisms use gills instead of lungs. These gills breathe the oxygen dissolved in the water. As you know, a fish out of the water will die because it can no longer breathe.

Why does DO matter?

Imagine living in a place with polluted air. As the air quality becomes worse, the health of the people who live there becomes worse. The same is true in water. Clean, healthy water has plenty of DO. When water quality decreases, DO levels drop and it becomes impossible for many animals to survive. Some fish such as trout require lots of dissolved oxygen. Others such as carp can live in water with lower levels of DO. Warmer water holds less oxygen than cold water. Also, the time of year and many other factors affect the amount of DO in water.

How do DO levels in the water drop?

The main reason DO levels might fall is the presence of organic waste. Organic waste comes from something living or that was once living. It comes from raw or poorly treated sewage; runoff from farms and animal feedlots; and natural sources like decaying aquatic plants and animals and fallen leaves in water. Microscopic organisms, called decomposers, break down the organic waste and use
oxygen in the process. Two common types of decomposers are bacteria and protozoa. More waste means more decomposers and more oxygen being used. DO levels can also fall due to any human activity that heats the water.

pH

What is it?

pH is a measurement of the acidity or basic quality of water. For example, lemons, oranges and vinegar are high in acid (“very acidic”). Acids can sting or burn, which is what you feel when you eat some kinds of fruit with a sore in your mouth. The pH scale ranges from a value of 0 (very acidic) to 14 (very basic), with 7 being neutral. The pH of natural water is usually between 6.5 and 8.2

Why does the pH level matter?

At extremely high or low pH levels (for example 9.6 or 4.5), the water becomes unsuitable for most organisms. Young fish and insects are also very sensitive to changes in pH. Most aquatic organisms adapt to a specific pH level and may die if the pH of the water changes even slightly.

How do levels of pH become too high or low?

pH can vary from its normal levels (6.5 to 8.2) due to pollution from automobiles and coal-burning power plants. These sources of pollution help form acid rain. Acid forms when chemicals in the air combine with moisture in the atmosphere. It falls to earth as acid rain or snow. Many lakes in eastern Canada, the northeastern US, and northern Europe are becoming acidic because they are downwind of polluting industrial plants. Drainage from mines can seep into streams and ground water and make the water more acidic as well.

Amonia

What is it?

Ammonia or azane is a compound of nitrogen and hydrogen with the formula NH₃. It is a colorless gas with a characteristic pungent smell. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or indirectly, is also a building-block for the synthesis of many pharmaceuticals and is used in many commercial cleaning products. Although in wide use, ammonia is both caustic and hazardous. The global production of ammonia for 2012 is anticipated to be 198 million tonnes, a 35% increase over the estimated 2006 global output of 146.5 million tonnes^.

Why does it matter?

Ammonium ions are a toxic waste product of the metabolism in animals. In fish and aquatic invertebrates, it is excreted directly into the water. In mammals, sharks, and amphibians, it is converted in the urea cycle to urea, because it is less toxic and can be stored more efficiently. In birds, reptiles, and terrestrial snails, metabolic ammonium is converted into uric acid, which is solid, and can therefore be excreted with minimal water loss.^[1]

Toxicity

The toxicity of ammonia solutions does not usually cause problems for humans and other mammals, as a specific mechanism exists to prevent its build-up in the bloodstream. Ammonia is converted to carbamoyl phosphate by the enzyme carbamoyl phosphate synthetase, and then enters the urea cycle to be either incorporated into amino acids or excreted in the urine. However, fish and amphibians lack this mechanism, as they can usually eliminate ammonia from their bodies by direct excretion. Ammonia even at dilute concentrations is highly toxic to aquatic animals, and for this reason it is classified as dangerous for the environment.^[2]

Nitrate

What is it?

Nitrate compounds are found naturally on earth as large deposits, particularly of Chile saltpeter a major source of sodium nitrate. Nitrites are produced by a number of species of nitrifying bacteria, and the nitrate compounds for gunpowder were historically produced, in the absence of mineral nitrate sources, by means of various fermentation processes using urine and dung.

Why does it matter?

Marine toxicity

In freshwater or estuarine systems close to land, nitrate can reach high levels that can potentially cause the death of fish. While nitrate is much less toxic than ammonia, levels over 30 ppm of nitrate can inhibit growth, impair the immune system and cause stress in some aquatic species. However, in light of inherent problems with past protocols on acute nitrate toxicity experiments, the extent of nitrate toxicity has been the subject of recent debate.

In most cases of excess nitrate concentrations in aquatic systems, the primary source is surface runoff from agricultural or landscaped areas that have received excess nitrate fertilizer. This is called eutrophication and can lead to algae blooms. As well as leading to water anoxia and dead zones, these blooms may cause other changes to ecosystem function, favouring some groups of organisms over others. As a consequence, as nitrate forms a component of total dissolved solids, they are widely used as an indicator of water quality.

Nitrate also is a by-product of septic systems. To be specific, it is a naturally occurring chemical that is left after the breakdown or decomposition of animal or human waste. Water quality may also be affected through ground water resources that have a high number of septic systems in a watershed. Septics leach down into ground water resources or aquifers and supply nearby bodies of water. Lakes that rely on ground water are often affected by nitrification through this process.[3]

Human toxicity

Nitrate in drinking water at levels above the national standard poses an immediate threat to young children. Excessive levels can result in a condition known as “blue baby syndrome”. If untreated, the condition can be fatal. Boiling water contaminated with nitrate increases the nitrate concentration and the potential risk.

Nitrate toxicosis can occur through enterohepatic metabolism of nitrate to nitrite being an intermediate. Nitrites oxidize the iron atoms in hemoglobin from ferrous iron (2+) to ferric iron (3+), rendering it unable to carry oxygen. This process can lead to generalized lack of oxygen in organ tissue and a dangerous condition called methemoglobinemia. Although nitrite converts to ammonia, if there is more nitrite than can be converted, the animal slowly suffers from a lack of oxygen.[4]

Nitrite

What is it?

Nitrite (NO2) is the toxic by-product of the nitrifying bacteria (Nitrospira) in a filter or substrate consuming Ammonia. It is only mildly less toxic than Ammonia but it still can kill aquatic animals if its levels get too high. Like ammonia, the toxicity of nitrite is related to pH.

Two forms of nitrite are present in water: the nitrite ion (NO2-) and the more toxic nitrous acid (HNO2). The amount of each of these that will be present is pH dependent and as the pH decreases the HNO2 form prevails and is therefore more toxic. The form HNO2 can diffuse freely across gill membranes and is much more toxic than the nitrite ion.[5]

Why does it matter?

Nitrite poisoning is also known by aquarists as Brown Blood Disease. Nitrite damages the nervous system, liver, spleen, and kidneys of fish and other aquatic animals. Even low concentrations of 0.5mg/l over extended periods can cause long term damage. Nitrite binds the oxygen carrying hemoglobin in blood therefore fish can suffocate even if the oxygen in the tank is sufficient.

Given time (normally 3–4 weeks) in a normal process of a new tank cycling, nitrites are converted into the much less toxic nitrates by the nitrifying bacteria. However if the levels of nitrites do not come down, then the nitrites will cause the animals to struggle for oxygen as the nitrites damage the gills of fish and will cause long term damage to their immune systems and stress them greatly.

Methylene blue helps nitrite stricken aquatic animals by helping them to carry oxygen in their blood and can prevent deaths.

TDS

What is it?

Total Dissolved Solids (often abbreviated TDS) is a measure of the combined content of all inorganic and organic substances contained in a liquid in: molecular, ionized or micro-granular (colloidal sol) suspended form. Generally the operational definition is that the solids must be small enough to survive filtration through a sieve the size of two micrometer.

Total dissolved solids are normally discussed only for freshwater systems, as salinity comprises some of the ions constituting the definition of TDS. The principal application of TDS is in the study of water quality for streams, rivers and lakes, although TDS is not generally considered a primary pollutant (e.g. it is not deemed to be associated with health effects) it is used as an indication of aesthetic characteristics of drinking water and as an aggregate indicator of the presence of a broad array of chemical contaminants.

Why does it matter?

High TDS levels generally indicate hard water, which can cause scale buildup in pipes, valves, and filters, reducing performance and adding to system maintenance costs. These effects can be seen in aquariums, spas, swimming pools, and reverse osmosis water treatment systems. Typically, in these applications, total dissolved solids are tested frequently, and filtration membranes are checked in order to prevent adverse effects. Most aquatic ecosystems involving mixed fish fauna can tolerate TDS levels of 1000 mg/l [7]

Specific gravity

What is it?

Specific gravity is the relation of a substance’s density to the density of water. The specific gravity tells you if the substance will rise or sink in the water; those with a specific gravity greater than water’s will sink, and those with one less than water’s will float. Usually specific gravity refers to an object’s density when compared with the density of water, so this value is a ratio.

The specific gravity of a substance is calculated by dividing the specific gravity of that substance by the specific gravity of water. Thus, the specific gravity of pure water would be a number divided by itself, which will always equal one.

Types

The specific gravity of water depends on the type of water being measured. Pure water at 4 degrees Celsius has a specific gravity of one. If the water has salts in it, the water is denser and the specific gravity will be greater than one. Sea water, for instance, is denser than fresh or pure water. Water with a specific gravity of one has a weight of one gram per one milliliter.

Anything with a specific gravity less than 1 (indicating it is less dense than water) will float on water. Because specific gravity is temperature dependent (the lower the temperature the less the density), the specific gravity of ice is less than that of liquid water. This makes ice float. This is important because, for example, if ice did not float, lakes and other bodies of water in northern climates would be frozen over much of the year.

Here are some examples of various products and their specific gravity:

Water has a specific gravity of 1.

Orange essential oil has an approximate specific gravity of .89

Glycerin has an approximate specific gravity of 1.21

Sweet Almond oil has an approximate specific gravity of .92

Water has a specific gravity of 1 which means 1 fluid ounce weighs 1 ounce.

Orange essential oil has a specific gravity of .89 which means 1 fluid ounce weighs .89 ounce.

Glycerin has a specific gravity of 1.21 which means 1 fluid ounce weighs 1.21 ounces.

Sweet Almond has a specific gravity of .92 which means 1 fluid ounce weighs .92 ounce.

To get a general idea if the sample you want to test has a specific gravity of more than 1 or less than 1 you need a clear jar (mayo jar or canning jar), water and the item you wish to test. Fill the clear jar with water to about 3/4 full. Add a small amount of the sample you want to test. If the sample floats on top of the water the specific gravity is less than 1, if it sinks to the bottom the specific gravity is more than 1. If the sample disperses and you can’t tell then the product is water soluble and not a great candidate for this test.

Conductivity

What is it?

Conductivity is a measure of how well water can pass an electrical current. It is an indirect measure of the presence of inorganic dissolved solids such as chloride, nitrate, sulfate, phosphate, sodium, magnesium, calcium, iron and aluminum. The presence of these substances increases the conductivity of a body of water. Organic substances like oil, alcohol, and sugar do not conduct electricity very well, and thus have a low conductivity in water.

Electrical conductivity of water is directly related to the concentration of dissolved ionized solids in the water. Ions from the dissolved solids in water create the ability for that water to conduct an electrical current, which can be measured using a conventional conductivity meter or TDS meter. When correlated with laboratory TDS measurements, conductivity provides an approximate value for the TDS concentration, usually to within ten-percent accuracy.

Why does it matter?

Inorganic dissolved solids are essential ingredients for aquatic life. They regulate the flow of water in and out of organisms’ cells and are building blocks of the molecules necessary for life. A high concentration of dissolved solids, however, can cause water balance problems for aquatic organisms and decrease dissolved oxygen levels

Salinity

What is it?

Salinity is the saltiness or dissolved salt content (such as sodium chloride, magnesium and calcium sulfates, and bicarbonates) of a body of water or in soil.

When we measure the salinity of water, we look at how much dissolved salt is in the water, or the concentration of salt in the water. Concentration is the amount (by weight) of salt in water and can be expressed in parts per million (ppm). Here are the classes of water:

Fresh water – less than 1,000 ppm
Slightly saline water – From 1,000 ppm to 3,000 ppm
Moderately saline water – From 3,000 ppm to 10,000 ppm
Highly saline water – From 10,000 ppm to 35,000 ppm

Why does it matter?

Salinity affects chemical conditions within the freshwater waterways, particularly levels of dissolved oxygen and dissolved inorganic phosphorus in the water. The amount of oxygen that can dissolve in water, or solubility, decreases as salinity increases. The solubility of oxygen in seawater is about 20 percent less than it is in fresh water at the same temperature. Phosphorus, which sticks to particles in freshwater, is released as salinity increased. In tidal freshwater or low salinity reaches of estuaries, dissolved phosphorus is not readily available and tends to limit phytoplankton production.

Salinity affects the physical structure of freshwater waterways and influences patterns of circulation. Because salt water is denser than freshwater, layers of different salinities can form resulting in stratification of the water column. Stratification impedes mixing in freshwater waterways, and exacerbates problems such as low dissolved oxygen at the bottom.

Salinity tolerance leads to zonation in freshwater plants and animals. Freshwater organisms have different tolerances and responses to salinity changes. Many bottom-dwelling animals, like oysters and crabs, can tolerate some change in salinity, but salinities outside an acceptable range will negatively affect their growth and reproduction, and ultimately, their survival. Some groups of animals, such as the echinoderms, which include animals such as sea stars, brittle stars and sea cucumbers, have very few species living in freshwater waterways because of their low tolerance of reduced salinity.

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Credit for this junior water class: U.S. Geological Survey Department of the Interior/USGS

Global water distribution

For an estimated explanation of where Earth’s water exists, look at the chart below. By now, you know that the water cycle describes the movement of Earth’s water, so realize that the chart and table below represent the presence of Earth’s water at a single point in time. If you check back in a thousand or million years, no doubt these numbers will be different!

Notice how of the world’s total water supply of about 332.5 million cubic miles of water, over 96 percent is saline. And, of the total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Fresh surface-water sources, such as rivers and lakes, only constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about 1/150th of one percent of total water. Yet, rivers and lakes are the sources of most of the water people use everyday.

Source: Igor Shiklomanov’s chapter “World fresh water resources” in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World’s Fresh Water Resources (Oxford University Press, New York).

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Where is Earth’s water?

For a detailed explanation of where Earth’s water is, look at the data table below. Notice how of the world’s total water supply of about 333 million cubic miles (1,386 million cubic kilometers) of water, over 96 percent is saline. And, of the total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Thus, rivers and lakes that supply surface water for human uses only constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about 0.007 percent of total water, yet rivers are the source of most of the water people use.

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Credit for this junior water class: U.S. Geological Survey Department of the Interior/USGS

There is no resource more precious than water. There is also no resource that is misused, abused, and misunderstood the way water is. Safe, healthy drinking water and a stable food supply are at stake as our water supply is placed under greater and greater stress.

The picture might look grim, but opportunities to be more efficient abound. Many people have had water-saving etiquette pumped into them at one point or another, so hopefully we can make a good case for conserving water with practical, everyday water-saving strategies as well as some more high-tech approaches.

Note: Follow the guidelines or instructions you receive from your teacher and if a parent or other adult is going to assist you with the project, make sure that your teacher’s guidelines and instructions are explained to the person who is helping you before you start.

1. Select a project that is not too complex and research your idea first.
2. See if it is going to be feasible to do the project.
3. Select a project that is appropriate for your age, skills and knowledge.
4. Give yourself time; don’t linger until the last minute to begin the project.
5. Make sure that you include adequate content in your final presentation; remember a flashy exhibit lacking legitimate information will not impress judges.
6. Do not change the project end results to fit your theory (hypothesis.)
7. Do the work yourself with only limited help from an adult.
8. Be imaginative but be concise.
9. Enjoy yourself and remember that you are learning something new that you can now share with others.
10. Remember to stick to proper use of the scientific method.