Overview

There are two methods water moves from the ground to the atmosphere as part of the hydrologic cycle. Transpiration is basically evaporation of water from plant leaves. Studies have revealed that transpiration accounts for about 10% of the the moisture in the atmosphere, with oceans, seas, and other bodies of water (lakes, rivers, streams) providing nearly all of the remaining amount.

The student will observe the effect of transpiration as water is moved from the ground to the atmosphere.

Procedure

1. Place a large plastic bag over a living limb of a tree or large bush. (The limb should not touch the ground.)
2. Tie the open end of the bag around the tree or bush. Make sure there are no air leaks.
3. At the closed end of the bag, tie a rock to the bag so the bag is weighted and forms a collection point for the water.
4. After a predetermined time of your choosing (at least 2 hours after "bagging" the branch), poke a hole in the bag and collect and measure the water. Then remove the bag and rock from the branch.

Discussion

Plant transpiration is generally an invisible process as the water from the exiting the leaves evaporates quickly. The temperature inside the bag will increase with heating from the sun. However, the water vapor will condense back into water as it comes in contact with bag and begin to collect.

During a growing season, a leaf will transpire many times more water than its own weight. An acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day, and a large oak tree can transpire 40,000 gallons (151,000 liters) per year.

The amount of water that plants transpire varies greatly geographically and over time. There are a number of factors that determine transpiration rates:

• Transpiration rates go up as the temperature goes up, especially during the growing season, when the air is warmer due to stronger sunlight and warmer air masses.
• As the relative humidity of the air surrounding the plant rises the transpiration rate falls. It is easier for water to evaporate into dryer air than into more saturated air.
• Increased movement of the air around a plant will result in a higher transpiration rate. If there is no wind, the air around the leaf may not move very much, raising the humidity of the air around the leaf. The moving air result that the more saturated air close to the leaf is replaced by drier air.
• Plants transpire water at different rates. Some plants which grow in arid regions, such as cacti and succulents, transpire less water than other plants as a measure to conserve water.

While the water may have a bitter or harsh taste (depending on the type of tree or bush selected) it is safe to drink and can provide much needed drinking water in survival situations.

Live Weatherwise

Drink plenty of water and natural juices, even if you don't feel thirsty. Even under moderately strenuous outdoor activity, the rate your body can absorb fluids is less than the rate it loses water due to perspiration. However, if you have epilepsy or heart, kidney, or liver disease; are on fluid-restrictive diets; or have a problem with fluid retention should consult a doctor before increasing liquid intake.

During times of excessive heat stay indoors as much as possible. Spend time in an air conditioned space. Only two hours a day in an air-conditioned space can significantly reduce the risk of heat-related illness. Shopping Malls offer relief if your home is not air-conditioned. If air conditioning is not available, stay on the lowest floor out of the sunshine. Remember, electric fans do not cool, they just blow hot air around.

Wear loose-fitting clothes that cover as much skin as possible. Lightweight, light-colored clothing that reflects heat and sunlight and helps maintain normal body temperature. Protect face and head by wearing a wide-brimmed hat. Avoid too much sunshine. Sunburn slows the skin's ability to cool itself. Use a sun screen lotion with a high SPF rating.

Overview

There are three states of matter; gas, liquid, and solid. Water in our atmosphere exists in these three states constantly. As the temperature of water vapor (a gas) decreases, it will reach the point at which it turns into a liquid (called the dew point or the point at which dew forms). This change of state from a gas to a liquid is called condensation.

Using some ice and a glass, the students will chill the glass to the point where water from the atmosphere will condense on the outside of the glass. This demonstrate the change of state of water vapor to liquid.

Procedure

1. Fill the cups/jars with ice.
2. Add cold water to the cups/jars.
3. Let the cups/jar set for about 30 minutes.
4. Observe the outside of the glass for condensation.

Discussion

Ask the students where the water on the outside of the glass came from. The answer is from the atmosphere. As the water vapor molecules came in contact with the cold side of the glass, the temperature lowered to the dew point, condensing into a liquid.

The amount of water on the side of the glass depends upon the humidity which is the ratio of dry air to moist air. The higher the humidity the more moisture that air contains. The greater the moisture, the greater the water that can condense.

Live Weatherwise

Flash floods are the deadliest natural disaster in the world. They are caused by stationary or slow-moving thunderstorms that produce heavy rain over a small area.

Hilly and mountainous areas are especially vulnerable to flash floods, where steep terrain and narrow canyons can funnel heavy rain into small creeks and dry ravines, turning them into raging walls of water. Even on the prairie, normally-dry draws and low spots can fill with rushing water during very heavy rain.

Take time to develop a flood safety plan-for home, work, or school, and wherever you spend time during the summer. The National Weather Service has additional information about flood safety and a brochure "Floods and Flash Floods...The Awesome Power".

• Know the name of the county where you live and nearby rivers and streams. Keep a map so you know where storms that may cause flash flooding are.
• Determine if you are in a flood-prone area. If you are, know where to go if the water starts to rise. Have an escape route if you have to leave quickly.
• Make a safety kit containing: A flashlight and extra batteries, battery-powered weather radio receiver and commercial radio, extra food and water, first-aid supplies, canned food and a can opener, water (three gallons per person), extra clothing, and bedding. Don't forget special items for family members such as diapers, baby formula, prescription or essential medications, extra eyeglasses or hearing aids, and pet supplies.
• Know how and when to shut off utilities: Electricity, gas, and water.
• Seek sources for obtaining local warning information such as from cable TV or the NOAA Weather Radio.

Overview

What goes up, must come down. Precipitation is the most commonly seen aspect of the hydrologic cycle. Students will learn how the water cycle works using 3-D paper craft activity. The students will see a demonstration the concept of precipitation.

Procedure

1. Add about two inches (5 cm) of hot water to the mayonnaise jar.
2. Add the ice cubes to the sandwich bag and seal it.
3. Place the sandwich bag over the mouth of the jar, allowing one end of the bag to form a tip inside of the jar. This will allow the condensed water to collect at one location.
4. After a few minutes, the water (rain) will begin to drip from the sandwich bag, returning to the water.

Discussion

Water vapor will rise from the hot water and come into contact with the bag fill with ice. The ice will cause the water to condense forming drops which will drop back into the water.

Despite the sometimes excessive rainfall that occurs, only about 0.3% of all water on the earth is found in the atmosphere. And only a small fraction of that is seen as rain. Most of the water in the atmosphere is in the gas state called water vapor

So while the hydrologic cycle is essential for life due to the water it brings, the vast amount of water in the cycle is found in the oceans, lakes, and ground water.

Live Weatherwise

• If a flash flood warning is issued, get to higher ground immediately! Follow evacuation instructions, but don't wait for them if you think you are in danger.
• Do not drive across flooded roads or bridges-they may be washed out.
• If your vehicle stalls in water, abandon it and get to higher ground. It takes only a foot or two of rapidly-moving water to sweep away a car.
• Walking or playing around flood waters is dangerous; you can be knocked from your feet in water only six inches deep!

Overview

Water is the most abundant and important substance on Earth. It is essential to life and is a major component of all living things. There are approximately 336,000,000,000,000,000,000 gallons of water on the earth, existing in three states; solid, liquid and gas.

The sources for this water storage are the oceans, icecaps & glaciers, ground water, fresh-water lakes, inland seas, soil moisture, atmosphere, and rivers. The students will discover the different water ratios in the earth's total water supply.

Procedure

1. Label beaker #1 "oceans" and fill it with 1000 ml of water.
2. Label the following beakers: beaker #2 "glaciers & icecaps", beaker #3 "groundwater", beaker #4 "fresh-water lakes", beaker #5 "inland seas", beaker #6 "soil moisture", beaker #7 "atmosphere", and beaker #8 "rivers".
3. Inform the students to assume the earth's total water supply has been reduced to 1000 ml as indicated in beaker #1.
4. Ask the students how much water must be transferred from beaker #1 into each of the remaining beakers representing the portion of water in each section. Write their estimates on the chalk board.
5. Transfer the following amounts of water FROM beaker #1 to each of the remaining beakers.
   1. Glaciers & icecaps - 21.4 ml
   2. Groundwater - 6.1 ml
   3. Fresh-water lakes - 0.09 ml (∼2 drops)
   4. Inland seas - 0.08 ml (1½ drops)
   5. Soil moisture - 0.05 ml (one drop)
   6. Atmosphere - 0.01 ml (0.2 drop)
   7. Rivers - 0.001 ml (0.02 drop)

Obviously, the last two, atmosphere and river, will be nearly impossible to obtain. So, by adding no drops will help in the students understanding of how little water is in those two locations.

Discussion

The students will be surprised how little water is found in each of the remaining beakers. The vast majority of water is found in the oceans; approximately 97.2%. The following are the percentages for each water source:

Despite the over abundance of rain we often receive, the atmosphere contains very little of the earth's total water supply. This demonstration can lead into water conservation awareness and to get the students to think about ways to save our drinking water. For more info visit EPA Water Sense

Live Weatherwise

Flash floods are the deadliest natural disaster in the world. They are caused by stationary or slow-moving thunderstorms that produce heavy rain over a small area.

Hilly and mountainous areas are especially vulnerable to flash floods, where steep terrain and narrow canyons can funnel heavy rain into small creeks and dry ravines, turning them into raging walls of water. Even on the prairie, normally-dry draws and low spots can fill with rushing water during very heavy rain.

Take time to develop a flood safety plan-for home, work, or school, and wherever you spend time during the summer. The National Weather Service has additional information about flood safety and a brochure "Floods and Flash Floods...The Awesome Power".

• Know the name of the county where you live and nearby rivers and streams. Keep a map so you know where storms that may cause flash flooding are.
• Determine if you are in a flood-prone area. If you are, know where to go if the water starts to rise. Have an escape route if you have to leave quickly.
• Make a safety kit containing: A flashlight and extra batteries, battery-powered weather radio receiver and commercial radio, extra food and water, first-aid supplies, canned food and a can opener, water (three gallons per person), extra clothing, and bedding. Don't forget special items for family members such as diapers, baby formula, prescription or essential medications, extra eyeglasses or hearing aids, and pet supplies.
• Know how and when to shut off utilities: Electricity, gas, and water.
• Seek sources for obtaining local warning information such as from cable TV or the NOAA Weather Radio.

At its core, the hydrologic cycle is water, as a liquid or solid, changing into water vapor (a gas) and back into a liquid or solid. This change of state of water occurs in the atmosphere and between the earth's surface and atmosphere.

This basic cycle is seen almost daily around the world in the formation and dissipation of clouds. When a cloud develops it is water vapor becoming a liquid. Conversely, when a cloud dissipates, liquid water changes state back into a gas.

The Ocean's Role

On a global scale, nearly all of the water in the water cycle is in the oceans. The oceans hold 96.5% of the earth's water and because of their size it may take thousands of years for a water molecule to move from the ocean to the atmosphere. This is in spite of an average 45 inches (114 cm) of water that evaporates from the ocean each year. (An additional 1% of salty water is also found in saltwater lakes and saline groundwater.)

The highest rate of evaporation from the oceans occurs in winter for both the Northern and Southern Hemispheres. The location of greatest evaporation is found on the east coasts of continents. This is due primarily to winter storms that move off the east coasts of continents which tend to have strong winds. These winds help carry water vapor away from its source thereby allowing more evaporation to take place.

The other factor is the warm ocean currents that move pole-ward along the east coasts of continents. The cold winter-time air masses that move over the water allow for large differences in air and sea temperatures so evaporation is also large. Then, when these differences in air and sea temperatures are combined with strong winds it makes evaporation in these regions very efficient.

Yet, of all evaporation that occurs over the oceans, a little over 90% of the moisture falls directly back into the sea as precipitation. And after spending upwards of a few thousand years in the ocean, a water molecule, on average, will only spend about nine days in the atmosphere before returning to earth. This is a very simple water cycle!

But over land, the water cycle can become quite complicated. The remaining 10% of moisture is transported over land and falls as precipitation from where it can travel a myriad of paths. If the precipitation falls as snow, it can remain frozen for a day or two then melt and flow into a river. Or the snow can become compacted and be locked up in a glacier for centuries.

Some water may infiltrate the soil or percolate into the groundwater. While most groundwater returns to the ocean, some groundwater can bubble up to the surface as a spring and evaporate back into the atmosphere, flow into a river, or even be captured and bottled for human consumption.

But remember, of all the water on the earth only 2.5% is fresh water and nearly all of that fresh water is locked up in glaciers and groundwater. Perhaps surprisingly, the atmosphere only contains about one-thousandths percent of all water on the earth.

The distribution of fresh water and estimation of the time a water molecule remains in various features, can be seen in the table (below). The Water Cycle chart (above ) shows additional sub-cycles contained within the greater cycle. .