Water
Water
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Water is one of the most important substances on Earth because it is essential to life. The human body contains about 50 - 65% water, by weight; although you can live for weeks without food, you can only survive a few days without water.
Despite the importance of water, more than a billion people in low and middle-income countries, and an additional 50 million people in high-income countries lack access to safe drinking water. Water that is available is often contaminated and unfit for drinking. One reason for this problem is that in the developing world, 90% of urban sewage is discharged untreated into rivers, lakes, and coastal waterways. Approximately 900 million people suffer from water-related diarrheal illnesses each year. Millions more suffer from water-related diseases such as cholera, elephantiasis and hookworm.
Without access to safe drinking water, people cannot lead healthy, productive lives.
Water is also geologically important because of its role in weathering, erosion, and transportation and deposition of sediment. In its frozen state as glacial ice, water also reshapes the land through erosion and deposition. Water is a powerful geologic agent with the ability to carve deep canyons, and dissolve limestone to produce caverns and sinkholes.
In some cases, we have too much water. In terms of loss of life, floods are the most devastating of all geologic agents.
Almost 80% of the Earth's surface is covered by water.
However the water is not evenly distributed, and most of it is unsuitable for drinking.
Of the total volume water on the Earth (1.36 billion km3, or 326 million mi3):
We can use less than one percent of the water on Earth for drinking and personal hygiene. We also use this fresh water for agriculture, fisheries, transportation, heating and cooling, manufacturing, and many other purposes.
Unfortunately, unless we use our freshwater wisely, rivers, lakes, and groundwater can become depleted or polluted, and unavailable or unsuitable for life.
Earth's water is always in movement. TheWater Cycle (sometiems called the Hydrologic Cycle) describes the continuous movement of water on, above, and below the surface of the Earth. Since the water cycle is truly a "cycle," there is no beginning or end. Water can change states among liquid, vapor, and ice at various places in the water cycle, with these processes happening in the blink of an eye and over millions of years.
The Sun powers the Water Cycle.
The Water Cycle. Source: U. S. Geological Survey.
The cycling of water in and out of the atmosphere plays an important role in determining climatic patterns. Water evaporates from the surface of the Earth, rises and cools, condenses into rain or snow, and falls again to the surface. The water falling on land collects in rivers and lakes, soil, and porous layers of rock, and much of it flows back into the ocean.
Although the balance of water on Earth remains fairly constant over time, individual water molecules move around quickly. The water you drank yesterday may have fallen as rain half-way around the world last year, may have been part of the glacial ice sheet that covered much of North America 18,000 years ago, may have helped carve the Grand Canyon, or may have passed through a dinosaur 100 million years ago.
The Water Cycle is powered by solar energy and gravity.
The following processes are part of the Water Cycle. See if you can locate them on the picture above.
Sources of drinking water include the following:
Surface water may become contaminated by chemicals or disease-causing organisms from animal and human waste as a result of surface runoff, waste disposal directly into streams, or acid rain. In the United States, roughly 34 billion gallons of water are treated each day.
Groundwater is typically potable, but surface water needs to be purified.
Approximately 15% of the population in the U.S. obtains water from an individually owned well, spring, or cistern.
Ground water can become contaminated by infiltration from the surface, injection of contaminants, or from naturally-occurring substances in the soil or rock through which it flows. Ground water is particularly vulnerable to nitrate contamination, especially in rural agricultural areas (from fertilizer) or areas with large numbers of septic tanks.
In Georgia, on average, water use per person is 168 gallons per day. This includes water used for residential, commercial and industrial purposes (but not including agricultural uses.)
Only a small portion of drinking water is actually used for drinking (generally less than 1 gallon per day). It is recommended that you drink at least 2 quarts of water per day. Dishwashers use about 15 gallons, whereas handwashing dishes uses about 20 gallons. Washing machines use about 30 gallons per load. Toilets use 5 - 7 gallons per flush. A shower uses 5 to 10 gallons per minute, for a total of about 35 to 50 gallons.
How do you compare? The next time you shower, plug up the tub and see how much water you are actually using. A tub holds about 36 gallons if filled to the brim. The major water use is typically watering the lawn. Watering the lawn at 5 - 10 gallons per minute will use 300 gallons in a half hour!
A public water system draws water from a source, treats it if needed, and distributes it to homes, businesses, industry, etc.
After water is used, it typically goes down the drain, or soaks into the ground.
When wastewater leaves the home through a pipe (drain or toilet) the water goes to the sewer or to a septic system.
If the wastewater goes into a sewer system, it travels to a wastewater treatment plant, where it is treated, and released into a river, or reused.
If the wastewater goes to a septic system, it enters a septic tank (where some contaminants settle out and are stored in the tank)
and then to a drainfield where the wastewater percolates through the soil and into the ground water.
Sometimes drinking water contains pathogens or disease-causing organisms and viruses.
Types of pathogens in water include:
In June 1998, an outbreak of Escherichia coli O157:H7 occurred at White Water, a water park in Cobb County, Georgia, most likely caused by fecal contamination from a diaper. The original source of contamination was linked to contaminated beef that had been served at a northeast Georgia school. Illness occurred 2-10 days after exposure at the waterpark, and 26 cases were proven by bacterial culture. Seven people developed hemolytic uremic syndrome (HUS), and one child died.
In 1987, an outbreak of Cryptosporidium sickened as many as 15,000 residents of Carroll County, GA with diarrhea, and forced residents to boil their drinking water for a month. A similar problem occurred in Milwaukee in 1993, affecting 800,000 residents. The source of the Georgia outbreak was believed to be drainage of animal waste from stockyards. Cryptosporidium is commonly found in lakes and rivers. The reproductive cysts of the organism can survive under a wide range of environmental conditions, and are resistant to chlorination at water treatment plants and in swimming pools. Boiling drinking water is the best method of killing Cryptosporidium and other waterborne pathogens. Water should be boiled for at least one minute, and may then be refrigerated in a clean bottle with a lid.
Bottled water may contain many types of minerals. Bottled water is not necessarily safer than tap water.
Water conservation http://www.epa.gov/owm/water-efficiency/index.htm
Drinking water for kids - classroom activities http://www.epa.gov/safewater/kids/exper.html Water games and online activities http://www.epa.gov/safewater/kids/games.html
Georgia Department of Natural Resources Water Conservation Program
Water conservation http://www.epa.gov/owm/water-efficiency/index.htm Visit this website to learn how to conserve water and use it effectively.
As part of the water cycle, when it rains, some of the water infiltrates or soaks into the ground. Some of the water is held in the soil because it clings to the soil particles because of molecular attraction. There is both air and water in the pore spaces in the soil. This is the unsaturated zone. Water may evaporate from the soil or be used by plants. Excess water penetrates downward until it reaches the water table. Below the water table, all of the pore spaces are filled with water (saturated zone).
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Click image for a larger view. Source: U.S. Geological Survey
http://pubs.usgs.gov/gip/gw/ .
The water table is the top of the saturated zone.
The water table is not flat. It mimics the topography, but is more subdued. It stands somewhat higher under hills, and lower under valleys.
Where the water table intersects (or lies above) the ground surface, springs. lakes, swamps, or rivers are present. In humid areas, groundwater movement supplies water to streams and rivers.
If a well is drilled, the water level in the well is at the water table.
Think about when you went to the seashore and dug a hole in the sand near the sea. Remember how the water came up in the hole? The surface of the water in the hole was the water table.
The level of the water table fluctuates with droughts.
If water is withdrawn from a well, the water table is lowered in the immediate vicinity of the well. The lowered surface of the water table around a well forms a conical depression in the water table. It is called the cone of depression.
If significant quantities of water are withdrawn from a well, the cone of depression may be so large that it affects the water level of other wells nearby.
An aquifer is a water-bearing rock. Aquifers have high porosity and high permeability. Sandstones and gravels make good aquifers.
Aquicludes are water-excluding rocks. They have little or no porosity or permeability. Shales make good aquicludes.
Note that some impermeable rock types may serve as aquifers if they are highly jointed. Water may be in the joints or cracks in the rock.
The place in which water enters an aquifer is called the recharge area.
An average well in Georgia yields about 20 gallons per minute (gpm). With careful geologic study (such as lineament mapping), yield can be increased to 100 - 300 gpm. A few new wells in Cobb County (Piedmont region) yield 500-550 gpm. And in most cases, the groundwater is pure enough for drinking, but the surface waters must be treated (purified) before drinking. (Information from the State Geologist, William McLemore, May 30, 1996 at the Atlanta Geological Society meeting).
The Atlanta Journal-Constitution (Sunday Feb. 22, 1998) reported the following in its column, "EarthWeek - A Diary of the Planet" by Steve Newman: "Mexico's capital city is sinking at a rate of up to 18 inches per year because of the massive pumping of groundwater to supply the megalopolis of nearly 20 million people. The National Water Commission reported that the city has sunk by 33 feet because of the process this century. "If the current rate of drainage continues, not only will it affect the quality and quantity of underground water, it would also cause social and economic problems for the population", the report said."
Lowering the water table through pumping may lead to an increase in sinkhole formation in areas underlain by limestone. Examples of this can be seen in Shelby Co. Alabama (just south of Birmingham) and in northwestern Georgia near Fairmount and Kingston, GA where pumping in limestone quarries has led to the formation of sinkholes in the cone of depression.
The discharge of a river or stream is defined as the amount of water flowing past a point in a given unit of time.
Measured in VOLUME/TIME (gal/min, m3/sec, or ft3/sec).
If you have a stream nearby, you can measure the discharge. Calculate the cross-sectional area of stream of the stream (depth times width), and multiply this by the velocity, which you can measure by timing how long it takes a float to flow over a measured distance (such as 50 ft).
Urbanization leads to:
As a result, there tends to be:
Potholes, Great Smoky Mountains National Park, Tennessee
These streams are very sinuous, and tend to migrate back and forth across the floodplain (or meander), over time. The word "meander" comes from the name of a sinuous river in Turkey, named the Menderes.
A meandering stream.
These streams have lots of lenticular-shaped in-channel bars. The stream channel bifurcates around these bars, and follows a pattern resembling braided hair.
Flood = any high flow of surface waters that overtops normal confinements or covers land normally dry
Types of floods:
Floods are the most devastating of all geologic agents - exceeded only by plagues, world wars and the Holocaust in loss of life.
Sites of worst floods - China's rivers
Larger figures include deaths from flood-induced famine, water-born diseases (cholera)
Note that levees are built up to prevent flooding, but may actually lead to more severe flooding.
Scenario:
In the photos below, note that the level of water in the river is higer than the level of the surrounding land (floodplain) on the other side of the levee.
Levee in New Orleans. Note the water level in the channel is well above the level of the surrounding land.
Atop the Mississippi River Delta in New Orleans.
Note the river level is approximately the same as the bottom of the rooftops visible at left.
Floodwall and flood gate on the top of the Mississippi River levee in New Orleans, beside the Jackson Brewery.
When river levels rise, the brown metal gate (center), rolls to the right to block flood waters.
Note the railroad tracks also on the levee.
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Page created by Pamela J.W. Gore
Georgia Perimeter College,
Clarkston, GA
Page created March 26, 2005
Updated email and facstaff, August 23, 2008