KNOW YOUR H2O
KNOW YOUR H2O
Information to help you plan
We all know that water is essential to life. However, many times we take this important resource for
granted. We expect it to be clean and abundant, but we do not take the necessary precautions to protect
or conserve it. Without an abundant supply of good quality water, San Antonio, as well as the entire state
of Texas, could suffer an environmental and financial crisis in the future.
WATER IS…
 The only substance that occurs naturally in all three physical states (solid, liquid, and gas)
 A large portion of all living materials
 Odorless, tasteless, colorless
 Essential to life
 The most abundant, unique, and important substance on earth
EXACTLY WHERE IS WATER?
As you already know, water is essential to life on Earth. Water surrounds us. It is in the air as rain, ice,
snow, steam, and fog. It is in lakes, streams, rivers, oceans, and glaciers. Earth has so much water, it
has been given the nickname “the water planet”. But this water really isn’t new at all. In fact, at this very
moment, we have all the water we will ever have or ever have had. No new water is being manufactured.
This recycling process is called the hydrologic cycle or water cycle.
Water’s unique properties allow it to be a universal material. One of these special properties is its ability to
change states very easily. Water can be found in three forms: a liquid, a solid, and a gas. While water can
be found most often in its liquid form, it becomes a solid when the temperature drops below freezing at
32 F or 0 C and becomes a gas when the temperature rises to 212 F or 100 C. These forms play an
important role in the hydrologic cycle process.
The hydrologic cycle, or water cycle as it is also called, takes place in the hydrosphere, a region
containing all the water in the atmosphere and on the surface of the Earth. The process occurs through
five vital stages: Condensation, Precipitation, Runoff, Infiltration, and Evaporation/Transpiration.
Condensation- When the Earth’s air cools enough, water vapor condenses on particles in the air to form
clouds. Clouds are then moved across the globe by winds which spread water vapor across the planet.
Precipitation- As the clouds become warmer and are “heavy” with vapor, they release this moisture to
Earth in the form of precipitation, which can be snow, rain, hail or sleet.
Infiltration, Runoff, Evaporation/Transpiration- The next three stages occur simultaneously after
precipitation falls to the ground. Infiltration happens when precipitation seeps into the ground recharging
shallow water tables and deep aquifers. However, if precipitation occurs faster than it can infiltrate the
ground, it becomes runoff.
Runoff is precipitation that remains on the surface of the Earth flowing into streams, rivers and eventually
large bodies of water such as lakes or oceans.
Evaporation/Transpiration begins when the power of the sun (heat) changes the liquid water to a vapor
(gas). As the liquid heats, molecules are released and changed into a gas. The more heat that is applied
to water, the faster the process of evaporation takes place. Warm air rises up into the atmosphere and
becomes vapor.
1.
KNOW YOUR H2O
Transpiration occurs when plants release water vapor through their leaves and into the atmosphere. Once
the vapor enters the atmosphere, the entire hydrologic cycle begins again.
Condensation
Precipitation
Evaporation/
Transpiration
Runoff/Accumulation/
Collection
THE EARTH’S WATER USE
Water is the most abundant substance on Earth. Over 70% of the Earth’s surface is covered with water
making the world’s supply about 326 million cubic miles. It is estimated that if it were poured on the
United States, it would submerge the country to a depth of 90 miles. However, only a small portion of that
water supply is usable fresh water. Most of the water on Earth is salt water, which is found in the oceans
and seas. Salt water comprises over 97% of the water on the Earth. Just over two percent of the water
on the Earth is fresh water frozen in glaciers and the polar ice caps.
Less than one percent of the water on Earth is fresh ground water and fresh water lakes, rivers, and
streams that is usable for humans.
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KNOW YOUR H2O
WATER IS LIFE
Water is of major importance to all living things. In fact, water deprivation kills faster than lack of any other
nutrient. Without it, a person would be dead in about 5 days.
In some organisms, up to 90% of their body weight comes from water. Up to 60% of the human body is
water: the brain is composed of 70% water, blood is 82% water, and the lungs are nearly 90% water.
Humans also lose water through perspiration, respiration, and waste elimination.
Water is a lubricant and the presence of water in and
around body tissues helps defend the body against
shock. The brain, eyes, and spinal cord are among the
body’s most sensitive structures that depend on a
protective water layer. Water regulates body temperature.
Our health and well-being are dependent on keeping
body temperature within a very narrow range. Water in
the human body serves this function well. Evaporation of
water from the body surface also helps the body stay
cool. Sweat loss that occurs every day and night is barely
noticeable. People may lose up to a pint of water each
day through sweating. In hot, humid weather or during
exercise, increased sweating and losses are more visible.
There isn’t a “recommended daily allowance”
for water consumption. Part of the reason for
this is the difference in individuals related to
the climate in which you live, physical
activity, age, present physical condition, and
body size. Healthy adults require at least
eight to ten cups of water each day. Although
many times we drink milk, fruit juices, coffee,
tea, and sodas instead of water, our bodies
still are able to extract the water from these
sources through digestion and metabolism.
The most important thing to remember is that
proper hydration is extremely important to
maintain optimal health.
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KNOW YOUR H2O
WATER POLLUTION
Each time we use water, we change its quality by adding substances to it. These materials are such
things as municipal sewage, toxic chemicals, automotive oils, fertilizers, detergents, and pesticides.
Some materials, even in small quantities, can damage water quality to the point that makes it unusable. A
single quart of motor oil, for example, could pollute as much as 250,000 gallons of water.
Densely populated urban areas (like San Antonio), which are covered by impervious surfaces like streets,
sidewalks, roof tops, and buildings, increases the amount and decreases the quality of storm water runoff. The high concentrations of people in these areas tend to produce greater quantities and varieties of
pollutants. Think about your neighborhood for example. Have you ever considered what happens to the
fertilizers and insecticides that wash off your yard during a thunderstorm? When it rains, these types of
pollutants are washed into neighborhood gutters and storm drains which are not connected to any
wastewater treatment plant and therefore not treated. These urban pollutants flow through the storm drain
system and empty directly into our local rivers, creeks, and lakes. In San Antonio and Bexar County, all
rivers and creeks drain to the San Antonio River and eventually drain into the Gulf of Mexico. These
pollutants could therefore harm wildlife and fisheries and ruin recreational areas from here to the Texas
coast.
Water pollution is identified in two categories.
Point Source Pollution is contamination that
comes from a single, clearly identifiable
source, such as a pipe which discharges
material from a factory into a lake, stream,
river, bay, or other body of water. Point
source pollution is relatively easy to identify.
Non-point Source Pollution is more difficult to
identify. This is pollution which originates
over a broad area from a variety of causes.
Examples of non-point source pollution
include improper application of pesticides
and fertilizers, sediment from construction
sites, and petroleum-based products from
streets and parking lots. Non-point source
pollution usually originates from storm water
runoff.
WATERSHEDS
Watersheds are areas where water on the surface of the earth flows toward a water body including
creeks, lakes, rivers, or oceans. A ridge or other area of elevated land, called a divide, separates one
watershed from another. Streams on one side of the divide flow a different direction than streams on the
other side. Watersheds are important because scientists can study them in order to help determine how
much surface water might be available for a community’s needs.
Streams within a watershed form from rain water, runoff, snowmelt, and springs. As this water flows
over a watershed, it recharges (or fills) surface and ground-water supplies.
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KNOW YOUR H2O
GROUNDWATER
Groundwater is the part of precipitation that seeps down (or infiltrates) through the soil until it reaches rock
material that is saturated with water. Groundwater slowly moves underground, generally at a downward
angle (because of gravity), and may eventually seep into streams, lakes, and oceans.
The Edwards Aquifer: Our Local Groundwater Story
An aquifer is an underground area of rock, sand, gravel or soil that holds usable amounts of groundwater.
The Edwards Aquifer is a unique groundwater system. It is one of the greatest natural resources on Earth,
serving the diverse agricultural, industrial, recreational, and domestic needs of almost two million users in
south central Texas. Water from the Edwards Aquifer is the reason that 18th century Spanish
missionaries were able to establish footholds like the Alamo on the New World frontier. The Edwards
Aquifer is also the reason that San Antonio and many other cities in the surrounding region were able to
grow and prosper for over two centuries without developing surface water or other water resources.
The San Antonio section of the aquifer extends in a 180-mile arc-shaped curve from Brackettville in the
west to Kyle in the east.
The aquifer is divided into three hydrologic and geologic zones: the contributing zone (also referred to as
the drainage area or catchment area), the recharge zone and the artesian zone. The contributing zone
occurs on the Edwards Plateau, also called the Texas Hill Country. When it rains over the contributing
zone, the rainfall enters streams and rivers which then flows south toward the recharge zone.
Once the rainwater reaches the recharge zone, it flows over fractured limestone forcing the water to flow
underground and down into the aquifer. In the recharge zone, sedimentary limestone is exposed at the
surface and provides a pathway for water to be transported underground into the aquifer. Water that
recharges the aquifer comes from two primary sources: rain water that falls over the Hill Country and
surface water (such as streams, rivers, and creeks) that travel over the Hill country limestone and then
goes underground. Only about 3% of the recharge zone occurs within Bexar Counties boundaries.
The water is now in the artesian zone which is generally located south of the recharge zone and is the
area where the water is contained underground. In the artesian zone, the water in the Edwards Aquifer is
confined, both above and below, by impermeable rocks which can be thought of as “waterproof” layers.
The water flows underground through small cracks and holes in the limestone rock called a karst
formation. This karst area is formed by an erosion process that removes the calcium carbonate from the
above rocks through a chemical reaction. Above the surface it is characterized by sinkholes and caves
and below the surface, by underground drainage. Because the water is confined in this zone, it is under
pressure.
In a balanced system, the amount of water being removed from the aquifer does not exceed the amount
going in as recharge. There are two ways that water is removed from the aquifer. The first way is by
drilling wells into the aquifer and the second way is through natural spring flow. Flowing springs in this
area include the San Marcos Springs and Comal Springs in the northeast and San Antonio Springs and
San Pedro Springs in the southwest. The largest springs are in New Braunfels at Comal Springs and in
San Marcos at the San Marcos Springs.
No one really knows exactly how much water is in this aquifer, but it is generally agreed that if you took
the water out of the aquifer, you would be able to fill the state of Texas to about 1 foot in depth. Although
San Antonio receives 22-24 inches of rain a year, droughts in South Texas combined with increased
population growth has put a strain on this groundwater source.
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KNOW YOUR H2O
WATER CONSERVATION
On the average, every American uses about 100 gallons of water a day.
That makes daily water consumption in the U.S. alone over 372 billion
gallons per day. San Antonio is no different. Since our city is growing and
relies heavily on the Edwards Aquifer to receive our drinking water, that
makes us especially mindful about conserving water. Water we save is
water that we don’t have to buy. So it’s important we do everything we can
to decrease our water consumption.
A toilet, for instance, is the fixture that uses the most water daily in an
average household, usually around 26%. Old toilets can use from 3.5 to 7
gallons per flush. Low-volume flush toilets used in new construction or sold
at the hardware store today are 1.6 gallon capacity. This gets the job done
just as well, but with less water.
Did you know that a five-minute bath uses more water than a five-minute
shower? Baths can use up to 50 gallons of water whereas a shower with a
low flow showerhead would only use 10 gallons. Low flow showerheads can
save over 2 gallons per minute.
Outdoor usage accounts for about 60% of San Antonio’s water use during the summertime through
activities such as watering the lawn, washing the car, and spraying off the sidewalk.
We should all put voluntary restrictions on our water usage around the house. But in times of
drought, additional water restrictions may be needed to ensure that the aquifer remains at a safe
level.
WATER WORKS!
Wastewater Treatment
Much of the water used by homes, industries, and
businesses must be treated before it is released
back to the environment.
If the term "wastewater treatment" is confusing to
you, you might think of it as "sewage treatment."
Nature has an amazing ability to cope with small
amounts of water wastes and pollution, but it would
be overwhelmed if we didn't treat the billions of
gallons of wastewater and sewage produced every
day before releasing it back to the environment.
Treatment plants reduce pollutants in wastewater to
a level nature can handle.
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KNOW YOUR H2O
Wastewater is used water. It includes substances such as human waste, food scraps, oils, soaps, and
chemicals. In homes, this includes water from sinks, showers, bathtubs, toilets, washing machines, and
dishwashers. Businesses and industries also contribute their share of used water that must be cleaned.
Wastewater also includes storm runoff. Although some people assume that the rain that runs down the
street during a storm is fairly clean, it isn't. Harmful substances that wash off roads, parking lots, and
rooftops can harm our rivers and lakes. In San Antonio and many other cities however, this type of
wastewater never makes it to a treatment facility.
Why Treat Wastewater?
 Fisheries
Clean water is critical to plants and animals that live in water. This is important to the fishing industry,
sport fishing enthusiasts, and future generations.
 Wildlife Habitats
Our rivers and oceans waters teem with life that depends on shoreline, beaches and marshes. They are
critical habitats for hundreds of species of fish and other aquatic life. Migratory water birds use the areas
for resting and feeding.
 Recreation
Water is a great playground for us all. The scenic and recreational values of our waters are reasons many
people choose to live where they do. Visitors are drawn to water activities such as swimming, fishing,
boating, and picnicking.
 Health
If it is not properly cleaned, water can carry disease. Since we live, work, and play so close to water,
harmful bacteria have to be removed to make water safe.
Down the Main Drain
All of the clean water that comes into your house by one set of pipes leaves your house by another set of
pipes; clean water becomes wastewater. Wastewater comes from houses, schools, businesses, industry,
and storm runoff. Wastewater leaves these locations through gravitational forces and flows through
thousands of miles of underground sewer lines following the natural topography of watersheds.
SAWS currently uses four local watersheds (Central/Olmos Creek/San Antonio River, Leon Creek, Salado
Creek and Medio Creek) as natural transport mechanisms for its wastewater distribution system.
Finally, the wastewater reaches one of three wastewater treatment facilities located in south and west
Bexar County and the water recycling process then begins.
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KNOW YOUR H2O
Water Can Be Recycled
With the scarcity of water in some parts of the U.S. and with water conservation being so important today,
the reuse of treated wastewater is becoming more important. No, you don't have to worry about your
drinking water at home coming right from a sewage-treatment plant (although some communities are now
actively engaged in this). But treated wastewater is being used for certain purposes throughout Bexar
County. The use of recycled wastewater helps us in two ways:
1. Recycled water can supply needed water for some purposes
2. Recycled wastewater frees up fresh water that can be used somewhere else, such as for drinking
water
So, what exactly is recycled wastewater used for? A lot of it goes toward watering golf courses and
landscaping alongside public roads, etc. Some industries, such as power-generation plants can use
recycled wastewater. A lot of water is needed to cool power-generation equipment, and using wastewater
for this purposes means that the facility won't have to use higher-quality water that is best used
somewhere else.
LIQUID VOCABULARY
Aquifer-Porous, water bearing layer of sand, gravel
and rock below the Earth’s surface that acts as a
reservoir for groundwater.
Artesian Well-A well in which the water comes from
an aquifer that is under pressure. One type of artesian
well is a flowing well where water just flows or bubbles
out of the ground without being pumped.
Condensation-The changing of a gas or vapor into a
liquid.
Conserve-To preserve and protect a natural resource from wasteful use.
Contaminate-An impurity, that causes air, soil, or water to be harmful to human health or the
environment.
Deposit-Something left behind by moving water, as sand or mud.
Drought-A long period of time without a sufficient amount of rain.
Erosion-The wearing away of the Earth’s surface by running water, wind, ice, or other geological agents
by which material is removed from the Earth’s surface.
Evaporation-To convert or change into a vapor with the application of heat.
Gas-A state of matter in which molecules do not touch. Gases expand freely to fill their container.
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KNOW YOUR H2O
Groundwater-The supply of fresh water beneath the Earth’s surface, which is often used for supplying
wells and springs.
Hazardous Chemicals-Chemical compounds that are dangerous to human health and or the
environment.
Ice-A solid form of water.
Impermeable-Material that will not allow water to pass through it.
Infiltration-The gradual downward flow of water from the surface into soil materials.
Karst-A topography formed over limestone, dolomite, or gypsum and characterized by sinkholes, caves,
and underground drainage.
Lakes-An inland body of water, usually fresh water, formed by glaciers, river drainage, etc., larger than a
pool or pond.
Land use-How a certain area of land is utilized (e.g. forestry, agriculture, urban, industry).
Liquids-A state of matter, neither gas nor solid, that flows and takes the shape of its container.
Matter-Anything which is solid, liquid, or gas and has mass.
National Pollutant Discharge Elimination System (NPDES)- Part of the Clean Water Act requiring
municipal and industrial wastewater treatment facilities to obtain permits which specify the types and
amounts of pollutants that may be discharged into water bodies.
Non-permeable surfaces-Surfaces which will not allow water to penetrate, such as sidewalks and
parking lots.
Nonpoint source pollution-Pollution that cannot be traced to a single point, because it comes from
many individual places or a widespread area.
Oceans-The great bodies of salt water which cover more than two-thirds of the earth’s surface.
Pesticide-Any chemical or biological agent that kills plant or animal pests; herbicides, insecticides,
fungicides, etc. are all pesticides.
Point source pollution-Pollution that can be traced to a single point source, such as a pipe or culvert.
Pollution-An unwanted change in air, water, or soil that negatively affects the health and survival of
humans and other organisms.
Precipitation-A deposit on the earth of hail, rain, mist, sleet, or snow. It is the common process by which
atmospheric water becomes surface or subsurface water.
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KNOW YOUR H2O
Puddle-A small pool of water, usually a few inches in depth and from several inches to several feet in its
greatest dimension.
Rain-Water drops which fall to the earth from the air.
Recharge-Replenish a water body or an aquifer with water.
Recharge area-An area where water flows into the earth to re-supply a water body or an aquifer.
River-A natural stream of water of considerable volume.
Runoff-Water (originating as precipitation) that flows across surfaces rather than soaking in; eventually
enters a water body; may pick up and carry a variety of pollutants.
Saturated zone-Underground layer in which every available space is filled with water.
Sediment-Solid material that has been moved from its original site by water and has been deposited on
the land or in the sea.
Sinkhole-A natural depression in a land surface connected to a subterranean passage, generally
occurring in limestone regions and formed by solution or by collapse of a cavern roof.
Solid-A state of matter, neither a liquid or gas. The solid state of water is ice.
Solvent-A liquid capable of dissolving another substance (e.g. paint thinner, mineral spirits, and water).
Spring-A place where water flows naturally from underground in the aquifer to the surface.
Storm water Runoff-Surface water runoff that flows into storm sewers.
Surface Water-Water that is stored on the earth’s surface.
Transpiration-The process by which water vapor escapes from a living plant, principally through the
leaves, and enters the atmosphere.
Treatment Plant-Facility for cleaning and treating fresh water for drinking, or cleaning and treating
wastewater before discharging into a water body.
Water-The liquid that descends from the clouds as rain; forms streams, lakes, and seas and is a major
constituent of all living matter; is an odorless, tasteless, colorless, and a very slightly compressible liquid.
Water Cycle-Continuous movement of water from the oceans and fresh water sources to the air and land
and then back to the oceans.
Watershed-Land area from which water drains to a particular surface water body.
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