(1) The Hydrologic Cycle
J. McIntosh UA-HWR (2012)
What are the major pools
(reservoirs) of water on EARTH?
More than enough water on our
planet to sustain life. Why then
do we have water shortages?
And, why are we concerned
about running out of water?
J. McIntosh UA-HWR (2012)
Earth’s Pools of Water
J. McIntosh UA-HWR (2012)
Earth’s Pools of Water
What is the residence time of these pools?
~3000 years
11 days
Residence time =
Volume (mass)/flux (in-out)
J. McIntosh UA-HWR (2012)
Days to
millions of
years
Where does your drinking water come from?
J. McIntosh UA-HWR (2012)
(2) What’s in the Water?
J. McIntosh UA-HWR (2012)
What is water made of?
Smallest unit of water = water molecule
3 phases of water: water vapor, liquid water, and ice
J. McIntosh UA-HWR (2012)
What is water made of?
Water is a colorless, odorless liquid by itself
It’s the things dissolved in water that give is its taste, color, odor, density, and
ability to dissolve substances
“Water also consists of the materials dissolved or suspended in it, such as salts,
minerals, and other dissolved substances, plus soil particles, debris, and other
suspended solids. Water is alive. It contains small plants, animals, and microscopic
organisms.”
Vigil, Kenneth M..; Clean Water : An Introduction to Water Quality and Water Pollution Control (2003)
J. McIntosh UA-HWR (2012)
Why is water a good solvent?
SO42Ca2+
Chemical bonding of the water molecule makes it a good solvent - polar compound
- can attach to positive and negatively charged molecules
Vigil, Kenneth M..; Clean Water : An Introduction to Water Quality and Water Pollution Control (2003)
J. McIntosh UA-HWR (2012)
Why is water a good solvent?
Almost all solids, liquids, and gases placed
in water will dissolve to some extent
As water passes over rocks, or through soils
and bedrock, it can dissolve minerals, picking
up dissolved constituents (e.g. Ca, Fe, K, Na,
Cl, SO4)
Some of the substances dissolved in water,
or transported by water, can lower its water
quality (e.g. arsenic, lead, nitrates, E Coli),
while some substances improve water quality
(e.g. oxygen)
Vigil, Kenneth M..; Clean Water : An Introduction to Water Quality and Water Pollution Control (2003)
J. McIntosh UA-HWR (2012)
Major Ion Chemistry of Different Water Types?
Stream waters, Valles Caldera Preserve, NM
16.0 mg/L silica (Si)
7.3 mg/L sodium (Na)
5.9 mg/L calcium (Ca)
1.1 mg/L magnesium (Mg)
9.0 mg/L bicarbonate (HCO3)
1.7 mg/L chloride (Cl)
1.7 mg/L sulfate (SO4)
TDS = 42.7 mg/L
San Pedro Basin groundwater
12.3 mg/L sodium (Na)
51.5 mg/L calcium (Ca)
4.2 mg/L magnesium (Mg)
171 mg/L bicarbonate (HCO3)
5.5 mg/L chloride (Cl)
5.0 mg/L sulfate (SO4)
TDS = 249.5 mg/L
Seawater 10,700 mg/L sodium (Na)
420 mg/L calcium (Ca)
1,300 mg/L magnesium (Mg)
145 mg/L bicarbonate (HCO3)
19,250 mg/L chloride (Cl)
2,700 mg/L sulfate (SO4)
TDS = 35,000 mg/L
J. McIntosh UA-HWR (2012)
Concentration units of constituents in water
Parts per million (ppm) - think of a container filled with a million marbles of equal
size and weight. If a reported value (of arsenic for example) is 10 ppm, then 10 out
of 100 million marbles are arsenic atoms, while the rest of the marbles are water.
Milligrams per liter (mg/L) - concentration of substances in water expressed in
terms of mass (weight) of the substance found in one liter of water. For example,
10 ppm is the maximum contaminant level of arsenic in drinking water.
In most cases…ppm = mg/L…because one liter of water weighs approximately
one million milligrams.
Vigil, Kenneth M..; Clean Water : An Introduction to Water Quality and Water Pollution Control (2003)
J. McIntosh UA-HWR (2012)
Is Bottled Water any Better for You than Tap Water?
Bottom Line: In most cases, bottled water is not any better for your health
than tap water. Bottled water is regulated by the FDA, while municipal water
supplies are regulated by the EPA.
Exceptions: immuno-compromised people (need water with NO TRACE of
parasites/bacteria); osteoporosis prevention (need Ca and Mg, although most tap
water contains Ca and Mg); private well water concerns (e.g. arsenic, fluoride,
nitrates).
J. McIntosh UA-HWR (2012)
Barzilay et al. (1999)
Is Bottled Water any Better for You than Tap Water?
Major difference: is TASTE.
Chlorine added for disinfection in municipal water supplies
Iron from old pipes (rust staining on bath tubs)
Water picks up (dissolves) minerals as it percolates through geologic materials.
Waters in different geologic environments have different dissolved mineral contents,
or total dissolved solids (TDS).
Most people like 30-100 parts per million (mg/L) of total dissolved solids (TDS) in
their water.
Tucson water averages ~200 to 650 mg/L TDS.
J. McIntosh UA-HWR (2012)
Barzilay et al. (1999)
(3) Water Quality Indicators
J. McIntosh UA-HWR (2012)
Major Water Quality Indicators
Dissolved Oxygen
Temperature
pH
Organic substances (Biological Oxygen Demand)
Inorganic substances (metals, sediments, nitrates, water hardness)
Turbidity
Nutrients
Toxics
Microorganisms
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Dissolved Oxygen & Temperature
Fish and most other aquatic organisms need oxygen to survive. They use
oxygen for respiration, just like humans.
Most cold water fish (e.g. trout and salmon) prefer ~8-12 ppm of dissolved
oxygen (DO), and temperatures from ~34 to 59 oF.
Would you expect
DO to be higher or
lower in cold water?
Oxygen is more soluble in
colder water.
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Dissolved Oxygen & Temperature
Fast flowing rivers - typically contain more dissolved oxygen; riffles/whitewater
stretches help increase DO.
Slow flowing rivers - stagnant waters typically contain lower DO because they
don’t rapidly mix with the air along their course
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Dissolved Oxygen & Temperature
Industrial discharge to
surface waters typically
needs to be cooled…
Leaving trees
around streams
during clear cutting
to enhance
shading.
Vigil (2003) Clean Water
J. McIntosh UA-HWR (2012)
pH
pH = -log (aH+)
Wastewater that is
acidic or basic must
be treated before
being discharged to
streams
Most natural streams
Acid mine drainage;
sulfur hot springs
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Organic substances
What are organic compounds?
Organic compounds contain CARBON
and include: human wastes, animal
wastes, food processing wastes, and
hydrocarbon (petroleum)-derived
substances
Biodegradation of organic substances
in water removes oxygen - decreasing
water quality
How do we quickly measure
organics in water?
Biological oxygen demand (BOD) - seeing how quickly oxygen is removed in a
water sample gives you an idea of how much organic matter was present.
Vigil (2003) Clean Water
J. McIntosh UA-HWR (2012)
Inorganic substances
Rocks and minerals; metals; and solids; nitrogen and phosphorus
(1) Hard Water: high concentrations of calcium and magnesium
Classification
Soft
Slightly hard
Moderately hard
Hard
Very hard
J. McIntosh UA-HWR (2012)
mg/L
0-17
17-60
60-120
120-180
>180
Vigil (2003) Clean Water
Inorganic substances
(2) Metals - including arsenic, lead, chromium, mercury
Vigil (2003) Clean Water
J. McIntosh UA-HWR (2012)
Turbidity
Measurement of how cloudy the water is (aka, sediment load)
Turbidity can harm fish, as it reduces visibility and can be abrasive to their gills
How do we measure turbidity?
(1) Total suspended solids (TSS) - collect any solid materials on filter paper
and weigh.
(2) Total dissolved solids (TDS) - after filtering water sample, and drying,
determine much solid material remains?
If you added 500 mg of salt and 500 mg of pepper to 1L of
water, what would the TSS and TDS values be?
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Nutrients
Essential elements (C,N,P) needed for growth; but can be a contaminant in high
concentrations (e.g. eutrophication of surface waters)
Vigil (2003) Clean Water
J. McIntosh UA-HWR (2012)
Toxics
Substances that can cause death and deformation of organisms in water
Examples include: Dioxins, TCE, petroleum products, pesticides & herbicides
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Microorganisms
1 gallon of river water may contain more than 1 million bacteria and >10,000 algae.
Bacteria in water can cause dysentery,
cholera, typhoid, etc.
Viruses in water can cause small pox,
influenza, yellow fever, etc.
Vigil (2003) Clean Water
J. McIntosh UA-HWR (2012)
Waterborne disease outbreaks
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
J. McIntosh UA-HWR (2012)
(4) Water Quality Regulations & Standards
J. McIntosh UA-HWR (2012)
Clean Water Act
Main Objective: “Restore and maintain the chemical, physical, and biological
integrity of the Nation’s waters”
“The Clean Water Act (CWA) establishes the basic structure for regulating discharges of pollutants into the waters of the
United States and regulating quality standards for surface waters. The basis of the CWA was enacted in 1948 and was
called the Federal Water Pollution Control Act, but the Act was significantly reorganized and expanded in 1972. "Clean
Water Act" became the Act's common name with amendments in 1977.
Under the CWA, EPA has implemented pollution control programs such as setting wastewater standards for industry. We
have also set water quality standards for all contaminants in surface waters.
The CWA made it unlawful to discharge any pollutant from a point source into navigable waters, unless a permit was
obtained. EPA's National Pollutant Discharge Elimination System (NPDES) permit program controls discharges. Point
sources are discrete conveyances such as pipes or man-made ditches. Individual homes that are connected to a
municipal system, use a septic system, or do not have a surface discharge do not need an NPDES permit; however,
industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface water.”
EPA website
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Safe Drinking Water Act
Main Objective: Protect our drinking water supplies
Defines the maximum contaminant levels (MCLs) for: inorganic substances (e.g.
nitrates, metals); organic substances (e.g. benzene); and microorganisms (E. Coli).
EPA sets contaminant levels after reviewing scientific findings on toxicity and
evaluating public comment.
Water is considered safe to drink if concentrations of regulated contaminants (112
substances as of 1995) are below MCLs.
Can MCLs be refined (changed)?
Yes; EPA modifies MCLs as necessary - with new/better scientific information.
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
EPA Regulated Contaminants & MCLs
http://water.epa.gov/drink/contaminants/index.cfm
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Safe Drinking Water Act
Surface water and groundwater sources of drinking water are regulated differently.
Surface water sources generally have more extensive treatment requirements.
Surface water typically has to be filtered and disinfected before sending to
consumers to use as drinking water, while groundwater may only need to be
disinfected.
Vigil (2003) Clean Water
J. McIntosh UA-HWR (2012)
Safe Drinking Water Act
Water distribution systems are also regulated - old lead or copper pipes may be a
source of contamination.
Drinking water providers must notify the public (consumers) if there’s been a
violation of contaminant levels in the water supply.
Statement from Tucson Water (Municipal Water Supplier): “As a public water
provider, Tucson Water is regulated under the Safe Drinking Water Act, and all
drinking water must meet standards set by the US EPA, the Arizona Department of
Environmental Quality, and local ordinance.
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
National Environmental Policy Act
Main Objective: Protection of the whole environment - air, land, water, and life - by
“evaluating the environmental impacts of all activities sponsored by the federal
government.”
Any project that receives federal funding or federal interest (?) must complete
environmental reviews of the environmental impact of the proposed project.
(1) Environmental Assessment - small environmental effects anticipated
(2) Environmental Impact Statement - major environmental effects anticipated
If a project receives a poor environmental review, does that
stop the project?
A poor Environmental Impact Statement or Assessment (potentially bad for the
environment) doesn’t necessarily stop projects from going forward.
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water
Humpback Chub - AZ Endangered Species
 A lot of $$ and effort has gone into trying
to restore humpback chub habitat in the
Colorado River System by:
(1) modifying releases from Glen Canyon
Dam
(2) Creating artificial floods to replicate
historic conditions to the Colorado R.
(3) Removal of non-native predators, such as
rainbow trout
(4) Transplanting fish to tributaries
Number of humpback chub has gone up significantly in the Grand Canyon, but
it’s not clear why yet. Removal of predators may have helped, but there was also
a drought, which lowered the level of Lake Powell, causing water in the Colorado
River below Glen Canyon Dam to be much warmer than normal, promoting
reproduction.
J. McIntosh UA-HWR (2012)
Superfund Act
Main Objective: help prevent hazardous waste from damaging the environment.
Established in 1980 by the US Congress in response to abandoned or uncontrolled
hazardous waste sites like Love Canal.
Superfund Act includes programs for finding abandoned hazardous waste sites,
evaluating levels and types of contamination, and cleaning up the sites.
J. McIntosh UA-HWR (2012)
Vigil (2003) Clean Water