(1) The Hydrologic Cycle - SAHRA

(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?


Earth’s Pools of Water


Earth’s Pools of WaterWhat is the residence time of these pools?

Residence time =

Volume (mass)/flux (in-out)

11 days

~3000 years

Days to millions of years


Where does your drinking water come from?



(2) What’s in the Water?

What is water made of?

Smallest unit of water = water molecule

3 phases of water: water vapor, liquid water, and ice


What is water made of?

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)

Water is a colorless, odorless liquid by itself


Why is water a good solvent?


Chemical bonding of the water molecule makes it a good solvent - polar compound - can attach to positive and negatively charged molecules

Ca2+

SO42-


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)



Major Ion Chemistry of Different Water Types?

Stream waters, Valles Caldera Preserve, NM

San Pedro Basin groundwater

Seawater

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

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

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


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.



Is Bottled Water any Better for You than Tap Water?

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).

Barzilay et al. (1999)

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.


Is Bottled Water any Better for You than Tap Water?

Major difference: is TASTE.Chlorine added for disinfection in municipal water suppliesIron 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.

Barzilay et al. (1999)J. McIntosh UA-HWR (2012)

(3) Water Quality Indicators


Major Water Quality Indicators

Dissolved Oxygen

Temperature

pH

Organic substances (Biological Oxygen Demand)

Inorganic substances (metals, sediments, nitrates, water hardness)

Turbidity

Nutrients

Toxics

Microorganisms

Vigil (2003) Clean WaterJ. McIntosh UA-HWR (2012)

Dissolved Oxygen & Temperature

Vigil (2003) Clean Water

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.

Oxygen is more soluble in colder water.

Would you expect DO to be higher or lower in cold water?




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




Industrial discharge to surface waters typically needs to be cooled…

Leaving trees around streams during clear cutting to enhance shading.


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


Organic substances

Organic compounds contain CARBONand include: human wastes, animal wastes, food processing wastes, and hydrocarbon (petroleum)-derived substances

Biodegradation of organic substances in water removes oxygen - decreasing water quality


What are organic compounds?

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.


Inorganic substances

Rocks and minerals; metals; and solids; nitrogen and phosphorus


(1) Hard Water: high concentrations of calcium and magnesium

Classification mg/LSoft 0-17Slightly hard 17-60Moderately hard 60-120Hard 120-180Very hard >180


Inorganic substances


(2) Metals - including arsenic, lead, chromium, mercury


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?


Nutrients

Essential elements (C,N,P) needed for growth; but can be a contaminant in high concentrations (e.g. eutrophication of surface waters)


Toxics

Substances that can cause death and deformation of organisms in waterExamples include: Dioxins, TCE, petroleum products, pesticides & herbicides


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.


QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Waterborne disease outbreaks


(4) Water Quality Regulations & Standards


Clean Water Act

Main Objective: “Restore and maintain the chemical, physical, and biologicalintegrity 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


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.


EPA Regulated Contaminants & MCLs


http://water.epa.gov/drink/contaminants/index.cfm



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.




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.


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

A poor Environmental Impact Statement or Assessment (potentially bad for the environment) doesn’t necessarily stop projects from going forward.

If a project receives a poor environmental review, does that stop the project?


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.


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.


(1) The Hydrologic Cycle - SAHRA

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