GSC1620 Chapter 11

Resources Overview and Water as a Resource

Resources (Background)

Earth resource – any valuable or useful commodity extracted from the Earth

Resources can be classified into various categories including: reserves, subeconomic resources, hypothetical resources, and speculative resources

Reserves – identified resources that are profitable to extract

Resources

Subeconomic resources – identified resources that are currently unprofitable to remove

Note: the classification of resources as reserves or subeconomic resources can change if the commodity price fluctuates significantly

Resources

Hypothetical Resources – resources hypothesized to exist because resources of that type have been found in the same general area and geological setting (gold “rush” mentality)

Speculative Resources – resources that are speculated to exist even though resources of that type haven’t been found in that area (see review figure)

Resources

Resources can also be classified as renewable and nonrenewable

Renewable resources are replaceable on a human time scale while nonrenewable resources are not

What is an example of a renewable and a nonrenewable resource?

Water as a Resource

Water as a Resource

Obviously no society can prosper without a reliable source of fresh water

Fresh, potable water has become a precious commodity in many parts of the world, here in the U.S. there are many legal battles raging, especially in the West, over water usage rights

Water as a Resource

Remember, the surface and subsurface waters of Earth are part of the hydrologic cycle (see figure)

We’ll initially focus on groundwaters since they constitute such a large percentage of our liquid freshwater resource (see figures)

Hydrologic cycle – powered by solar energy, the continual circulation of Earth’s waterthrough the atmospheric, surface, and subsurface reservoirs.

Groundwaters constituteabout 95% of Earth’s liquid freshwater resources!

About half of the US population relieson groundwater for drinking water!

Groundwater

The origin of groundwater is water that infiltrates the surface; however, not all subsurface water is termed groundwater

Groundwater is defined as subsurface water present in the saturated zone - here all the pore spaces between adjacent rock and sediment particles are saturated with water (see figure)

Groundwater

Groundwater moves due to the influence of gravity and the pressure from the weight of the overlying rock and sediment (squeezed sponge analogy)

Therefore, groundwater moves toward zones of lower pressure (i.e., the surface) (see slides)

Groundwater

As you’re seeing the groundwater and surface water systems (streams, lakes, wetlands) are typically intimately connected

Today, many scientists are advising that we consider these as one resource system

Why? Think of the practical and environmental applications when viewing the next slide.

Oakland PressJune 12, 2005

Brochure distributed in 2005 by the Brandon TownshipPhase II Stormwater Management Education Group

OaklandPress 7/26/07

Future Concern?

Groundwater

Significant quantities of groundwater are found only in sediments or rocks that are sufficiently porous and permeable (How would you define these terms?)

Porosity – the percentage of void (open) space a substance contains

Permeability – a measure of how readily a substance transmits fluids

Groundwater

Aquifers - rock or sediment bodies that absorb and transmit water very effectively

Aquitards – rock or sediment bodies with properties between those of an aquifer and aquiclude

See the following table and try to discern the best aquifer material

Groundwater Accumulation

Sediments like sands and gravels (which typically underlie the surface soils in southeast MI to maximum depths of 400 ft) typically make good aquifers

~97% of Oakland County wells terminate into sand/gravel aquifers

Groundwater Accumulation

Rocks like limestone and poorly cemented sandstones typically make good aquifers

Clay sediments, sedimentary rocks like shale and nearly all igneous and metamorphic rocks are aquicludes except under rare circumstances (see slides)

e.g., granite fractures

Groundwater

Deep (hundreds of feet) accumulations of groundwaters may have taken thousands of years to accumulate; significant volumes of groundwater are not typically found below about 2300 feet (see slide) Why?

Groundwater Flow Rates

Groundwater flow rates depend on two factors: 1) the permeability of the rock or sediment, and 2) the slope of the water table (tilt of the rock or sediment body to the ground surface)

Groundwater flow rates vary widely from a few inches a year in impermeable materials to perhaps 500 – 10000 ft/day in very porous and permeable materials (e.g., some gravels) (see figure)

(water-tableslope)

Groundwater

On the average, groundwaters flow a few inches to about a foot per day; remember this is a gross average

Artesian Springs

An artesian system requires a confined aquifer (an aquifer directly overlain and underlain by low-permeability rocks) to form and is defined as a system where the water rises under its own pressure (no pumping required) past the top of the aquifer (see slide)

Geologic Work of Groundwater

Certain rocks (e.g., limestone) are prone to slow dissolution by slightly acidic groundwaters – what is the primary acid?

The dissolving of these rocks may lead to the formation of caverns/caves, sinkholes and other unique features often called “karst topography”(see slides)

Acidic soil water

Limestone or similarly solublebedrock

Caverns exposed when water table lowers

Cavern deposits of precipitated rock (usually limestone)

Geologic Work of Groundwater

Sinkholes – depressions formed by the collapse of the ground surface into an underlying void (cavern)

Sinkholes vary in size and are fairly common in areas underlain by cavernous limestone

Think about the potential hazards (obvious and nonapparent) of sinkholes as we view the following slides

Geologic Work of Groundwater

Karst topography – landscape, predominantly formed by the dissolution of soluble bedrock like limestone, that typically hosts sinkholes, sinking (disappearing) streams, and caverns/caves (see slide)

Approximately 25% of the world’s population lives atop karst topography!

Consequences of Groundwater Withdrawal

If groundwater is removed faster than it is replenished the water table lowers, but not uniformly as one may think

Cone of depression – a cone-shaped drawdown in the water table immediately adjacent to a pumping well (see slide)

Possible consequences: negative impact on the water levels in nearby wells and ground subsidence (see slides)

Effect of land subsidence

Geotimes, July 2008

Consequences of Groundwater Withdrawal

Remember: in many major metropolitan and intensively farmed areas groundwater is essentially a nonrenewable resource and groundwater depletion is problematic (see slide)

What is meant by the term nonrenewable resource?

Shaded sections represent sections of the U.S.where groundwater extractionrates significantly exceedrecharge rates

Groundwater Depletion West of The Mississippi

Consequences of Groundwater Withdrawal

Along marine coastlines or on oceanic islands, excessive withdrawal of groundwaters can facilitate a form of groundwater pollution called “saltwater intrusion” (see figure)

Other Consequences of Urbanization

Urbanization can result in a loss of groundwater recharge area if significant portions of ground overlying the aquifer are covered by impermeable materials (e.g., asphalt) or buildings (see figure); draining and infilling wetlands also reduces recharge

Other Consequences of Urbanization

Artificial recharge can help reduce this problem (see figure)

Potential problems?

Water Supply and Use Topics

Water Supply and Use

Although a seemingly tremendous volume of precipitation falls on average upon the surface of the contiguous U.S. daily (see slide), the precipitation and subsequent outcomes are not uniform (see slide)

Therefore water supplies in the contiguous U.S. vary in volume and quality

Numbers representbillions of gallonsper day

Water Supply and Use

Note the difference between “water withdrawals” (water withdrawn from a source) and “conveyance loss” and “consumption” (consumptive use – water not returned to the source) (see slides)

Water Supply and Use

The increased demand for water accompanying population growth and expanded development has led to bitter legal battles and disputes, within and between nations, over water access rights (see slides)

Water Supply and Use

Egypt pushes Ethiopia to scrap Nile dam Published: Oct. 19, 2012 at 10:50 AMCAIRO, Oct. 19 (UPI) -- Egypt increasingly views Ethiopia's plan to build a massive 6,000-megawatt hydroelectric dam on the Nile River as a threat to its national security because it will seriously cut the Arab state's water supplies.

Egypt depends on the Nile for virtually all of its water and is mounting a major diplomatic and economic campaign to scupper the plan. "Even direct military action by Egypt cannot be ruled out," observed the U.S. global security consultancy Stratfor.

Both countries have undergone major political upheavals recently, which have added to the tension in a long-running battle for control of the world's longest river which rises in the Ethiopian highlands.

Egypt's Muslim Brotherhood now controls the presidency and Parliament following the February 2001 downfall of longtime dictator Hosni Mubarak and is locked in a struggle for supremacy with the military.

Longtime Ethiopian ruler, Prime Minister Meles Zenawi, as harsh a dictator as Mubarak and whose ethnic Tigray group has long dominated the military, died Aug. 20, leaving a leadership vacuum and internal rivalries.

What’s the GreatLakes Compact?

Great Lakes Compact

As stated in the adjacent article the U.S. Congress and president must still approve this legislation

Source: Oakland Press, 7/10/08

This legislation was subsequently approved by the Congress and president

Water Supply and Use

Adequate supplies of clean water will be one of the most significant challenges worldwide in the 21st century

See figure; 1700 cubic meters per person per year of fresh water is considered adequate

Water Supply and Use

Depending on the situation, one or more measures may be undertaken to extend water supplies; the three primary water supply extension measures include:

Conservation Interbasin Water Transfer Desalination

Water Supply Extension Measures

Conservation – as population increases, significant reduction in water withdrawals won’t occur due to conscious deprivation but by advances in technology which produce the same outcome with less water

Examples?

Examples of?

Water Supply Extension Measures

Interbasin Water Transfer – movement of water from one drainage basin to another (e.g., via aqueducts or pipelines)

Is this a relatively new idea? Potential implications for the Great Lakes

region? (Don’t forget about the Great Lakes Compact)

Water Supply Extension Measures

Desalination – conversion of saline to fresh water via filtration or distillation (see figure)

Potential disadvantages?

Water Supply Extension Measures

If proven valid, could the sub-seafloor waters be desalinated and shipped via pipeline or some other method?

Final Thought

Relatively new idea: what’s your (our) “virtual” water use? (The total amount of water used to create a product.)

Example: most studies suggest a pound of beef requires, minimally, nearly 15- 20 times more water to produce than a pound of grain

See following table and figure

Virtual Water Use

Gallons used to produce one pound

Gallons used to produce one item

Beef - 1857 Blue Jeans Pair - 2900

Pork - 756 One Cotton Bedsheet - 2800

Processed Cheese - 589 One Hamburger - 634

Chicken - 469 One Cup of Coffee - 37

Yogurt - 138 One Cup of Beer - 20

Corn - 109 One Cup of Tea - 9

Source: National Geographic, April 2010

Water Quality Measures

Concentrations of water contents are routinely measured in parts per million (ppm) and parts per billion (ppb)

1ppm = 1 milligram (mg) of a dissolved substance per liter (L) of solution; 1 ppm = 1 mg/L

1 ppm = 1000 ppb; 1 ppb = 0.001 mg/L Some substances can now be measured in

concentrations as low as 1 part per trillion!

General Water Quality Measures

Total Dissolved Solids (TDS) – the total amount of dissolved solids in solution; most public water supplies can’t legally distribute water with a TDS value > 500 ppm

Be careful: a TDS value < 500 ppm doesn’t ensure potable/healthy water

General Water Quality Measures

Water hardness – a measure of the total amount of calcium and magnesium dissolved in a water source

Hard water – water whose dissolved calcium and magnesium levels exceed 100 ppm

Why do people usually soften hard household waters and what are the health risks of softened water to specific populations?

Assessments of Analytical Measures

Chemical analysis can be qualitative or quantitative in nature

Qualitative analysis – chemical analysis that determines the presence of a substance above a certain detection threshold (e.g., dissolved arsenic in drinking water above 2 ppb)

Quantitative analysis – chemical analysis that seeks to accurately measure the amount of a substance

Assessments of Analytical Measures

Analytical precision – a measure of the reproducibility of results – Do you obtain the same, or nearly the same, results on repeat analyses of samples of the tested material?

Analytical accuracy – a measure of how close the measured value is to the true value

Do not use the terms “analytical precision” and “analytical accuracy” interchangeably!

Water Testing Laboratory

Conduct all analyses first; review data and answer questions at home if necessary – lab data sheets are due at the beginning of next class

Tips: pH and phosphate are two different tests! For the pH test, follow instructions (C) for testing waters of unknown pH

Phosphate test: follow instructions for low range Hardness test : follow directions for total hardness Dissolved oxygen: follow directions on inside cap cover

of test kit; begin with sample collection and preservation