CHAPTER 20:GROUNDWATER

Groundwater

• It is estimated that there is 3000 times more water stored as groundwater in the upper 800 meters of continental crust than the water found in all the world’s rivers and streams. (United States Geological Survey )

Groundwater

• Groundwater is our most important source of fresh water.

• About 30% of the population of Canada depends on groundwater.

Groundwater is present where the material of the crust has pores or fractures

There Are Several Types of Earthquake Hazards

What’s the term used to describe the boundary zone between the unsaturated and saturated zones?

The Water Table rises and falls with the seasons

Most water wells are drilled with truck-mounted drill rigs

Groundwater is fed by snowmelt and rainfallin recharge areas

Streams

• In some situations groundwater contributes to the base flow of a stream. In others, streams contribute to the groundwater.

What is the difference between a connected losing stream and a disconnected one?

Wetlands

• Wetlands are critically important for storage of both surface and groundwater

Hydraulic Pressure

• Groundwater moves in response to gravity and hydraulic pressure

Aquifer

• An aquifer is body of rock or unconsolidated sediment through which groundwater can flow

Why should deep groundwater take many times longer to reach the discharge area than shallow groundwater?

Permeability and porosity

Of the following pairs of situations, which should have the greater permeability and why: (a) versus (b), (a) versus (c), (a) versus (d), (e) versus (f)?

Hydraulic Gradient

• In this situation the hydraulic gradient is the slope of the water table.

Darcy’s Law

Porous Materials and Fractured Rocks Hold Groundwater

Porous Materials

Fractured Rocks

Aquifer Terminology

What is the difference between the water table and the potentiometric surface?

Groundwater is vulnerable to many different sources of pollution

Groundwater Animation

Hard Water

• Groundwater contains a wide range of dissolved ions, most at levels that are higher than in surface water.

• Water with high levels of calcium or magnesium is known as hard water and often leaves coatings of white mineral precipitates on plumbing fixtures.

Apart from Ca and Mg, what are some common dissolved ions in groundwater?

Saltwater Intrusion

What can people living near to the coast do to reduce the likelihood of saltwater intrusion?

An improperly functioning septic field can be a source of groundwater contamination.

Contaminant plumes

• Common human activities contaminate groundwater

Salt Contamination

• It is common to combat icy conditions by spreading salt on roads and highways.

• This results in salty runoff that percolates into the unsaturated zone.

Landfills, pesticides and undergroundfuel storage tanks

It is estimated that there are >10 million underground storage tanks buried in the United States and that 70%

of them leak.

Monitoring wells

How many abandoned gas stations—surrounded by chain-link fencing—can you find in your region?

Are there examples of some of these types of contamination in your region?

Groundwater contamination in Canada’s far north

Who is responsible for cleaning up contamination at DEW-line sites like Cape Dyer?

Groundwater remediation includes several types of treatments

• Air sparging• Extraction wells• Recirculation wells• Aquifer fracturing• Injection wells

Groundwater remediation includes several types of treatments

• Permeable reactive barriers• Bioremediation• Phytoremediation• Thermal or electrical treatments

Hydrological Regions of Canada

From: Natural Resources Canada. 2007. Groundwater Mapping Program. Hydrogeological Regions.

Springs exist where groundwater naturally comes to surface.

Spring water has deposited tufa (calcium carbonate) over this outcrop at Johnston Canyon in the Alberta Rockies

Karst topography is also a product of groundwater

What type of rock is found in karst regions, and what

property of that rock facilitates the development of karst?

As is hydrothermal activity.

Geyser Fumarole Hot Spring

Speleothems

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