• GEOLOGY 106
• October 21, 1996

RIVERS

• SLIDES OF COLORADO RIVER FLOOD

• Underground rivers
• Dr. Science and ground water
• Water Table
• Water Witching

OUTLINE OF GROUNDWATER LECTURE

• Importance
• Concepts
• Examples
• Contamination
• Remediation

IMPORTANCE OF GROUNDWATER

• Major source of water (agricultural, domestic, and commercial)
• Large reservoir of water on land
• Involved in accumulation of petroleum and natural gas.
• Form heated fluids that form metal deposits
• Privide ìlubricantî for earth movements and metamorphic processes.

PROBLEMS

• Slow moving fluid in the earth
• Contaminants difficult if not impossible to cleanse from system
• Exploited at rate greater than renewed (e.g. mined).
• Overdrawing causes subsidence of ground
• Easy to contaminate along coasts (seawater intrusions)

GROUNDWATER CONCEPTS TO KNOW

• Porosity
• Permeability
• Capillarity
• Available vs Unavailable water
• Aquifer vs Aquitard
• Saturated/Unsaturated Zones
• The Water Table
• Darcy's Law
• Flow systems

POROSITY

• Pore space in rock
• Granite < 1%
• Sand 25-40%
• Shale 50-90%
• Pumice > 50%
• (floats on water)

PERMEABILITY

• Connected pore space

CAPILLARITY

• Demonstration

Available vs Unavailable water

• Capillary water unavailable
• Finer grained sediment has higher porosity, but lower permeability
• Fine grained sediment has higher % of water as capillary water

Aquifer vs Aquitard

• Aquifer - capable of movement of water sufficient to serve wells, springs (conductive rock)
• Aquitard - Resists movement of water through pores (resistive)

Saturated/Unsaturated Zones

Unsaturated zone - pore spaces generally occupied by air and moisture and water on its way down to the saturated zone (Vadose water)

• Saturated zone - all pore spaces filled with water.

The Water Table

• Upper boundary of the saturated zone defines the Water Table
• Generally marked by a capillary fringe
• A outcrop of the water table (intesection of the land surface with water table) defines a spring

Seeps, flowing

springs,

lake edges, ...

Darcy's Law

Flow systems

• (unconfined, perched, confined, artesian)

Water Pathways

GROUNDWATER PROBLEMS

• Overuse
• Contamination
• Subsidence
• Saltwater Intrusion

REMEDIATION

RETURN TO SYLLABUS