S. 17 Groundwater Final Test Review

A series of flashcards covering key concepts and details related to groundwater extracted from lecture notes.

What percentage of Earth's water is drinkable?

Less than 1%

What is the approximate percentage of groundwater volume compared to ocean water volume?

~1%

What purpose does two-thirds of groundwater use in the U.S. serve?

Irrigation

What is the average U.S. per capita water use closest to?

100 gallons/day

Which U.S. regions receive the most precipitation?

Southeast and Pacific Northwest

What does a water surplus (precipitation minus evaporation) mean?

Water is available for infiltration

What does porosity refer to?

Percentage of open space in a rock

Which materials typically have the highest porosity?

Sands and gravels

What does permeability describe?

How well pores are connected to allow fluid flow

What is a rock layer that permits water flow at commercial rates called?

Aquifer

What is a low-permeability layer that restricts water flow called?

Aquitard

How is the water table typically characterized?

A subdued replica of local topography

Where is groundwater replenished?

Recharge areas

Why can water rise above land surface in a confined aquifer?

Pressure builds between aquicludes

When does an artesian well occur?

Water flows above land surface due to pressure

How does a perched aquifer form?

Water accumulates above a local aquitard

What are typical flow rates in the subsurface?

Centimeters per day or slower

What can overextraction of groundwater cause?

Cones of depression

What can regional overextraction relative to recharge lead to?

Ground subsidence

How does conductivity (K) differ from permeability (k)?

Conductivity depends on both rock and fluid properties

What is most water on Earth?

Salt water

What does the water table represent?

The top of saturated pore space

How is an aquiclude best described?

A barrier to water flow

Why does pollution persist in groundwater?

Slow (cm/day or less) flow rates

What characterizes a confined aquifer?

Aquicludes above and below