Porosity and Permeability in Earth Materials

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Questions and Answers

What does porosity measure in earth materials?

The density of solid particles

The size of water droplets

The flow rate of water through soil

The amount and size of pore space (correct)

What is the primary characteristic of impermeable materials?

They can hold large amounts of water

They have virtually no space between particles (correct)

They have many spaces between particles

They allow water to pass easily

Which term refers to the downward movement of water caused mainly by gravity?

Percolation (correct)

Infiltration

Transpiration

Evaporation

What is groundwater primarily composed of?

Water that flows through the pores in rocks and soil Signup and view all the answers

Which statement is correct regarding surface water?

It flows downhill unless obstructed Signup and view all the answers

In what scenario does infiltration occur?

When water enters the soil from the atmosphere Signup and view all the answers

What percentage of Earth's available freshwater is represented by groundwater?

98% Signup and view all the answers

What happens to water that runs off bare ground?

It allows a considerable amount of runoff to occur Signup and view all the answers

What is the primary function of a watershed?

To drain surface water to a single location Signup and view all the answers

Which statement accurately describes an aquifer?

It is a natural underground area filled with water. Signup and view all the answers

What is the role of the Ogallala Aquifer in Texas?

It is the main source of irrigation water in Texas. Signup and view all the answers

Which layer below an aquifer prevents groundwater from draining away?

Aquitard Signup and view all the answers

What causes fluctuations in the water table?

Seasonal changes and precipitation levels Signup and view all the answers

How can pollution affect drinking water sources?

It can pose health risks and cause diseases. Signup and view all the answers

What typically leads to the lowering of the water table in aquifers?

Withdrawal of excessive amounts of water from wells Signup and view all the answers

What is the water table?

The boundary between saturated and unsaturated soil Signup and view all the answers

Study Notes

Porosity vs. Permeability

Porosity is the amount and size of pore space in earth materials (soil, clay, gravel, rock).
Some materials are very porous (large spaces), while others have little space between particles.
Porosity is the amount of water a material can hold, usually expressed as a percentage of the material's total volume.
Permeability is the ability of an earth material to let water pass through it.
Permeability depends on the size and shape of spaces between particles.
Some materials have many spaces between particles, and are permeable. Others are impermeable (virtually no spaces).
Water flows between spaces in the material.
If spaces are small (clay), water clings and doesn't pass easily.
If spaces are large (gravel), water passes quickly.

Percolation and Infiltration

Percolation and infiltration are terms relating to water movement.
Infiltration is when water enters the soil surface.
Percolation is when water moves downwards through the soil or porous rock, mainly by gravity.

Groundwater vs. Surface Water

Groundwater flows through pores in rocks and soil beneath the surface.
It trickles downward until it reaches an impermeable layer.
Wells and springs obtain groundwater.
98% of Earth's available freshwater is groundwater.
Surface water includes rivers, streams, lakes, ponds, oceans, and water running during storms.
Surface water flows downhill until reaching a creek or stream, eventually flowing into oceans.
Some surface water evaporates and returns to Earth as rain.
Surface water supplies 80% of daily water use.
Runoff is surface water that doesn't flow into creeks or streams immediately (bare ground has lots of runoff).
Plants and dug ponds reduce runoff.

Watersheds and Aquifers

A watershed is an area of land where all surface water drains to the same place.
Watersheds are topographically separated.
An aquifer is a natural underground area with large quantities of groundwater.
Groundwater fills the spaces between rocks and sediment.
Texas has 23 aquifers.
The Ogallala Aquifer provides 90% of Texas' aquifer water.
Groundwater in Texas aquifers is used for irrigation, city use, manufacturing, and livestock.
Pumping water from aquifers has lowered the water table significantly.

Water Table

The water table is the upper surface of groundwater.
Soil or rocks are permanently saturated below the water table.
Water pressure at the water table equals atmospheric pressure.
The water table fluctuates seasonally and annually due to precipitation and vegetation use.
Excessive water withdrawal from wells affects the water table.

Pollution

Pollution is the introduction of contaminants into the environment.
Pollution is mostly caused by human actions, but can also result from natural disasters (e.g., flooding).
Pollution harms all living organisms; it can make life unsustainable.
Pollution of drinking water causes diseases.

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Description

Explore the concepts of porosity and permeability as they relate to various earth materials. This quiz covers the definitions, differences, and importance of these properties in water movement through soil and rocks. Test your understanding of infiltration and percolation processes!