WaterTerms

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The terms porosity and permeability are related.

Porosity is a measure of the amount and size of pore space within an earth material, such as soil, clay, gravel, silt, rock, etc.

Some rocks and soils are very porous, while others have very little space between the particles.

Porosity is how much water a material can hold. It is usually stated as a percentage of the material’s total volume.

Porosity vs. Permeability

Permeability is a measure of the ability of an earth material to let water pass through it.

Permeability is affected by the size of the particles and shape of the spaces between the particles.

Some materials have many spaces between particles, while others have virtually no space between particles and are called impermeable.

Porosity vs. Permeability

Water flows between the spaces in the material.

If the spaces are close together, such as in clay based soils, the water will tend to cling to the material and not pass through it easily or quickly.

If the spaces are large, such as in the gravel, the water passes through quickly.

Porosity vs. Permeability

There are two other terms that are used with water: percolation and infiltration.

Infiltration is when the water enters the soil surface after falling from the atmosphere.

Percolation is the downward movement of water from the surface of the land into the soil or porous rock, mainly caused by gravity.

Percolation and Infiltration

Particle Sizes And Pore Space:

Groundwater is water that flows through the pores in the rocks and soil beneath the surface of the ground.

The groundwater trickles downward until it reaches an impermeable layer of soil or rock. 

We use wells and springs to pull groundwater back to the surface to drink.

Ninety-eight percent of Earth’s available freshwater is groundwater.

Groundwater vs. Surface Water

Surface water includes rivers, streams, lakes, ponds, oceans, and even the water that runs down streets during thunderstorms.

Surface water will, unless interfered with, flow downhill until it reaches a creek or stream. The creek or stream will eventually feed a river that will flow into the ocean. Along the way, some water will evaporate back into the atmosphere and will fall back to the Earth as rain. 

Surface water supplies 80% of the water used on a daily basis.

Groundwater vs. Surface Water

Groundwater vs. Surface Water

Surface water which has not yet flowed into a creek is called runoff. Bare ground allows a great deal of runoff to occur. Plants and dug ponds (a small, shallow pond created artificially by digging a depression in the land) reduce the amount of runoff.

Watershed Diagram

A watershed is an area of land where all of the surface water within a specified area drains downward and flows to the same place.

Each drainage basin, or watershed, is separated topographically from adjacent basins.

Watershed vs. Aquifer

An aquifer is a natural, underground area where large quantities of ground water fill the spaces between rocks and sediment and accumulates.

This water is available for use by using wells to pump out the water.

Aquifer

Texas Aquifers

The state of Texas has 23 aquifers that cover approximately ¾ of the state.

The Ogallala Aquifer accounts for about 90% of the water in all of Texas aquifers.

Groundwater from Texas aquifers is used for irrigation, city use, manufacturing, and livestock production.

Pumping water from many aquifers in Texas has resulted in a significant lowering of the water table. A map showing watersheds in

Texas

Less permeable rock below an aquifer that keeps groundwater from draining away is called a confining layer or aquitard.

The water table in an aquifer is at the very top of the zone of saturation.

The zone of saturation is where water completely fills all the interconnected pore spaces.

More about Aquifers

Water Table The water table is the

upper surface of ground water below which the soil or rocks are permanently saturated with water and where the pressure of water in the soil equals the pressure of the atmosphere.

The water table fluctuates both with the seasons and from year to year because it is affected by climatic variations and the amount of precipitation used by vegetation. It also is affected by withdrawing excessive amounts of water from wells.

Pollution is the introduction of a contaminant into the environment.

It is created mostly by human actions, but can also be a result of natural disasters, such as flooding.

Pollution has a harmful effect on any living organism in an environment, often making it impossible to sustain life.

Pollution to drinking water can cause diseases.

Pollution