Unit 4 Key Terms and Ideas

Pools or Reservoirs

The places where you can find water

Fluxes

Flows from one reservoir to another, in units of mass per time or volume per time

Consumptive Water Uses

Water is removed from water source and used

Non-consumptive Water Uses

Water is not taken from the reservoir, or is returned to the reservoir soon after being used

Overexploitation

Extracting too much water

Subsidence

The vertical sinking of the Earth’s surface in a region

Salinization

The accumulation of salt in water, making it largely useless

Groundwater

Water that resides under the surface of the Earth, mostly in pores or cracks of rock or sediment

Vadose (Unsaturated) Zone

The region of the subsurface above the water table, the pore space is mostly air

Phreatic (Saturated) Zone

The region below the water table where pore space is filled with water.

Water table

The boundary between the Vadose and Phreatic Zones

Aquifers

Rocks or sediments in the saturated zone, from which water can be reasonably removed using a well

Unconfined Aquifers

Aquifers whose upper boundary is the water table

Confined Aquifers

An aquifer isolated from the surface by an aquitard

Perched Aquifer

A local aquitard causes water to "perch" atop it, above the regional water table

Aquitard

Sediment or rock that does not transmit water easily and therefore retards the motion of the water.

Porosity

The fraction of the rock's volume that consists of pore space

Permeability

The ease with which water can move through pore space in a rock or other material

Potentiometric Surface

The level groundwater naturally rises to in a well because of its pressure.

Recharge

When new water from the surface infiltrates downward and adds to the groundwater in an aquifer

Discharge

Discharge is when groundwater leaves an aquifer and flows back to the surface into streams, springs, wetlands, or wells.

Gaining Streams

A stream that receives water from the groundwater

Losing Streams

A stream that loses water to the groundwater