Geology chapter 12

saturated zone

part of subsurface where the pores are completely filled with water

springs

places where water flows naturally from the ground because the water table is above the ground surface

Permeability

property that expresses how easily a gas or liquid can pass through rock or sediment (more permeable means material will allow water to pass through it at higher rate)

velocity head

related to energy of moving water

aquitard

rock layer that inhibits flow of water so that it flows very slowly

aquifer

saturated, permeable rock unit from which water can be produced in economic quantities

confined aquifers

separated from atmosphere by a layer of material that has a significantly smaller permeability, the confining layer

Which of the following features are indicative of a landscape defined by karst topography?

sinkholes solution valleys

What is the water table?

the top of the saturated zone beneath Earth's surface

solution valleys

valley-like depression formed by a linear series of sinkholes or collapse of the roof of a linear cave

Porosity

% of the volume that is not made up of solid material like mineral grains and cement

How does the use of water by humans affect the water table?

Use of water by humans increases discharge, resulting in lowered water tables

disappearing stream

streams that drop below the ground surface, flowing into open joints or caverns

sinkholes

surface depressions formed through several different processes including collapse of caves or other underground void spaces

ground water

water that exists in fractures and in tiny spaces b/w grains below earth's surface

If the elevation of the water surface of a lake is 715 feet above sea level, what is the elevation of the water table at the lake?

715 feet above sea level

Unsaturated Zone

Area above the water table where the pore spaces are not filled completely with water

Zone of Saturation

Area where the pore spaces are completely filled with water

cone of depression

Conically shaped depression in the water table formed near a well. Is negligible in domestic wells.

Why does groundwater discharge to Earth's surface?

Earth's surface is irregular, and permeability decreases with depth within Earth

Pore Spaces

Gaps between pieces of sediment and fractures/cracks in rocks. Allows solid rock and soil to hold water.

Shape of the Water Table

Is not flat, but rather reflects the topography of the surface

Which of the following statements about the water table is true?

The water table is high under hills and low under valleys. Lakes and streams are surface expressions of the water table. The water table can be lowered if too much groundwater is pumped out.

How would the water table be affected if Earth were made up of uniform, permeable material?

The water table would not exist

Which of the following would produce a LOWER water table?

a decrease in the amount of recharge to groundwater an increase in the amount of discharge to surface water

flow line

a path that light non-aqueous phase liquids flow along the water table perpendicular to the water-table contours

Water Table

boundary b/w unsaturated and saturated zones

Karst topography can be identified even when looking at a topographic map. Which of the following features would show up easily on a topographic map, indicating a karst landscape?

closed depressions

(A) __________ will form when high-capacity wells pump too much water from the subsurface, resulting in a dimple in the water table.

cone of depression

hydraulic gradient

describes hillside's steepness over some horizontal distance of the water table

pressure head

distance from the bottom of piezometer on the top of the water in the pipe

elevation head

elevation of the bottom of a monitoring well or piezometer (a plastic or steel pipe w/ a screen bottom end to keep sediment from rising into the well)

unconfined aquifers

have water table that is in contact with the atmosphere either directly or through interconnected pores or fractures in an unsaturated zone