homework geology #5

1.aquitard 2.confined aquifer 3.unconfined aquifer

1. impermeable layer that prevents flow. 2.rock or regolith that can store and transmit water but is contained between two impermeable layers. 3.rock or regolith that can store and transmit water and receives its recharge directly from the atmosphere.

1. dissolved load 2. bed load 3. suspended load

1. ions in solution that are dispersed throughout the flow. 2. larger sediments that bounce, roll, or slide along the bottom. 3. fine sediments that are held up by the water and carried throughout the water column.

What percentage of the Earth's total freshwater is in the form of groundwater?

30.1%

A typical rate of groundwater flow for many aquifers is approximately ________.

4cm/day

What percentage of Earth's water is in the form of seawater?

97.2%

A B C D

A- unsaturated zone B- capillary fringe C- water table D- zone of saturation

Which of the following is not a factor that will influence infiltration of groundwater?

Acidity of precipitation

What is the difference between an aquifer and an aquitard?

An aquifer is a rather permeable rock, whereas an aquitard is an impermeable rock.

Briefly describe a general drainage basin.

An area drained by a stream is called a drainage basin, which is bounded by an imaginary line called a divide. The divide can be clearly visible as a sharp ridge, or it could be difficult to determine in subdued topography.

How does an oxbow lake form?

An oxbow lake forms when the bend of a meandering river is isolated from the river because erosional forces create a cutoff in the main river channel. This isolated bend becomes the oxbow lake.

Why might the ground subside after groundwater is pumped to the surface?

As water is withdrawn, the water pressure drops, and the sediment is left to support the weight on top of it. As a result, the sediment packs more closely together, causing the ground to subside.

Which of the choices below correctly defines base level and differentiates between ultimate base level and local (temporary) base level?

Base level is generally defined as the lowest elevation to which a stream can erode its channel. The ultimate base level is sea level; local base levels are lakes, resistant layers of rock, and rivers that act as base levels for their tributaries.

What is the difference between capacity and competence?

Capacity is the maximum load of solid particles a stream can transport per unit of time, whereas competence is a measure of a stream's ability to transport particles based on size rather than quantity.

What is groundwater, and how does it relate to the water table?

Groundwater is water that occupies the zone of saturation within the ground. The water table is the upper limit of the groundwater.

In order for an aquifer to be useful for reliable water extraction, what kind of porosity and permeability should it have?

High porosity, high permeability

The ________ describes the path water takes as it moves between the land, the ocean, and the atmosphere.

Hydrologic Cycle

What significant problem might arise when groundwater is heavily pumped at a coastal site?

If the groundwater withdrawal exceeds recharge, the saltwater will become high enough to be drawn into the wells.

Streams generally receive their water from two sources. What are those two sources?

Overland flow and groundwater

Which of the following is not one of the three zones of a river system?

Sediment Capacity Zone

What is the wetted perimeter of a stream?

The amount of flow in contact with the banks and bed of the channel

What will happen to the water level in the stream if the water table is below the level of the stream channel?

The stream will lose water to the groundwater system.

How will channel velocity change along the longitudinal profile of a stream?

Velocity will start low and gradually increase toward the mouth due to increasing discharge downstream

What is a stream's longitudinal profile?

a cross-sectional view of a stream from the headwaters to its mouth

What is permeability?

ability to transmit water

in what ways does a stream transport its load, and which part of the load moves most slowly?

as a suspended load, as a dissolved load, and as a bed load, which is the slowest mode of particle transport in streams

Which part of a stream's sediment load moves the slowest?

bed load

A ________ stream consists of a complex network of converging and diverging channels that weave around channel bars.

braided stream

________ is the maximum load of solid particles a stream can transport per unit time.

capacity

________ is a measure of a stream's ability to transport particles based on size rather than quantity.

competence

What feature develops if a well is withdrawing more groundwater than an aquifer can naturally replace, resulting in a dimple in the water table?

cone of depression

The ________ is an elevational point that divides an entire continent into large drainage basins.

continental divide

the volume of water flowing past a certain point in a given amount of time is a rivers _______

discharge

what is base level?

downward limit of erosion

the geographical area where all surface water converges to one location is called its

drainage basin

________ is a term used to describe how the water table around a well becomes lower as water is taken from the subsurface.

drawdown

a river with a well-developed ________ has a flat low-lying channel and experiences flooding during periods of high discharge

floodplain

________ are flat areas along streams that are created by the deposition of alluvium and is subject to periodic inundation.

floodplains

During what periods would streams see the greatest erosion and transportation of sediment?

floods

Which of the following would increase flow velocity?

having a narrow, deep channel

What factors would decrease flow velocity?

having a rough channel, a decrease in stream discharge, a decrease in gradient of the stream

In which part of a stream's course would one typically find bedrock channels?

headwaters

the _____ headwaters of a river have a steep gradient, high channel roughness and low water volume

headwaters

To be a gaining stream, the elevation of the water table must be ________ than that of the surface of the stream.

higher

Which of the following uses the largest percentage of the Earth's groundwater?

irrigation

a stream with a low to moderate gradient, carrying most of its load in suspension should be characterized by many curves and bends called

meanders

a delta forms at the ________ of a river, where the velocity of the water flow decreases and deposition is highest

mouth

Where is the zone of sediment production in a stream?

near the headwaters

In terms of competence, if the velocity of the stream triples, the impact force of the water will increase ________ times.

nine

________ is when groundwater is being replenished. ________ is when groundwater is flowing back toward the surface.

recharge, discharge

According to the hydrologic cycle, once precipitation has fallen on land, what paths might the water directly take?

runoff into the sea, runoff into a river, infiltration into the ground, evaporation/transpiration

What is the ultimate base level?

sea level

What groundwater feature forms where the water table intersects with the Earth's surface, creating a natural outflow of groundwater?

spring

When rain falls on land, what factors influence the amount of water that soaks in?

steepness of slope, amount of vegetation on the surface, intensity of rainfall, and nature of the surface material

Transpiration moves water from _______

the biosphere to the atmosphere

In general, how do the channel width, channel depth, flow velocity, and discharge change between the headwaters and the mouth of the stream?

the channel width, channel depth, flow velocity, and discharge all increase as the stream approaches the mouth.

Undulations of the water table mimic those of the ground surface. What would happen to those undulations in the water table if all rain were to cease?

the water table would become flat??

Which of the choices below is not a factor that causes infiltration and runoff to vary from place to place and from time to time?

time of the day

match location to the stream from top to bottom

top- headwaters middle-meandering channel bottom-delta

What is porosity?

volume of pore space in a material

How will the water table respond when there is a drought?

water table will fall

How will the water table respond if it is a wet spring?

water table will rise

The ________ is the point in the subsurface where 100% of the pore spaces are filled with water.

zone of saturation

What are the three main zones of a river system from highest to lowest?

zone of sediment production, zone of transportation, and zone of deposition