PM 9 Running and Groundwater

A stream begins at an elevation of 200 meters and flows a distance of 400 kilometers to the ocean. What is the average gradient?

0.5 m/km

Approximately how much of Earth's water supply is saline?

98%

At which of the following locations is erosion occurring?

A C E

Which of the circumstances listed below can lead to the formation of a spring?

An aquitard blocks the downward movement of groundwater, causing it to move laterally. Where the permeable rock layer crops out at the surface, the water gushes forth in a spring.

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 in subdued topography, may be difficult to determine.

________ is an abandoned, cutoff, meander loop.

An oxbow

How does an oxbow lake form?

An oxbow lake forms when the bend of a meandering river is isolated from the river when it is cut off from the main river channel. This isolated bend becomes the oxbow lake.

Which of the following is a requirement for an artesian system to exist?

Aquitards must be present both above and below the aquifer.

During a summer with little rainfall, your house on a hill slope experiences an interval during which your well runs dry. You have to borrow water from your neighbor who lives downslope from you. Why does your neighbor have water when you don't?

As the water table drops due to the lack of precipitation, it goes below the base of your well.

At which of the following locations is deposition occurring?

B D

How does groundwater create caverns?

Caverns are created when acidic groundwater dissolves and carries away limestone.

Which portion of the stream is the most likely to become an oxbow lake in the near future?

D

Which of the following statements about drainage basins is FALSE?

Drainage basins only contain one river.

Look at the figure below and determine which of these is true in terms of relative pressure and water table depth at locations A and B.

Location A has a higher pressure

How are oxbow lakes formed?

Oxbow lakes form when one meander erodes into another, cutting off water to part of the stream channel.

________ is the volume of voids or open space in a rock or unconsolidated material.

Porosity

Contrast porosity and permeability.

Porosity is the percentage of the total volume of rock or sediment that consists of pore spaces, whereas permeability is the ability of a rock or sediment to transmit fluid.

The Mammoth Plateau near Mammoth Cave National Park is higher in elevation than the surrounding landscape and separates the Sinkhole Plain from the Green River. As the Mammoth Plateau is a major topographical barrier, how does precipitation that falls on the Sinkhole Plain make it into the Green River Valley?

Precipitation infiltrates into the subsurface via sinkholes and flows through subterranean passages to the Green River Valley.

________ make up the suspended loads of most rivers and streams.

Silt and clay-sized, detrital grains

How do stalactites form?

Stalactites form on the roof of a cave from the deposition of calcium carbonate by dripping water.

What does the hydrologic cycle describe?

The hydrologic cycle describes how liquid and gaseous water move between the ocean, atmosphere, and land.

What would happen to the oceans if surface runoff and groundwater flow did NOT occur?

The oceans would become smaller.

What is evapotranspiration?

The transfer of water directly from the land's surface into the atmosphere

How does the water table change around a pumping water well?

The water table elevation decreases.

The city of New Orleans is in the delta of a great river. During hurricane Katrina most of the city flooded but the area along the river, like the French Quarter, did not. Why didn't these areas flood?

These areas were natural levees of the river, and were higher in elevation than adjacent areas.

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

Time of the day

Which one of the following concerning artesian wells is not true?

When the well penetrates the aquifer, the water rises to the bottom of the aquitard above the aquifer.

The amount of meandering that occurs in a stream influences the gradient in which of the following ways?

With more meanders, the stream gradient decreases.

A natural levee is ________.

a depositional feature

What is a meander scar?

a landscape feature formed after an oxbow lake dries up

What is an oxbow lake?

a meander that has been cut off from the original stream channel

What is a natural levee?

a ridge of flood deposits next to a river channel

Which of these is considered to be "storage" part of the hydrologic cycle?

addition to a glacier

Rock, such as shale or clay, or other unlithified sediment can produce layers that are well sorted, but do not allow water to move through them. Which of the following terms is most accurate for this type of layer?

an aquitard

Permeable rock strata or sediment that transmit groundwater freely are called ________.

aquifers

Highly impermeable layers such as compacted clay or shale are known as ________.

aquitards

As shown by the South Dakota example, artesian systems __________.

are able to transmit water great distances from recharge to discharge areas

What term describes a groundwater system in which water in a well rises above the top of the aquifer without use of a pump?

artesian

Where is most of Earth's freshwater found?

as ice at Earth's surface

The hydrologic cycle is ________-right now but because of snow melt, sea level is ________.

balanced; staying the same

What are the three types of loads carried by streams?

bed load, suspended load, dissolved load

Which of the following is not part of the water cycle?

calcium carbonate dissolving in soil water and groundwater

Lowering of the water table around a pumping well results in a cone of ________.

depression

At the head of a delta, the major channel splits into smaller channels that follow different paths to the sea. These smaller channels are known as ________.

distributaries

What is the dominant fluvial process in a clear, sediment-poor stream moving down a steep slope?

downcutting

A ________ refers to an area that contributes to a stream.

drainage basin

Which of the following locations contains the most water in Earth's hydrosphere aside from the oceans?

glaciers

As a hydrogeologist looking for a source of water for a housing development, which of the following attributes would you look for in a layer of sediment or sedimentary rock? CHECK ALL THAT APPLY

high permeability. high porosity.

The source of heat for most hot springs is ________ beneath the surface.

hot igneous material

The capacity of a stream measures the ________ it is capable of transporting.

maximum size of particles

A __________ is located where the pressure surface is above the aquifer, but below the ground.

nonflowing artesian well

At a bend in a river, the main erosion is ________.

on the outside of the bend

Stream discharge is defined as the ________ of water flowing past a specific channel location per unit time.

quantity

The lowest base level for most streams is ________.

sea level

The type and amount of material carried in the suspended load of a stream depends on ________.

settling and flow velocities

Channelization involves making stream channels ________.

straighter

Which of the following rivers is the largest river in North America?

the Mississippi River

Which ocean is Earth's largest?

the Pacific Ocean

What is suspended load?

the fine-grained particles that travel in the water column above the stream bed

What is the cone of depression?

the shape that the water table takes on near a pumping well

The majority of groundwater is stored within which of the following zones?

the zone of saturation

Which of the following zones is the location of the most biological activity?

the zone of soil moisture

The suspended load of a stream ________.

usually consists of fine particles

Which correctly describes four types of drainage patterns?

(1) Rectangular pattern, which develops on highly jointed bedrock; (2) trellis pattern, which develops in areas of alternating weak resistant bedrock; (3) dendritic pattern, which develops on relatively uniform surface materials; and (4) radial pattern, which develops on isolated volcanic cones or domes

Drag the terms in the left-hand column to the appropriate blanks on the right.

1. A(n) incised meander is a bend in a steep narrow bedrock valley. 2. The lowest level to which a stream can erode is called base level. 3. A(n) terrace is the remnant of a former floodplain. 4. Examples of local base level include a stream or a(n) lake. 5. A sweeping bend of a stream which is migrating laterally in a wide, flat valley is called a(n) meander. 6. The flat, broad area surrounding a stream is referred to as a(n) floodplain.

While working on a stream in your field study area, you find that the channel width is 20 meters, the channel depth is 2 meters, and the velocity is 1.2 meters/second. What is the discharge of this stream?How can pieces of rock in contact with a stream bed move?

48 m3/s

Various sources of pollution can contaminate groundwater. Groundwater can carry this pollution to surface-exposed waters such as oceans and rivers, thereby impacting marine and freshwater ecosystems. Groundwater can also transport pollution to wells used for drinking water or for farm irrigation. See the figure below for examples of groundwater pollution sources. The figure below shows an aquifer that has been impacted by liquid leachate from a landfill. Pollution from the landfill affects wells drilled into the aquifer differently. The impact depends on 1) which aquifer (unconfined or confined) that the well is drilling into and whether the aquifer is contaminated, and 2) the location of the well—upslope or downslope of the landfill. The confining layer (also called an aquitard) prevents any contamination from reaching the underlying aquifer, which is the confined aquifer. Compare this to the unprotected aquifer above the confining layer. Also, considering the slope of the land, contamination will likely flow to sources downslope rather than upslope due to gravitational pull. You will determine which well(s) is/are contaminated and which is/are not. Drag the appropriate labels to their respective targets. Each label may be reused.

A - Uncontaminated well C - Contaminated well D - Uncontaminated well

What problem is caused by pumping groundwater for irrigation in the southern High Plains?

A low precipitation rate and a high evaporation rate allow little water to recharge the aquifer.

________ is the boundary line separating adjacent stream drainage basins.

A stream divide

These Google Earth photos show the Colorado River, which has incised downward due to uplift of the Colorado Plateau. The canyon cut by this river is currently flooded due to a dam installed in northern Arizona in 1963, creating Lake Powell. A rincon, or an incised and abandoned meander, can be seen in the following images. The previous and present paths of the river are also outlined. You can see from the north-south line and elevation profile below that the rincon is higher in elevation than the current flooded canyon. This suggests that the river abandoned this meander while it was downcutting. This shortened the river course by six miles. Take a moment to think about how the Colorado River has evolved through time. Focus on how changing base level and stream incision created landforms, such as incised meanders and rincons, and arrange these events accordingly. Rank from oldest to youngest.

A stream migrates laterally across its floodplain developing meanders. This stream terminates at a lake, which is its base level. The base level of the stream is lowered by crustal uplift and the river begins to incise downward. Incised meanders form. A rincon forms by the cutoff of an incised meander, which shortens the river.

In the hydrologic cycle, water that falls on land in the form of precipitation returns to the ocean in which of the following pathways?

All of the responses are correct.

How much of Earth's surface water exists in the oceans?

Almost all of Earth's surface water exists in the oceans.

The Mississippi River has an average discharge of 17,300 cubic meters per second but the ________ River discharges 12 times more water than the Mississippi River.

Amazon

The presence of the Green River has a significant impact on the water table in the area around Mammoth Cave National Park in Kentucky. How does the relationship between the Green River and the water table affect cave passage formation?

As the Green River erodes downward, the water table will lower as the groundwater flows toward the stream, carving new cave passages further from the surface.

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.

Where do deposition and erosion of material occur along a meander?

Deposition occurs on the inside of the meander, whereas erosion occurs on the outside.

Which of the following statements about deposition and erosion around meander loops is true? Choose all that apply.

Deposition occurs where water is moving the slowest along the inside of the loop. Erosion occurs where water is moving the fastest along the outside of the loop.

Below is a list of geographical features. Each one of them is an example of one of the words below. Match one location with the appropriate word it exemplifies. Sort these items into the appropriate bin. Use each item once, and place only one item per bin.

Divide - Appalachian Mountains Watershed - Missouri River Basin Tributary - Big Horn River Trunk Stream - Mississippi River

Match one definition with the appropriate word it defines. Sort these items into the appropriate bin. Use each item once, and place only one item per bin.

Divide - a boundary, usually a hill or mountain, where water will flow in opposite directions on either side Watershed - an area in which all water falling in it flows out through one location Tributary - a river that feeds into another river Trunk Stream - the primary river flowing out of a drainage basin

How does a permeable sandstone compare to a karst limestone in terms of groundwater flow?

Flow is faster in the limestone so pollution is more of a threat.

Water falling in Illinois would ultimately end up where?

Gulf of Mexico

In the late twentieth century, Hidden River Cave had suffered from significant pollution and bad odor. Although various chemical pollutants had been dumped or spilled nearby, none had intentionally been disposed of in Hidden River Cave. How did they end up there?

Hidden River Cave and the dump sites are connected via various sinkholes and subterranean passages.

Read the following descriptions of rocks and layers, and identify the likelihood of each being a good aquifer by grouping them into high and low likelihoods. Drag the appropriate items to their respective bins.

Low Gneiss (metamorphic rock that used to be granite and underwent intense pressure) Granite (igneous rock) with very few to no cracks High Sandstone (sedimentary rock composed of sand grains) Unconsolidated gravel and sand Conglomerate (sedimentary rock composed of various sizes of sediment such as pebbles and sand grains)

The ________ River is North America's largest river in terms of discharge.

Mississippi

How does the formation of a natural levee impact flooding?

Natural levees raise the height of the stream channel, reducing the amount of flooding that will occur on the floodplain.

How does water get from the oceans onto land?

Ocean water evaporates to form gaseous water and moves into the atmosphere, where it condenses into liquid water and falls out of the atmosphere to land as rain.

Which aquifer listed below would be the most effective in purifying polluted groundwater, and why?

Permeable sandstone; the pores between grains are large enough to let water through but small enough to block contaminants

According to the hydrologic cycle, once precipitation has fallen on land, what paths might the water directly take? Choose all that apply.

Runoff into a river Infiltration into the ground Runoff into the sea Evaporation/transpiration

Why doesn't sea level drop even though oceans have a higher rate of evaporation than precipitation?

Surface water running off into the oceans makes up the difference between evaporation from the oceans and precipitation into the oceans, creating a balance.

What would happen to atmospheric water if Earth were mostly covered with land?

The atmosphere would contain less water.

An agricultural company purchased a large tract of land adjacent to your property and built a group of large commercial greenhouses on it. This company uses a lot of water to keep the plants green and healthy. During a particularly dry summer, the amount of water available to your well starts to decrease. Since you are utilizing the same aquifer, what has this company done to the water supply?

The company has compromised the aquifer and is essentially mining the water from it.

When considering the movement of water on Earth within the hydrologic cycle, which of the following choices is responsible for driving this process?

The hydrologic cycle works because water exists on Earth in solid, liquid, and gaseous states.

La Cañada Alamosa is a tributary of the Rio Grande, located in central New Mexico. Due to climatic changes, the local base level for this stream was lowered. This occurred many times as evident by the presence of multiple terraces. Rounded gravels present on the terraces represent former channel deposits. Using the following photos, classify the observations according to whether they are "true," or " false."

True At least two episodes of downcutting have occurred. Rounded gravels provide evidence that these flat-topped features are terraces. False Only one terrace is present at La Cañada Alamosa. The local base level for this stream is sea level.

Which of the following best describes how geysers erupt?

With a slight reduction in pressure, water in a saturated, natural conduit suddenly boils, sending a plume of steam and hot water into the air above the vent.

What is a floodplain?

a flat surface next to a river channel

In 2011 snow melt and heavy rains in the upper Missouri River drainage basin produced record runoff that led to extensive flooding in lower Missouri River valley, despite the construction of numerous large flood control dams built on the river in the mid 20th century. What type of failure in an artificial flood control system is this an example of?

a flood outside the design capabilities of the dam system overwhelmed the capacity of the reservoirs forcing opening of flood gates, exacerbating the downstream impact of the flooding

Which of the following is associated with areas of karst topography?

caverns soluble rock sinkholes all of these

Complete this analogy: Bouncing is to sand as suspension is to_____________.

clay

Water in the hydrologic cycle readily moves from the land to the oceans through several pathways. How does the vast majority of water get from the ocean to the land surface?

clouds and precipitation

What stream characteristic is measured by the size of the largest particle that a stream can move?

competence

Gradients usually ________ downstream in a major river system.

decrease

Incised meanders and terraces are __________.

erosional features

If a well is drilled into an aquifer where the pressure surface is both above the aquifer and the ground, a __________ is formed.

flowing artesian well

In terms of freshwater storage, groundwater is second only to which of the following sources?

glaciers

Complete this analogy: Sliding is to gravel as dissolution is to_____________.

ions

Caves most commonly form in ________.

limestone

Karst topography is most commonly associated with areas underlain by ________.

limestone formations

Which of the following choices does not directly affect stream velocity?

location of the drainage divide

What type of stream is associated with the formation of an oxbow lake?

meandering stream

The depth below groundwater is the water table. Also, the structure and arrangement of rocks can affect the way groundwater flows. Which of the following can control groundwater's ability to flow? Select the two that apply.

pores/fractures in the rock change of water table elevation

Where is the majority of liquid freshwater found?

rocks and sediments

How can pieces of rock in contact with a stream bed move?

rolling, sliding, bouncing

Which of the following are part of the bed load? CHOOSE ALL THAT APPLY.

sand gravel

A(n) ________ is a circular to elliptical, closed depression in karst areas.

sinkhole

Which of the following is the correct definition of stream gradient?

the drop in elevation of a stream divided by the distance the water travels

The quantity of groundwater that can be stored within sedimentary material is most directly controlled by which of the following parameters?

the porosity of the material

The release of water vapor to the atmosphere by plants is called ________.

transpiration

An artesian system is present when groundwater __________.

under pressure rises above the aquifer level

Which processes result in the widening of the floodplain of a meandering stream?

undercutting and lateral erosion

Downcutting (also known as rejuvenation) of a stream may be due to ________.

uplift of land

When a stream is in a v-shaped valley running on bedrock, the stream is ________.

well above base level

When will a cone of depression stop enlarging?

when the amount of water flowing toward the well equals the amount of water being pumped out of the well

When might a well, Well A, go dry?

when the cone of depression of a second well intersects the deepest part of Well A

A V-shaped valley and no floodplain indicate a ________ stream.

youthful, downward cutting

The Goosenecks of the San Juan River are located in southeast Utah. At this location, the San Juan River has cut a gorge through at least 1,000 feet (300 m) of Paleozoic sedimentary rocks. As mentioned in the video, this region was affected by uplift of the Colorado Plateau during the Cenozoic era. Base level was lowered and this river began to incise downward due to a steepened gradient. A raft on the San Juan would float more than 6 miles to match a crow flying straight for 1.5 miles above this landscape. The Google Earth image and photo below, which depict the same location from different angles, show two features, labeled A and B, that were created by downcutting of the San Juan River. Choose the correct pair of terms from the choices below.

A) incised meanders, B) terraces