The Good Earth - Chapter 12
Arsenic is present in nearly all groundwater in Bangladesh. The water quality standards for arsenic in the country are _____ parts per billion, whereas the standard set by the World Health Organization is 10 parts per billion.
50
What is a point source of groundwater contamination?
A source that can be isolated, specifically identified, and shut down.
What is a nonpoint source of groundwater contamination?
A source that cannot be isolated and originates from a wide region
In the process of lithification, or turning unconsolidated sediment into rock, what two processes reduce the porosity of the material?
Consolidation and Cementation
Observe the pie chart. Match groundwater uses in the United States (2015) to the color and percentage representing the quantity for that purpose.
Green, 68% - Irrigation Red, 7% - Other Blue 4% - Domestic Purple 18% - Public supply Tan, 3% - Industrial
What is the effect called when water is pumped from an aquifer made of unconsolidated material and the total volume of the sediment decreases as the pores collapse?
Ground subsidence
Where is groundwater located?
Groundwater exists in tiny spaces between mineral grains or in cracks.
Which of the following statements is true regarding the relationship between porosity and permeability for earth materials?
High porosity materials can have low permeability when pore spaces are not well connected to each other.
Is the Bangladesh water quality standard for arsenic set at 50 parts per billion (ppb) higher, lower, or about the same as the standard set by the World Health Organization (WHO)?
Higher; the WHO standard is 10 ppb.
Under what circumstances did arsenic become a problem in drinking water wells in Bangladesh?
In the 1970s, the United Nations provided materials for 1 million wells, the use of which became very popular and expanded.
A gaining stream _______ an aquifer.
Is recharged by
What is the specific retention of a material?
It is the amount of water stuck to grains that is not able to flow though the material.
In a consolidated sediment with good porosity, what must the structure of the rock be like for permeability to also be good?
Pore spaces must be connected so that water can flow through the material.
What measure is used to describe the ratio of empty space to grain material in a rock or sediment layer?
Porosity
________ is the proportion of a material such as sand that consists of empty space.
Porosity
Could the current situation of high arsenic levels in drinking water wells in Bangladesh have been avoided?
Possibly, the groundwater could have been tested, but treatments options were limited.
Aquifers require high porosity and permeability to sustain pumping groundwater. What material would be a medium with the highest porosity for an aquifer?
Sand
If wells are pumped faster than the aquifer can recharge them, what consequence could be expected?
Shallow wells may run dry A cone of depression may form The ground may subside as aquifer materials collapse
Wells that are pumped at a high capacity tend to form a cone of depression around the well. What impact might this have on surrounding wells?
Shallow wells may run dry as the water table depth increases.
Which forms or patterns of precipitation will recharge an aquifer most efficiently?
Slow, steady rainfall
A _________ form(s) where the water table intersects with the ground surface.
Spring Wetland
Which of the following are common sources of groundwater?
Stored, ancient waters Stream recharge Precipitation recharge
What government program was established in 1980 with the purpose of cleaning up sites contaminated with hazardous chemicals left by companies that were out of business or were unknown.
Superfund Program
What two processes or aquifer characteristics must be present for an aquifer to experience overdraft?
The amount withdrawn exceeds aquifer recharge. Groundwater is extracted.
Observe the image of a consolidated sediment. Describe the permeability of the material.
The pore spaces are not interconnected, so water would be trapped and permeability would be low.
What shape is a water table?
The water table rises and falls with the elevation of the land.
Which of these materials tends to have the highest porosity?
Unconsolidated earth materials
Where is groundwater located?
Under Earth's surface in rocks and unconsolidated materials.
A barrier to groundwater flow made of a low-permeability material such as clay, shale, or unfractured igneaous rock is an ________.
acquitard
What do we call permeable materials that yield significant quantities of water?
aquifers
Aquifers are contained in permeable materials with moisture levels that ________.
are saturated and yield significant amounts of water
Why are losing streams common in arid regions?
arid soils with high-permeability banks and streams allow water to leave easily.
Most groundwater is located __________.
between mineral grains in rocks and sediments.
Lithification, the process of converting sediment to rock, reduces porosity as compaction collapses air-filled spaces and ________ fills remaining spaces with agents that hold the grains together.
cementing
An aquifer that has an aquitard above and below the groundwater is an __________ aquifer.
closed
In an aquifer that has been pumped more than it can naturally recharge is a ___________.
cone of depression
Observe the image and the groundwater flow paths. What kind of stream is shown?
gaining stream
When groundwater is removed from unconsolidated material and the grains compact as water is extracted from pore spaces, a decrease in volume of the sediment called ___________.
ground subsidence
Water below Earth's surface that is present in rocks or unconsolidated sediment is called __________.
groundwater
Wetlands are unique features that form where ______.
groundwater intersects with the ground surface
In arid regions where stream banks and stream beds are made of high-permeability materials, the streams are often _______ streams.
losing
An aquitard is a __________ and commonly is made of clay, shale, or unfractured rock.
low-permeability layer that slows groundwater flow
Groundwater arsenic contamination is the US ________.
may affect an estimated 13 million people
An earth material with high porosity _________.
might have high permeability if the pore spaces are well connected
Slow, steady rainfall and slow snowmelt recharge an aquifer _______ intense, heavy rainfall and fast snow melt.
more efficiently than
Groundwater contamination that comes from a wide region and cannot be traced to a single source is called a __________.
non-point source
Groundwater arsenic contamination in the US ________.
occurs in conjunction with igneous and metamorphic rocks may be made worse through mining activities
When groundwater is extracted, or pumped, more quickly than the aquifer can naturally recharge, the effect is called groundwater __________.
overdraft
Groundwater contamination that can be directly identified and isolated is called a ___________.
point source
Aquifers are recharged by _________ from long ago.
precipitation streams glacial meltwater
A cone of depression is an increase in water table depth around a well due to _______.
pumping that exceeds the rate of recharge in the aquifer
The amount of water that is trapped and stuck to grains of sand or clay and is unable to flow though the material is called the specific ____________ of the material.
retention
Where would the water table be higher - under a hill or in a nearby valley?
under the hill