Groundwater Flashcards
1) Which of the following materials is most readily dissolved by water?
A) Clay minerals
B) Silica
C) Feldspars
D) Calcite
D) Calcite
Calcite is a form of calcium carbonate (CaCO₃), and it is highly soluble in water, especially in the presence of slightly acidic conditions (e.g., rainwater, which contains dissolved carbon dioxide). When water comes into contact with calcite, it dissolves the mineral and forms calcium ions (Ca²⁺) and bicarbonate ions (HCO₃⁻).
2)To be a gaining stream, the elevation of the water table must be ________ than that of the
surface of the stream.
A) lower
B) higher
C) heavier
D) lighter
B) higher
A gaining stream is one where water from the groundwater system flows into the stream, increasing the stream’s discharge. For this to happen, the elevation of the water table (the upper surface of the saturated zone of groundwater) must be higher than the elevation of the stream surface.
3) Which of the following materials would make the best aquifer?
A) Gravel
B) Sandstone
C) Clay
D) Gneiss
A) Gravel
An aquifer is a geological formation that can store and transmit water effectively. To function as a good aquifer, the material needs to have both porosity (the ability to store water) and permeability (the ability to allow water to flow through it).
4) Why is the aquitard a necessary part of any groundwater system?
A) It absorbs excess water, thus keeping the aquifer from overflowing
B) It prevents water from reaching the aquifer, thus allowing it to be retained at the surface
C) It serves like the bottom of a bucket, allowing water in the aquifer above to be held in place.
D) It stores groundwater, and is thus a critical part of the zone of saturation
C) It serves like the bottom of a bucket, allowing water in the aquifer above to be held in place.
An aquitard is a layer of rock or sediment that is relatively impermeable (or has very low permeability) and prevents or restricts the movement of groundwater. It acts as a barrier that confines water in an underlying aquifer, preventing it from escaping. This is why the aquitard is often referred to as the “bottom of a bucket” — it holds the water in place within the aquifer above it, much like a sealed container.
5) A water tower sending water into your home is most like a ________ artesian well and if
your pipes were not sealed ________.
A) flowing; water would flow out of them
B) flowing; water would sink back into the aquifer
C) nonflowing; water would flow out of them
D) nonflowing; water would sink back into the aquifer
A) flowing; water would flow out of them
A water tower works in a similar way to a flowing artesian well. In an artesian well, water is naturally pressurized due to the surrounding rock layers, causing it to flow to the surface without the need for pumping, as long as the well is properly tapped. Similarly, a water tower uses gravity to create pressure in the pipes, allowing water to flow into your home. The pressure from the tower pushes the water through the pipes, so when you turn on a tap, water flows out.
6) Why do geysers spout periodically and then go quiet?
A) Large rainstorms overflow underwater chambers, producing steam
B) Magma varies between very hot and less hot, thus causing geyser eruptions to come and go.
C) Steam builds up in empty chambers and is released, thus relieving pressure
D) Steaming water tends to contract, crushing rocks
C) Steam builds up in empty chambers and is released, thus relieving pressure.
Geysers erupt periodically due to the buildup of pressure from steam in an underground chamber. Here’s how it works:
Water enters the geyser’s underground reservoir: Rainwater or groundwater seeps down into the hot underground chambers near magma or hot rocks.
Water heats up: As the water comes into contact with hot rocks or magma, it heats up and turns into steam. However, because of the high pressure at depth, the water doesn’t immediately turn to steam.
Pressure builds up: Over time, the steam pressure builds up as the water continues to heat. Eventually, the pressure becomes too much for the surrounding rocks to contain.
Eruption: When the pressure is finally released, the steam rapidly escapes, causing the geyser to erupt. The eruption can last anywhere from seconds to several minutes, depending on the geyser.
Quiet period: After the eruption, the geyser goes quiet as the underground chambers refill with water, and the cycle begins again.
7) California’s Central Valley is an important agricultural area for U.S. fruit and vegetable
production. Because of the semiarid climate there, farmers must irrigate their crops. Which
environmental problem do you anticipate as a result?
A) Saltwater contamination
B) Fluvial erosion
C) Land subsidence
D) Water acidification
C) Land subsidence
In areas like California’s Central Valley, where farmers rely heavily on irrigation in a semiarid climate, land subsidence is a significant environmental problem. Here’s why:
Land subsidence occurs when the ground level sinks due to the over-extraction of water from underground aquifers. In California, much of the irrigation is sourced from groundwater, which causes water levels in aquifers to drop. When the water is pumped out faster than it can be replenished, the ground can compact, leading to subsidence.
This process can damage infrastructure, reduce the capacity of aquifers to store water, and make the land less suitable for farming in the long term.
8) 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?
If all rain were to cease, the water table would gradually lower as groundwater is depleted without replenishment. As a result, the undulations in the water table would become less pronounced and more subdued, eventually smoothing out over time due to the lack of new water entering the system.
9)Match the word with the correct definition.
A) Rock or regolith that can store and transmit water and receives its recharge directly from the
atmosphere
B) Rock or regolith that can store and transmit water but is contained between two
impermeable layers
C) Dividing line between the vadose zone and the zone of saturation
Words: water, confined aquifer, unconfined aquifer
A) Rock or regolith that can store and transmit water and receives its recharge directly from the atmosphere
Word: Unconfined aquifer
B) Rock or regolith that can store and transmit water but is contained between two impermeable layers
Word: Confined aquifer
C) Dividing line between the vadose zone and the zone of saturation
Word: Water table
Explanation:
An unconfined aquifer is directly recharged by rainwater or surface water, and there is no impermeable layer above it.
A confined aquifer is bounded by impermeable layers above and below, which limits the movement of water into or out of it.
The water table is the boundary between the vadose zone (unsaturated zone) and the saturated zone, where all the pores in the rock or soil are filled with water.
