Unit 3-Freshwater Systems

Question 1

Wetlands

Answer 1

• Systems that combine elements of fresh water and dry land
• Extremely rich and productive
• Slows runoff, reduces flooding, recharges aquifers and filters pollutants
Many have been drained and filled for agricultural purposes

Composed of freshwater marshes, swamps, bogs

Question 2

Freshwater marshes

Answer 2

○ Shallow water allows plants to grow above water’s surface

Cattails and bulrushes common in North American marshes

Question 3

Swamps

Answer 3

○ Also contain shallow water rich in vegetation, but occur in forested areas
Can be created when beaver build dams across streams, flooding wooded areas upstream

Question 4

Bogs

Answer 4

Ponds thoroughly covered with thick floating mats of vegetation

Question 5

Lakes and Ponds:

Answer 5

• Bodies of open standing water
Several different zones, since physical conditions and types of life within them vary depending on depth and distance from shore

Question 6

Littoral Zone

Answer 6

§ Region ringing the edge of a water body

§ Water is shallow enough that aquatic plants grow from the mud and reach above the water’s surface
Nutrients and productive plant growth make region rich in invertebrates (larvae. sails, crayfish), provides food for fish, birds…etc

Question 7

Benthic Zone

Answer 7

§ Extends along bottom of entire water body (from shore to deepest point)

§ Many invertebrates live in the mud on the bottom, feeding on detritus (organic matter fragments) or preying on each other
Can be photic or aphotic (can be shallow enough for light to penetrate)

Question 8

Limnetic Zone

Answer 8

§ Open portion of lake or pond, away from the shore

§ Lots of light (in the photic zone), supports phytoplankton, which support zooplankton
□ Phytoplankton and zooplankton are then both eaten by fish

§ Sunlight intensity and water temperature decreases with depth
Clear water allows sunlight to penetrate deeply, turbid water does not

Question 9

Profundal Zone

Answer 9

§ In the aphotic zone (sunlight does not reach here)

Lacks plant life, lower in dissolved oxygen and supports fewer animals

Question 10

Oligotrophic lakes and ponds

Answer 10

• Oligotrophic lakes and ponds have low nutrient and high oxygen conditions, can slowly give way to high nutrient, low oxygen conditions of eutrophic lakes and ponds
Animals living under oligotrophic conditions adapt to eutrophic conditions

Question 11

Ground Water and the Hydrologic Cycle:

Answer 11

• Any precipitation reaching Earth’s surface that does not evaporate, flows into waterways, or is taken up by organisms become groundwater
• Becomes surface water again through springs and wells
• Flows downhill and from areas of high press to low pressure, emerging to join surface water bodies at discharge zones
Groundwater makes up one fifth of the Earth’s freshwater supply

Question 12

Aquifers:

Answer 12

Porous formations of rock, sand, or gravel that hold ground water

Zone of aeration
Zone of saturation
Water table
Recharge zone

Question 13

Zone of aeration

Answer 13

§ Upper layer

Contains pore spaces partly willed with water

Question 14

Zone of saturation

Answer 14

§ Lower layer

Pore spaces completely filled with water

Question 15

Water table

Answer 15

○ Boundary between zone of aeration and zone of saturation known as the water table
Below the water table, all pore spaces are completely filled with water, above the water table, some pater is present in spaces, but the ground is not completely saturated

Question 16

Recharge Zone

Answer 16

Any area where water infiltrates Earth’s surface and reaches an aquifer below

Question 17

Confined aquifer

Answer 17

○ Artesian aquifer
○ Water bearing porous layer of rock, sand, or gravel is trapped between upper and lower layers of less permeable substrate (often clay)
Water is under great pressure

Question 18

Unconfined aquifer

Answer 18

No impermeable upper layer to confine water, so under less pressure and can be readily recharged by surface water

Question 19

Dams:

Answer 19

• Any obstruction placed in a river or stream to block the flow of water so that water can be stored in a reservoir
Used to prevent floods, provide drinking water, facilitate irrigation, and generate electricity

Question 20

China’s Three Gorges Dam:

Answer 20

• World’s largest dam
• Enables boats and barges to travel farther upstream, provides flood control, and generates enough hydroelectric power to replace dozens of large coal or nuclear plants
• Flooded 22 cities, required the largest resettlement project in China’s history
Slows river’s flow so suspended sediment is settling behind dam, causing river downstream to erode away

Question 21

Dikes and Levees:

Answer 21

• Long raised mounds of earth along banks of rivers to hold rising water in main channels

Question 22

Use of Water- Diversion

Answer 22

rerouting of water from its natural river channel by means of built structures

Question 23

Use of water- Channelization

Answer 23

artificial channel modifications, including straightening and concrete lining of channels

Question 24

Use of water- consumptive use

Answer 24

remove water from an aquifer or surface water body and do not return it

Large portion of agricultural irrigation, industrial and residential uses are consumptive

Question 25

Use of water- non consumptive use

Answer 25

does not use, or only temporarily removes water from an aquifer or surface body

i.e. Using water to generate electricity at hydroelectric damns (water taken in, passed through machinery to turn turbines, released downstream)

Question 26

Bottled Water:

Answer 26

• Not necessarily more safe than tap water (usually it is just tap water)
• Fewer checks on bottled water and the bottling process than on municipal water supplies
• Chemicals can leach from the plastic into the water
Take a lot more energy to produce bottled water, negatively impacts sustainability of groundwater withdrawal and lack of protection of source water

Question 27

Transboundary Waterways:

Answer 27

• Bodies of water that cross or flow along national borders

Can cause hostilities among nations

Question 28

Economic Approach to Water Conservation:

Answer 28

• Idea that the price of water should reflect the true cost of its extraction
• Might make water less accessible to the world’s poor, and increase the gap between the rich and poor
Privatization of water supplies has resulted in rural residents paying much more for water than those connected to public supplies

Question 29

Artificial Wetlands:

Answer 29

• Natural wetlands undergo water purification naturally, constructing artificial wetlands helps treat wastewater
• Waste water that has gone through primary treatment is pumped into the wetland, where microbes living amid the algae and aquatic plants decompose the remaining pollutants
Water cleansed in the wetland can be released into waterways