Sierra Nevada

Question 1

What is the difference between permeability vs. porosity?

Answer 1

Permeability: ability to allow water to flow through rock

Porosity: refers to ability to store water within holes (pores) within rock

Question 2

What is a confined aquifer?

Answer 2

• Water is stored in porous rock surrounded by impermeable rock
• Means water can’t flow away or aquifer be replenished

Question 3

What is an unconfined aquifer?

Answer 3

• Porous rock surrounded by permeable
• means water can percolate and flow out of aquifer

Question 4

What do the Rockies act as?

Answer 4

• a watershed (AKA drainage basin)
  
  • Colorado River basin flows into West -> Mexico
  • Great Plains basin is in East
    
    • Includes Ogallala Aquifer

Question 5

What inputs are there into river basins?

Answer 5

• Rainfall (convectional or frontal)
  
  • Location determined by proximity to ocean (frontal) or topography (convectional)
    
    • eg. Mountains create rain shadows
• Rocky Mountain snowpack meltwater feeds river seasonally

Question 6

What affects the output from river basins?

Answer 6

• Level of interception (may vary due to extent of deforestation)
• Level of runoff
  
  • eg. Caliche in Great Plains reduces infiltration
• Geology
  
  • Only unconfined aquifers will be replenished

Question 7

What are the reasons for variation in hydrological balance of river basins?

Answer 7

• Anthropogenic:
  
  • Eg. Human extraction of water from confined aquifers
• Secular: LT climate change (reduction of water in Colorado Basin and Great Plains)
• Periodity:
  
  • Annual, seasonal, monthly, diurnal changes to water flow
• Stochastic:
  
  • random factors eg. localised thunderstorms

Question 8

What is the main input of water into the Colorado River basin?

Answer 8

• Rain from North Pacific Ocean front systems
  
  • cold frontal systems leave snow on the Sierra Nevada
  • Rain shadow effect on east side of SN (Death Valley/Mojave desert)
  • snowmelt during summer provides runoff

Question 9

What is caliche?

Answer 9

• impermeable layer of calcium carbonate on bottom of aquifer
  
  • prevents it from being recharged

Question 10

What has happened to the water table in the Great Plains?

Answer 10

• dropped by 1.5m/yr
  
  • wells have been deepened to access water
• in some places water has been totally drained

Question 11

What sort of aquifer is the High Plains aquifer?

Answer 11

• unconfined
• parts of the aquifer is covered by a caliche layer
• permeability is allowed by playa lakes

Question 12

What are the main uses of water in the Colorado River Basin?

Answer 12

Irrigation:
- 2.1m acres to 15.5m acres in 2015

Question 13

What is grown in the Colorado River Basin?

Answer 13

• wheat (largest in US)
• ethanol
• cotton
• cheese (largest in world)

Question 14

Why is there water insecurity in the Colorado River Basin?

Answer 14

• The High Plains aquifer is unconfined for now
  
  • deterioration of playa soils is increasing though
• region is semi-arid, evaporation rate is high
  
  • steady winds are also present —> evaporation
• increased evaporation is increasing amount of caliche in soil
  
  • making aquifer more confined

Question 15

What are Playa Lakes?

Answer 15

• lakes which have soil that does not contain caliche
  
  • allows for aquifer to be recharged
• farming destroys playa
  
  • creates layer of caliche as soil moisture evaporates

Question 16

What strategies are states using to allow water levels to recover?

Answer 16

• usage of more efficient irrigation systems (centre pivot)
• farmers use more recycled water
• plant crops that use less water (sunflowers)