Freshwater Use and the Hydrologic Cycle

Question 1

Give the % of Earth’s freshwater and the % of freshwater that is easily accessible for human use.

Answer 1

Less than 2.8% of Earth’s water is freshwater, and less than 1% of that is easily accessible for human use.

Question 2

Explain where most accessible water comes from globally, and where Vancouver’s water supply comes from.

Answer 2

Most accessible water comes from renewable resources, replenished through the hydrologic cycle such as freshwater lakes, rivers, and reservoirs.
In Vancouver, water supply is sourced from three watersheds: Capilano, Seymour, and Coquitlam.

Question 3

Label the natural hydrologic cycle with respect to the stores of Earth’s water and the main processes that move water through the cycle.

Answer 3

The hydrologic cycle is a model that explains the movement of water between Earth’s spheres. It involves stores (reservoirs) and processes (flows) that describe water’s movement.
Evapotranspiration is the main way water moves through the water cycle (energy from the sun and gravity—sun causes liquid water—water vapor

Question 4

Give at least two examples of ways in which human actions can alter the natural hydrologic cycle.

Answer 4

Human actions can alter the natural hydrologic cycle, such as through water extraction, dam construction, and deforestation.

Question 5

Identify and give an example of the three causes of major regional trends in freshwater storage.

Answer 5

Climate change (glaciers melting), Human activity, natural availability
These trends result from factors like changes in precipitation, evaporation, and land use, leading to shifts in freshwater availability.

Question 6

Identify the control variable and planetary boundary for global freshwater use as suggested in 2015.

Answer 6

The control variable for global freshwater use is the maximum amount of consumptive freshwater use (km3/yr), with a planetary boundary of 4000 km3/yr.

Question 7

Describe the four Earth system functions of water, and discuss how they link to the six proposed sub-boundaries for freshwater use in 2020.

Answer 7

Hydroclimatic regulation, hydrogeological regulation, storage, and transport.