Team Ecology

Biogeochemical cycling: Global water cycle

Kasey Barton

Carolyn Bergstrom

Fenny Cox

Don Drake

Oceana Francis

David Tallmon

Chris Tubbs

Goals: For students to understand the water cycle, including:

1. Understand relative sizes of pools and fluxes of H20 cycle.

2. Understand how human activities affect pools and fluxes of H20 cycle.

3. Appreciate ethical consequences of human effects on H2O cycle.

Biogeochemical cycling: Global water cycle

Outcomes:

1. Predict how several human activities will alter the H20 cycle (qualitative/quantitative).

2. Assess the global ethical implications of human impacts on H20 cycle.

Biogeochemical cycling: Global water cycle

pools = 1000’s km3, fluxes 1000’s km3/yr

Global water cycle

Rain falling on a tropical rain forest can be lost via three paths:

1. evaporation2. transpiration (water from soil → atmosphere via plants)3. runoff & groundwater

Rank the paths in order of magnitude from greatest → least amount of water lost.

A. 1 > 2 > 3B. 1 > 3 > 2C. 2 > 3 > 1D. 2 > 1 > 3E. 3 > 2 > 1

http://guernseysoil.blogspot.com/2012/07/your-backyard-woods-water-cycle.html

Figure not to scale

Rain falling on a tropical rain forest can be lost via three paths:

1. evaporation2. transpiration (water from soil → atmosphere via plants)3. runoff & groundwater

Rank the paths in order of magnitude from greatest → least amount of water lost.

C. 2 > 3 > 1

48% transpiration36% runoff & groundwater16% evaporation

Globally, 2/3 of water flux from land → atmosphere is via transpiration.

http://guernseysoil.blogspot.com/2012/07/your-backyard-woods-water-cycle.html

pools = 1000’s km3, fluxes 1000’s km3/yr

Global water cycle

What human activities might affect the water cycle?

With your group, discuss the main effects that either deforestation or global warming will have on the global water cycle.

Include changes in fluxes and pools.

‘Modify’ your large handout template with colored post-its: blue for increase, red for decrease.

Tape your template to wall.

+ -

pools = 1000’s km3, fluxes 1000’s km3/yr

Global water cycle

1. What could we do to make this scenario more realistic?2. What is the scale of deforestation?3. What is the scale of global warming?4. Model how these two activities simultaneously affect the

water cycle5. What are the ethical implications of human effects on the

water cycle? Where do these activities occur, and who is affected?

Summative assessment: take-home exam