Review the literature on a relevant topic

1
What You Will Do?

• Review the literature on a relevant topic
• Prepare a 20-30 minute presentation for the class
  and lead a discussion
• Address a knowledge gap or unresolved problem in
  the published research
• Use published data and/or findings
• Use readily available data
• Use any data you can find

2
Class Time
Ecohydrology
Ecohydrology

• Open with a presentation
• Include background summary
• Identify knowledge gaps and/or unresolved issues
• Occasionally we will have a guest speaker
• Discussion and brainstorming
• Introduce the next classs topic and distribute
  relevant reading
• We may sometimes decide to continue with the
  current topic if ideas are ripe

3
Out of Class
Ecohydrology
Ecohydrology

• Review your topic of choice
• If possible, create an Endnote library
• Develop a Powerpoint presentation
• Review the suggested papers for the upcoming
  class
• Review the suggested papers for the upcoming
  class
• Tackle a project-problem I encourage groups on
  this.

4
An Example Evapotranspiration
Ecohydrology
Ecohydrology

• Pan evaporation rates have been decreasing for at
  least the past 50 years
• Why?
• Two primary theories exist
• Brutsaert and Parlange say ET is increasing and
  this leads to decreasing pan evaporation
• Roderick and Farquar say incoming solar radiation
  is decreasing, which leads to reduced PET

5
Some Suggested Papers

• Brutsaert, W. and M. B. Parlange, 1998
  Hydrologic cycle explains the evaporation
  paradox. Nature, 396, 30.
• Roderick, M. L. and G. D. Farquhar, 2002 The
  cause of decreased pan evaporation over the past
  50 years. Science, 298(5597), 1410-1411.
• OTHER PAPERS
• Milly, P. C. D. and K. A. Dunne, 2001 Trends in
  evaporation and surface cooling in the
  Misssissippi River basin. Geophysical Res. Let.,
  28(7), 1219-1222.
• Peterson, T. C., V. S. Golubev, and P. Y.
  Groisman, 1995 Evaporation losing its strength.
  Nature, 377(6551), 687-688.

6
Brutsaert and Parlange (1998), Nature
a1Ep
E (when wet)
Ep
7
Brutsaert and Parlange (1998), Nature
E (when dry)
Eo-DH
a1Ep
EoDH
Ep
8
Brutsaert and Parlange (1998), Nature
a1Ep
?EEo-DH
Ep
9
Brutsaert and Parlange (1998), Nature
a1Ep
?EEo-(Drv)
a2l(Drv)
Ep
10
Roderick and Farquar (2002), Science
a1Ep
Ep
11
Roderick and Farquar (2002), Science
a1Ep
?Epa2Rn

• Increased clouds and atmospheric aerosols
• Decreased daily temperature range
• DRn -315 MJ/yr

Ep
12
What about actual ET?

• Can we conceive a conceptual model that resolves
  this issue?
• Are there any readily available data that cast
  insights?

13
Proposed Model
Annual hydrologic budget
14
Data Analysis
Annual hydrologic budget ET P - Q
15
Data Analysis
Data Sources Annual Precipitation U.S. Climate
Division data N. B. Guttman and R. G. Quayle,
Bulletin of the American Meteorological Society
77, 293 (1996) (also, the Northeast Regional
Climate Center - NRCC or National Climate Data
Center - NCDC) Annual Streamflow U.S.
Geological Survey http//waterdata.usgs.gov/nwis/s
w
16
Data Analysis
Annual Precipitation (mm/yr)
17
Data Analysis
Annual Precipitation (mm)
Annual Stream Discharge (mm)
18
Data Analysis
slope 1.05 mm yr-1
Annual Precipitation - Discharge (mm)
19
Model and Published Literature
Annual hydrologic budget
20
Whats Missing?

• Need to resolve the flow parameter, a
• Attempt a sexier analytical solution to the
  equation
• Changes in extent of vegetation cover and
  vegetation type
• What about non-steady state?
• Compare model to data

21
Model and Published Literature
Annual hydrologic budget
1950 PET 2.87 m/yr 2000 PET 4.29 m/yr