4. Water Cycle
§ Elements of the
Water Cycle
-Landscape processes
-Sediment transport
-Carbon/nutrient cycling
-Species ecology 9.
-Large-Scale Atmospheric circulation in the
tropics
-Intertropical Convergence Zone
-Band of convective clouds and thunderstorms, providing much of the Amazon's
water 10.
-Hadley
Circulation
-An average thermal circulation that consists of warm air rising
at the equator, moving poleward, then descending at the poles and moving
equatorward near the
surface.
§ Hydrologic Cycle
-Evaporation
-Evapotranspiration
-potential evapotranspiration (PE). This is the greatest amount of water
vapour which could be diffused into the atmosphere given unlimited supplies
of water. 13.
-Probable that Amazonas regions which have higher rainfall and a wet canopy
tend to have average evaporation rates greater than potential rate. 12.
-Rainforest located near equator, sun's rays hit earth directly
-Evapotranspiration =>Sun's energy creates winds and air currents to spread
warmth from Amazon
-Deforestation =>less rain from Atlantic, rainforest permanently drier
-Less heat spread out by Amazon
-Amazon overheated
-May affect global climate
-Evapotranspiration from forest compared to that of crops/plantations/pastures
may not be that much greater
-Pastures transpire much less water
-Much warmer mean surface temperatures 4. ., 6.
-Energy attracted from ocean is capable of enhancing evaporation of intercepted
water 12.
-Strong influence from western Pacific's sea
surface temperatures on rainfall, even though moisture has to travel over
Andes Mountains
Rainfall pattern in eastern equatorial Amazon extremely sensitive
to temperature changes on sea surface
-Sea surface temperature increased,
drought conditions appear
-Sea surface temperature decreased,
floods result 22.
-During
course of evaluating wet/dry canopy evaporation differences between forest
and grassland in the Amazonas, "...a poorly managed land-use change would
exacerbate this difference. Soil compaction and destruciton of surface
macropores during deforestation could dramatically reduce infiltration and
increase surface runoff, thereby generating soil erosion and nutrient loss
and reaching the resilience and persistence of the ensuing grassland in dry
months...".
-Shuttleworth, 12.
-Rainfall
-Half thought to come from evapotranspiration
-Drier regional climate
-Some rainfall may come from water vapor from Atlantic
-No concrete data on effect of deforestation on rainfall
-Highly variable, even before large deforestation acts 4.,6
-Soil conductivity
-K* or Ks
-At surface, measure of overland flow
-In subsoil, meaurement of saturation
-Storm Runoff:
1)Hortonion overland flow: rainfall exceeds infiltration capacity of
basin. Major cause of rapid rise of river flow levels, prime cause of
soil erosion in some cases. No movement of underground water.
Unusual in humid temperature regions where rainfall intensity is generally
low and vegetation cover encourages infiltration.
2)Saturation overland: soil is saturated, water-table has come to surface.
Occurs in small valleys in humid climates, on land bordering streams, in
hillside hollows with high water-tables, and where soil moisture levels are
high.
3)Subsurface stormflow 13.
-Cloud condensation nuclei
(CCN)
-Linked to radiative forcing, precipitation, and cloud structure
-CCN very low during wet season
-Resembled concentrations more typical of marine locations (low CCN) than
most continental sites (high CCN)
-At low CCN concentrations, cloud properties more sensitive
**enhanced aerosol emmisions due to human activity in Amazon Basin may have
stronger impact on climate than emmisions in other continental regions.
-Little research done on CCN in the tropics
-Modeling studies suggest increased CCN concentrations in the tropics
change altitude and mechanism of rain production
-Large scale atmospheric circulation 18.
-Acid Rain
The
pH's of the Amazon river can be characterized by different water types of
Amazon river water. Three types and their relative pH's are whitewater-alkaline
to neutral pH, blackwater-usually acidic, and clearwater-acidic to alkaline.
Acid rain is really "acid depostion" from the atmosphere.
There are 2 types of acid deposition: wet and dry. According
to the EPA, "Wet deposition refers to acidic rain, fog, and snow. As this
acidic water flows over and through the ground, it affects a variety
of plants and animals. The strength of the effects depend on many
factors, including how acidic the water is, the chemistry and buffering
capacity of the soils involved, and the types of fish, trees, and
other living things that rely on the water.
Dry deposition refers to acidic gases and particles.
About half of the acidity in the atmosphere falls back to earth
through dry deposition. The wind blows these acidic particles and
gases onto buildings, cars, homes, and trees. Dry deposited gases
and particles can also be washed from trees and other surfaces by
rainstorms. When that happens, the runoff water adds those acids
to the acid rain, making the combination more acidic than the falling
rain alone."
Many organisms cannot tolerate high
levels of acidity, and even those who can, their food sources (such as insects)
may not. As acidity in a water system increases, the number and diversity
of organisms decreases. Also, when acid rain flows through soils in
a watershed, aluminum is released into the watershed, which is toxic to
fish. At levels of pH5, most fish eggs cannot hatch.
Again, from the EPA: "The impact of nitrogen
on surface waters is also critical. Nitrogen plays a significant
role in episodic acidification and new research recognizes the
importance of nitrogen in long-term chronic acidification as well.
Furthermore, the adverse impact of atmospheric nitrogen deposition on
estuaries and near-coastal water bodies is significant. Scientists
estimate that from 10-45 percent of the nitrogen produced by various
human activities that reaches estuaries and coastal ecosystems
is transported and deposited via the atmosphere. For example, about
30 percent of the nitrogen in the Chesapeake Bay comes from atmospheric
deposition. Nitrogen is an important factor in causing eutrophication
(oxygen depletion) of water bodies. The symptoms of eutrophication
include blooms of algae (both toxic and non-toxic), declines in
the health of fish and shellfish, loss of seagrass beds and coral
reefs, and ecological changes in food webs."
§ Water Cycle and
Life on Land
-Deep rooted trees able to access soil moisutre during extended dry periods,
whereas shallow rooted ground cover is under stress. Removal of trees
prevents additional water losses at these times. 12.
§ Human Impacts
(besides hydroelectric power
-Cloud condensation nuclei (CCN)
The Massachusetts Institute of Technology
Contact: lacooney@mit.edu
_______________________________________________________________________________________________________________________________________________________________
Research Bibliography
***Note: I will update these web-sites as correct bibliographical
entries soon.
1. Palaeoceanography
Environmental Change Research Centre
2. Land Surface
Hydrology and Water Chemistry The Large Scale Biosphere-Atmosphere Experiment
in Amazonia (LBA)
3. The source
of the Amazon River was just recently discovered. Why did it take so long?
National Geographic Society
4. Tropical
Deforestation Fact Sheet NASA Earth Observatory
5. Effects of
Deforestation
6. Amazonia
- Resiliency and Dynamism of the Land and its People Nigel J.H.
Smith, Emanuel Adilson S. Serrão, Paulo T. Alvim, and Italo C. Falesi,
United Nations University
7. Solving the Amazon?s climate
riddle By Ginger Pinholster, SCIENCE
8. Fish in the Trees
by Rachel Hauser, NASA Earth Observatory
9. River Seasons
by Laura Cheshire, NASA Earth Observatory
10. http://www.gsfc.nasa.gov/gsfc/educ/science/2001/01-04-01.htm
11. Amazon
Deconstruction: Cause and Effect camille, charlie,
hsing hsing, maya, pete, University of Washington
12. "Applications of Hillslope
Process Hydrology in Forest Land Management Issues: The Tropical North-East
Australian Experience", Mike Bonell
13. Dictionary of Geography, Oxford University Press
14. "WATER RESOURCES MANAGEMENT
FOR ENERGY GENERATION PURPOSES IN STREAMS PRESENTING STRONG SEASONAL FLOW
VARIATIONS - PLANNING ASPECTS",
Bela Petry & Doron Grull
15. "Analysis of
the Streamflow Record Extension for the Xingu River at Babaquara Maria
Elvira Pineiro Maceira and Jorge Machado Damazio
16. Seasonal Variations
in the evapotranspiration of a transitional tropical forest of Mato Grosso,
Brazil George Vourlitis, Nicolau Priante Filho, Mauro Hayashi,
Jose de S. Nogueira, Fernando Caseiro, Jose Holanda Campelo
17. Towards improving
natural resources use in Eastern Amazonia through a modified sequential
agroforestry system Sa, T.D. de A.; Vielhauer, K.; Kanashiro,
M.; Denich, M. and Vlek, P.L.G.
18. Cloud condensation
nuclei in the Amazon Basin: "Marine" conditions over a continent?
Gregory C. Roberts and Meinrat O. Andreae; Jingchuan Zhou; Paulo
Artaxo
19.
Rates and Processes
of Amazon Deforestation Michael Glantz, Tandy Brook, Patricia
Parisi
20.
Acid Rain
Environmental Protection Agency (EPA)
21.
Effects
of Acid Rain: Lakes and Streams EPA
22. Sea
surface temperatures impact weather in Amazon basin Environmental News
Network, By Robinson Shaw
The Massachusetts Institute of Technology
Contact: lacooney@mit.edu