Geoscience Reference
In-Depth Information
—
Evaporation pans
. The measured evaporation from a sample of water
held in a prescribed container (e.g., the '
Class A
' pan) may be used as an
indication of that from nearby surfaces such as crops and lakes, but
requires correction using an empirical
pan coefficient
in the range 0.3-1.0
(but usually 0.65-0.85).
—
Watersheds and lakes
. Evaporation may be inferred from the measured
water balance of watersheds and lakes, but this is difficult because it is
deduced as a small residual in a water balance in which other terms
dominate, so errors may be 20-30%.
—
Lysimeters
. Evaporation is determined from detailed measurements of
the water balance for a sample of soil and vegetation that is
representative
of its surroundings
, but ensuring this can be a challenge. High quality
weighing lysimeters are considered the (albeit expensive) standard
against which alternatives can be validated.
—
Soil moisture depletion
. The measurements of precipitation and the
change in the soil moisture stored in the soil profile (measured using
neutron probes, capacitance probes, time-domain reflectometers, etc.)
can be used to estimate evaporation.
References
Campbell Scientific (1987)
Bowen Ratio Instrumentation
, Campbell Scientific, Logan, Utah,
online at: http://www.campbellsci.com/documents/manuals/bowen.pdf.
Fairmount Weather Systems (2010) Meldreth, Hertfordshire, UK, online at: http://www.
fairmountweather.com/.
Federer, C.A. & Tanner, C.B. (1966) Sensors for measuring light available for photosynthe-
sis.
Ecology
,
47
, 654-7.
Kipp and Zonen (2010) Delft, The Netherlands, online at: http://www.kippzonen.
com/?category/111/Home.aspx.
LI-COR Environmental (2010) Lincoln, Nebraska, online at: http://www.licor.com/env/
Products/Sensors/200/li200_description.jsp.
McCaughey, J.H. (1981) A reversing temperature-difference measurement system for
Bowen ratio determination.
Boundary-Layer Meteorology
,
21
(1), 47-55.
Shuttleworth, W.J. (1993) Evaporation. In:
Handbook of Hydrology
(ed. D. Maidment),
pp. 4.1-4.53. McGraw-Hill, New York.
