Geoscience Reference
In-Depth Information
some scale to the impact of large atmospheric
nitrogen inputs, Löye-Pilot
et al
. (1990) estimate
that atmospheric nitrogen input into the
Mediterranean Sea is of the same order of magnitude
as the riverine input. It is estimated that 25 per cent
of nitrogen inputs to the Baltic Sea come from the
atmosphere (BSEP, 2005).
averaged precipitation value (including
surrogate measures).
4
Why is scale such an important issue in
the analysis of precipitation in
hydrology?
5
Describe a field experiment (including
equipment) required to measure the
water balance beneath a forest
canopy.
SUMMARY
6
Discuss the role of spatial scale in
assessing the importance of a forest
canopy within a watershed.
Precipitation is the main input of water within a
catchment water balance. Its measurement is
fraught with difficulties and any small errors will be
magnified enormously at the catchment scale. It is
also highly variable in time and space. Despite these
difficulties precipitation is one of the most regularly
measured hydrological variables, and good rainfall
records are available for many regions in the world.
A forest canopy partitions rainfall into components
that move at different rates towards the soil surface.
The nature of the canopy (leaf size distribution and
leaf area index) determines the impact that a canopy
has on the water balance equation.
Analysis of rainfall can be carried out with respect
to trying to find a spatial average or looking at the
intensity and duration of storm events. Although
there are techniques available for estimating
precipitation their accuracy is not such that it is
superior to a good network of precipitation gauges.
FURTHER READING
Bailey, T.C. and Gatrell, A.C. (1995)
Interactive
spatial data analysis
. Longman, Harlow.
Gives a modern view of spatial analysis, not
necessarily just for precipitation.
Barry, R.G. and Chorley, R. (2003)
Atmosphere,
weather and climate
(8th edition). Routledge, London.
Explains the principles of precipitation generation
well.
Cheng, M. (2003)
Forest hydrology: an introduction to
water and forests
. CRC Press, Boca Raton, Florida.
A more modern text than Lee (1980) which gives a
good overview of forest hydrology.
ESSAY QUESTIONS
Lee, R. (1980)
Forest hydrology
. Columbia University
Press, New York.
A classic text giving an excellent overview of
forest hydrological processes.
1
Describe the different factors affecting
the spatial distribution of precipitation
at differing scales.
Strangeways, I. (2006)
Precipitation: theory,
measurement and disribution
. Cambridge University
Press.
A modern text on precipitation processes and
measurement.
2
How are errors in the measurement of
rainfall and snowfall minimised?
3
Compare and contrast different
techniques for obtaining a spatially
