Geoscience Reference
In-Depth Information
vadose zone
Area between the water table and
the earth surface. The soil/rock is normally partially
saturated.
vapour pressure
Pressure exerted within the par-
cel of air by having the water vapour present within
it. The more water vapour is present the greater the
vapour pressure.
vapour pressure deficit
The difference between
actual vapour pressure and saturation vapour pres-
sure.
variable source areas concept
The idea that only
certain parts of a catchment area contribute overland
flow to stormflow and that these vary in space and
time; compare to the partial areas concept.
velocity-area method
A technique to measure
instantaneous streamflow through measuring the
cross-sectional area and the velocity through the
cross section.
volumetric soil moisture content
The ratio of the
volume of water in a soil to the overall volume of a
soil.
water balance equation
A mathematical descrip-
tion of the hydrological processes operating within
a given timeframe. Normally includes precipitation,
runoff, evaporation and change in storage.
water table
The surface that differentiates between
fully saturated and partially saturated soil/rock.
water vapour
Water in a gaseous form.
well
A tube with permeable sides all the way up so
that water can enter or exit from anywhere up the
column. Wells are commonly used for water extrac-
tion and monitoring the water table in unconfined
aquifers.
wetted perimeter
The total perimeter of a cross
section in a river.
wilting point
The soil water content when plants
start to die back (wilt).
zero plane displacement
The height within a
canopy at which wind speed drops to zero.
