GLOSSARY - Fundamentals of Hydrology - page 180

quickflow See stormflow .
rainfall Precipitation in a liquid form. The usual
expression of rainfall is as a vertical depth of water
(e.g. mm or inches).
rainfall intensity The rate at which rainfall occurs.
A depth of rainfall per unit time, most commonly
mm per hour.
rain gauge An instrument for measuring the
amount of rainfall at a point for a period of time.
Standard rain gauges are measured over a day;
continuous rainfall measurement can be provided
by special rain gauges such as the tipping-bucket
gauge.
rain shadow effect An uneven distribution of
rainfall caused by a large high landmass (e.g.
a mountain range). On the downwind side of the
mountain range there is often less rainfall (i.e. the
mountain casts a rain shadow).
rating curve The relationship between river stage
(height) and discharge.
recession limb (of hydrograph) The period after
a peak of stormflow where the streamflow values
gradually recede.
relative humidity How close to fully saturated the
atmosphere is (a percentage - 100 per cent is fully
saturated for the current temperature).
rising limb (of hydrograph) The start of a storm-
flow peak.
river A large natural stream of water flowing over
the surface and normally contained within a river
channel.
river basin The area of land from which water
flows towards a river and then in that river to the
sea. Also known as the river catchment.
roughness coefficient A term used in equations
such as Chezy and Manning's to estimate the degree
that water is slowed down by friction along the bed
surface.
runoff The movement of liquid water above and

below the surface of the earth prior to reaching a
stream or river.
salination The build up of salts in a soil or water
body.
satellite remote sensing The interpretation of
ground (or atmospheric) characteristics based on
measurements of radiation from the earth/atmos-
phere. The radiation measurements are received on
satellite-based sensors.
saturated overland flow Overland flow that
occurs when a soil is completely saturated.
saturated water content The maximum amount
of water that the soil can hold. It is equivalent to
the soil porosity, which assumes that the water fills
all the pore space within a soil.
saturation vapour pressure The maximum
vapour pressure possible (i.e. the vapour pressure
exerted when a parcel of air is fully saturated). The
saturation point of an air parcel is temperature-
dependent and hence so is the saturation vapour
pressure.
sensible heat The heat which can be sensed or felt.
This is most easily understood as the heat we feel as
warmth. The sensible heat flux is the rate of flow of
that sensible heat.
snowfall Precipitation in a solid form. For hydrol-
ogy it is common to express the snowfall as a vertical
depth of liquid (i.e. melted) water.
snow pillow An instrument used to measure the
depth of snow accumulating above a certain point.
soil heat flux Heat released from the soil having
been previously stored within the soil.
soil moisture characteristic curve A measured
curve describing the relationship between the
capillary forces and soil moisture content. This is
also called the suction moisture curve.
soil moisture deficit The amount of water
required to fill the soil up to field capacity.
soil moisture tension See soil suction .