2. PRECIPITATION
Precipitation in the form of rain, snow, sleet, hail, etc. makes up
the primarily supply of water to the surface. In some very dry
locations, water can be supplied by dew and fog.
3. EVAPOTRANSPIRATION (EVT)
Evaporation is the phase change from a liquid to a gas releasing
water from a wet surface into the air above.
Transpiration is represents a phase change when water is
released into the air by plants.
Evapotranspiration is the combined transfer of water into the air
by evaporation and transpiration.
Actual evapotranspiration is the amount of water delivered to the
air from these two processes. Actual evapotranspiration is an
output of water that is dependent on moisture
availability, temperature and humidity
4. POTENTIAL EVAPOTRANSPIRATION
(P.EVT)
Potential evapotranspiration is the amount of water that would be
evaporated under an optimal set of conditions, among which is an
unlimited supply of water.
The water loss that would occur if there was an unlimited supply
of water.
6. WATER BALANCE
The balance between inputs and outputs of a drainage basin
It is expressed as:
P = Q + E +/- S (changes on storage)
P – Precipitation
Q – Total Streamflow (Discharge)
E – Evapotranspiration
S – Storage (in soil and bedrock)
The difference between actual EVT and P.EVT is in the concept moisture availability.E.g. flower pot.
Here are some questions and answers that will help you to learn to read the graph accurately:In which months is there a water surplus?Jan, Feb, Mar, Apr, Nov, Dec.Why is there soil moisture recharge in October?Due to the excess of evapotranspiration over precipitation in May - Sept.When is field capacity attained?November.Why is a water deficit not shown on the graph?Precipitation always far exceeds evapotranspiration.
