PrecipitationEvapotranspiration
Pond Storage
Overland Flow
Throughfall
Interception
Interception Storage
Infiltration
Soil moisture storage Interflow
Throughflow
Groundwater recharge
Groundwater storage Baseflow
Return flow
Cha
nnel
sto
rage
Run
off
Gro
undw
ater
dis
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Systems science
An approach to hydrological studies in this unit
PrecipitationEvapotranspiration
Pond Storage
Overland Flow
Interception
Interception Storage
Infiltration
Soil moisture storage Interflow
Throughflow
Groundwater recharge
Groundwater storage Baseflow
Return flow
Cha
nnel
sto
rage
Run
off
Gro
undw
ater
dis
char
ge
Koeppen classificationBoM => Climate Services => Climate data online => Climate maps
• Definition: – All forms of moisture being released from the
atmosphere• Snow, hail, sleet, drizzle, rainfall
• Rainfall primary mechanism for Australia/Jordan
Class Definition: according to the UKMO (UK Meteo. office)
Rain Liquid water droplets – 0.5-0.7mm diameter
Drizzle Rain, but with droplets <0.5
Sleet Frozen raindrops (snow and rain)
Snow Ice crystals joined together
Hail Balls of ice – 5-125mm in diameter
Precipitation
Satellite images
PrecipitationBoM => Satellite => Full disk
030
20
1020
10
30
40
Air Temperature oC
Am
ou
nt
of
wate
r vap
ou
r cm
3/m
3
Saturation level
Precipitation
Cloud formation
Convection
Frontal
Orographic
Warm air rises from warm land mass
Warm air rises over cold front
Warm air rises over topographic high
Precipitation
What controls where rain falls?
• Highly variable distribution– At all scales – country to backyard variation
• Altitude, aspect, slope, ocean temperature
Cooler air Weather direction Measurement, angle of rain
About Units...Some hydrologic processes are measured by depth and others by volume.
Rainfall and evaporation are measured by depth (usually millimetres)
One cubic metre (m3) = 1000 litresOne millimetre depth over one hectare = 10m3 10cm depth over one hectare = 1000m3 = 1Megalitre (ML)
Rainfall and evaporation are also by rate (mm/hour, mm/day, mm/year)
Measuring precipitation
Measuring precipitation
Standard rain gauge
Pluviometer
World Meteorological Organisation(WMO)
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
S10
500
1000
1500
2000
2500
3000
An
nu
al R
ain
fall
(mill
imet
res)
Year
Apollo Bay & Weeaproinah 1900 - 2000
TippingBucket
RainGauge
Data loggerconnects tocomputer and www or phone line or telemetry
Automated temporal measurement
Automated recordingof several measurements
Phone or telemetry reading
Optical rain gauge
Measures intensityby rainfall passing
through a light beam
Radar
Temporal distribution- Intensity- Duration
Spatial distribution- Aerial- Virga? or fall?- Fire? Insects?
Evaporation Pan
Pan reading over 24 hours (minus rainfall input)
ET = Pan reading x Pan factor
Pan factor ~ 0.5 to 0.8 usually ~ 0.75
Pan Evaporation conversion to Evapotranspiration
Transpiration
Type and age of plant:• Leaf area• Leaf orientation• Leaf surface• Stomata
Environment: • Humidity• Temperature• Light intensity• Wind• Soil moisture
Measuringeddies
Ventilatedchamber
Sapflow
Porometer
PorometerPortable, widely used in horticultural industry and reasonably easily calibrated
Sap flow measurementUses thermocouple deviceMeasures sap flow in both directionsXylem (flows up)Phloem (flows down)Widely used in forestry industry
Interception, Interception storage, Stem flow, Throughfall
(the hard ones to accurately measure)
Stem flow is measured using interceptor drains around the trunk, Throughfall is measured using rain gauges under the tree canopy
Lysimeters
Direct measurementsWeight changesDeep drainage
ET = Si + PR + IR –Sf - DE
ET = Evapotranspiration in a given time periodSi = Initial soil water volumeSf = Final soil water volumePR = Precipitation into lysimeterIR = Irrigation water into lysimeterDE = Drainage of water from lysimeter
I – O = ΔSHydrologic equation