Hydrological cycle and observation Flashcards
Water movement - one location to another
- precipitation: rainfall/snow
-ground
-soil(by infiltration)
-runoff(river flow)
-ocean
Water movement- phase change
-condensing(vapour to rain droplets)
-melting(snow to rain)
-evaporating(water to vapour)
-sublimation(vapour to ice crystal/clouds)
Water movement- energy exchange
Latent heat change
What affects water - distribution
-dependant on climate zones
-huge variability I’m both space and time
-climate change
Water quality
-interfered with human activities
-water supply and sanitation
Main input precipitation
-evapotranspiration
-ground water recharge
-(environmental) outflow
River catchment
The drain area of surface water affected by the local topography and geology
Hydrological budget
I - O = ds/dt
Where…
I : precipitation, inflow at the boundary
O : outflow at the boundary(evaporation, transpiration)
S: groundwater, aquifer
Units in calcs
Volume = flow rate x time
Depth = volume / area
USE MM - easier to compare
Humidity
Measurement of water vapour in the air
Absolute humidity
The mass of the water vapour per unit volume of the moist air in kg/m3
Specific humidity
The mass ratio between the water vapour and the moist air, in g/kg
Water vapour pressure
Partial pressure due to the existence and the movement of water vapour molecules ( e represents )
Saturation water vapour pressure (es)
An equilibrium state meaning that it can contain no more water vapour molecules
Air can contain more water vapour as temp. increases
Relative humidity (%)
Ratio between absolute humidity and specific humidity
- h = e/es
-takes into account effect of temp.
Dew point temperature (td)
The temperature at which the water vapour begins to condense (dew will form at certain surfaces)
-by comparing the current temperature and the dew point, we can have an idea of how humid the air is
Wet-bulb temperature (tw)
The resultant temperature when vapour saturation is reached by evaporating water into the air (therefore cooled down)
Psychometric chart
Shows relationship between saturated water vapour pressure and temperature
Bowen ratio
A ratio of the latent heat and sensible heat during phase change
Measurement - temperature
-recorded by thermometers in open boxes (1.25m above ground)
-distribution of temp. is influenced by latitude, altitude, topography and vegetation
Measurement - radiation
Incoming and net radiation measured using radiometers
Measurement - wind
-speed and direction measured by anemometer and wind vane
-specify height at which measurement is taken…
u/u0 = (z/z0)^0.15
where…
-u/u0 is wind speeds at height z0
-higher level z
