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Hydrology > Week 1 > Flashcards

Week 1 Flashcards

1
Q

Components of hydrological cycle

A

Rain/snow

Glaciers

Volcanos and juvenile H2O

Infiltration

Saturated zone

Groundwater flow

Water table

Runoff

Overland flow

Evapotranspiration

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2
Q

P > VP =

A

PPT

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3
Q

P < VP =

A

EVAP

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4
Q

VP at high altitude

A

Low T
Low VP
= PPT

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5
Q

VP at low altitude

A

Higher VP (column of air above) e.g. SL ~100kPa
Higher T
= EVAP

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6
Q

Direct rainfall measurement

A

NON RECORDING RAIN GAUGE
- manually records mm/day

TIPPING BUCKET RAIN GAUGE
- continuous time b/w 0.2mm of rainfall

TILTING SYPHON RAIN GAUGE

  • continuous water level w/ float gauge
  • once can full = trigger = empties
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7
Q

Radar measurement

A

Good for spatial coverage

Electromagnetic energy pulse reflected by pption particles
Echo intensity = raindrop size

e.g. 15 radars in UK
5 in Ireland

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8
Q

Surface dominated catchment

A

Discharge reacts quickly to rainfall events - surface flow

Summer = low flow

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9
Q

Groundwater dominated catchment

A

Discharge less responsive

Substantial summer flows

Most flow from groundwater = springs/upwelling in river channels

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10
Q

Catchment water balance eqn

A

Discharge = rainfall - evapotranspiration - /\storage

N.B. /\ storage changes due to permeability

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11
Q

Velocity meters

A

Series of discrete points

Measures flow velocity and depth of water

Ideally 60% depth

–> Q

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12
Q

Stage =

A

River level above defined datum

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13
Q

Stage gauging

A

Auto-measurement = efficient and continuous flow measurement

Uses weir

STAGE(y)-DISCHARGE(x) RELATIONSHIP REQUIRED

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14
Q

What does Manning’s equation do?

A

Relates water level and flow rate

Empirical equation

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15
Q

Evaporation =

A

Loss of water from open surface

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16
Q

Evapotranspiration =

A

Loss of water from open surface and also wet canopy evaporation and transpiration

17
Q

Potential evaporation =

A

Amount of water that would evaporate and transpire given an unlimited water source

18
Q

Actual evaporation =

A

Actual amount of water that evaporates and transpires

19
Q

Forest rainfall partitioning equation

A

Rainfall = stem flow + through flow + interception loss

20
Q

Pan =

A

Open water surface

21
Q

Pan evaporation =

A

Direct water loss measurement from open water surface over time

22
Q

Pan evaporation eqn

A

PE = kp x Epan

kp = lumped correction factor; accounts for differences between pan/crop e.g.

  • radiation balance due to albedo
  • energy balance (lots of energy in water)

Design (colour/shape/sunken into ground etc) affects performance!!!

23
Q

Factors affecting evaporation (explained)

A

SUNLIGHT
- energy required for latent heat

TEMP
- high T = water evaporated more readily AND air can hold more water

HUMIDITY
- air = vapour saturated = evaporation not possible

WIND

  • multi scale Eddy patterns
  • rate of dry air replenishment

SOIL WATER
- = evapotranspiration

PLANT TYPE

  • transpire different rates
  • interception
24
Q

Automatic weather station

A

Takes all factors affecting evaporation into account:

Solar panel

Relative humidity/T sensor with radiation shield

Wind direction/speed

Solar radiation panel

Power supply and data logger

25
Q

Energy balance equation

A

Rn = L + H + G

Rn = net radiation, mostly from solar

L = latent heat flux, req to vaporise water loss due to evaporation

H = sensible heat, heat you feel

G = soil heat flux; net loss into ground (small daily changes b/c +day and -night)

26
Q

Measurement of actual evaporation (eddy)

A

Eddy flux measurement

Concept: air flow = horizontal flow of numerous eddies
Evapotranspiration = net upwards moisture flow

E = vertical wind velocity (sonic anemometers) x water vapour conc, humidity (IR gas analysers)

27
Q

Sonic anemometer =

A

Uses flight time of ultrasonic pulses b/w pair of transducers

28
Q

Penman Combination equation

A

PE = eqn

Takes into account energy used to convert water liquid to gas AND wind to remove humid packets of air away from the surface (i.e. the drying power of air)

29
Q

Measurement of actual evaporation (lysimeter)

A

Isolate a volume of soil = absolute outflow control

  • rainfall measured
  • drainage collected
  • storage determined (weigh)

Aim to reproduce natural conditions w/ vegetation/siting/soil structure

Evaporation estimated by water balance method

30
Q

Empiral relationships with T

A

BLANEY-CRIDDLE
- PE = (Psun/100)(0.46T+8.13)

THORNTHWAITE-CROWE
- PE = 0.165T+2.01

Both only suitable on monthly basis
T-C only suitable for summer b/c low daylight hours in winter

31
Q

Mannings coefficient; canals/rivers in good condition

A

0.025

32
Q

Mannings coefficient; canals/rivers in bad conditions

A

0.035

33
Q

Mannings coefficient, smooth cement, planed timber

A

0.010

Hydrology (9 decks)

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