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333 Exam > 333 > Flashcards

333 Flashcards

1
Q

Inconsistency in Rainfall Data and how to fix it (4)

A

Site:

  1. condition of gauge
  2. condition of surrounding area

Data:

  1. check for obvious errors/patterns (time series plot)
  2. test consistency using Double Mass Curve.
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2
Q

Isohytel Method (2)

A
  • Isohyets are contour lines of equal rainfall depths

- The mean areal rainfall is the weighted average of the rainfall depths between any two successive isohyets

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3
Q

Thiessen Polygon Method (2)

A
  • catchment divided into polygons, one for each gauge station
  • The polygon around each station contains that portion of the catchment which is nearer to that station than to any other
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4
Q

Hypsometric Method (4)

A
  • takes into consideration of orthogonal effects
  • plot elevation vs rainfall
  • plot elevation vs area above specific rainfall
  • divide the curve above into a number of different elevation zones and calculate using R=SUM(Ri*ai)
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5
Q

Arithmetic Method (1)

A
  • an average of each rainfall depth at each gauge site.
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6
Q

Effects of time interval of variability (1)

A
  • The variability increases as the time interval increases
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7
Q

Impact of climate change on frequency analysis (1)

A

changes in water level etc may cause non stationarity in the data of the time series plot.

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8
Q

Assumptions of frequency analysis (3)

A
  1. The series is a random sample from a population
  2. The population parameters can be estimated from the sample
  3. Stationarity of the X-T relationship
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9
Q

basis of construction probability paper (5)

A
  1. distorts the ordinate axis to obtain a linear relationship
  2. involves ranking the data according to magnitude
  3. the ranked data is plotted
  4. a line of best fit can be drawn
  5. slope and intercept parameters can then be used to get the parameters of the distribution
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10
Q

problems with the least squares method (2)

A
  • easily influenced by outliers

- best for use of 2 parameter distributions

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11
Q

problems with unit hydrograph method (3)

A
  • separation of base flow
  • estimation of effective rainfall
  • very subjective process
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12
Q

assumptions in Curve Number Method (3)

A
  • assumes that runoff begins after some initial abstraction
  • viewed as an infiltration loss model
  • ratio between actual and potential quantities are equal
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13
Q

factors which affect soil infiltration (6)

A
  • slope (larger slope, larger infiltration)
  • soil type (coarse have larger infiltration than fine)
  • land cover
  • temp (frozen soils become too dense)
  • initial moisture content (high initial moisture content means lower infiltration)
  • depth of groundwater table (short depth, less infiltration)
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14
Q

calibration/verification of field data or V notch etc (6)

A
  • collect synchronised discharge and stage measurements
  • discharge can be measured using a variety of methods (velocity area, dilution gauging)
  • stage can be measured using a staff gauge
  • data collected should show a similar range of the table
  • compare measured and theoretical data
  • adjust parameters of the theoretical curve as required
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15
Q

factors to be included with a rainfall gauge installation (5)

A
  • vandalism
  • accessibility
  • power supply (solar)
  • redundancy (automatic or manual)
  • surrounding (trees)
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16
Q

factors to be included with a river flow gauging (6)

A
  • vandalism
  • accessibility
  • risk of failure during extreme events
  • stability of river cross section (erosion)
  • maintenance
  • power supply
17
Q

basis of satellites (1)

A
  • the duration spent by an area having cloud top temps below 40 degs is the Cold Cloud Duration which can be used to calculate rainfall
18
Q

basis of radar (3)

A
  • radars emit electromagnetic energy and some can be reflected when it hits clouds
  • the reflected energy returns to the transmitter
  • this can be used to calculate rainfall
19
Q

benefits of radars over rainfall gauges (1)

A
  • better spatial and temporal resolution of rainfall
20
Q

basis of velocity area method (3)

A
  • divide the section into subsections
  • measure velocity at one or more depths
  • calculate discharge using numerical integration
21
Q

basis or ordinary moments (4)

A
  • Derive theoretical relationships between the moments and the parameters of the distribution
  • Calculate sample estimates
  • Equate sample estimates to the theoretical expressions
  • Solve the resulting equations
22
Q

basic principles of unit hydrograph (3)

A

superposition: A number of effective rainfall blocks equal to the sum of the runoff hydrographs produced by each block.
proportionality: Different rainfall intensities, but of equal duration are in the same proportion to each other.

time invariance: The effective rainfall vs storm runoff relationship does not change with time

23
Q

impacts of urbanisation on the hydrological cycle (3)

A
  • Increase in surface runoff
  • Decrease in evapotranspiration
  • Decrease in infiltration, groundwater recharge and baseflow
24
Q

role of hydrology on storm water with water sensitive design (2)

A
  • This approach uses distributed, de-centralized, small-scale on-site devices used to mimic pre-development hydrology of the site.
  • Conservation requires delineation of hydrologically sensitive areas
25
Q

advantages of indigenous knowledge (3)

A
  • Co-produced knowledge
  • Improve decision making
  • Advance modern science
26
Q

water year definition (2)

A
  • 12 month period when the stream flow is minimum

- encompasses the wet season without dividing it

27
Q

unit hydrogrpah theory (4)

A

baseflow: lower portion of the discharge hydrograph, which varies slowly through the year.

unit volume: 1 cm of excess rainfall over the catchment area

excess rainfall: the remaining rainfall after allowing for rainfall losses

duration of unit hydrograph: duration of effective rainfall

333 Exam (1 decks)

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