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GEO1020 > Hydrological Processes > Flashcards

Hydrological Processes Flashcards

(60 cards)

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1
Q

What are 3 measurements that can be made in the hydrological cycle?

A

Precipitation
Evaporation
River discharge (river gauging)

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2
Q

What does the lag time show on a hydrograph?

A

The time between rainfall and water entering the stream

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3
Q

What do individual storm hydrographs show?

A

How quickly rainwater moves from the hillslope to the stream channel

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4
Q

How do you find the rise time in a storm hydrograph?

A

Look at the difference between the peak storm flow and the first recorded rainfall

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5
Q

How do you find the lag time on a flood hydrograph?

A

The difference from the midpoint of the rainstorm and the peak storm flow

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6
Q

What is the time scale for studying and monitoring rivers?

A

Hours, days, months

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7
Q

What is the time scale for catchment dynamics?

A

Months, years, decades

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8
Q

What is the time scale for human impacts?

A

Years, decades, centuries, millennia

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9
Q

What is the time scale for natural variability?

A

Centuries onwards

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10
Q

What two things are monitored and studies related to rivers?

A

Environmental quality

Geomorphological processes

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11
Q

What are two key aspects of catchment dynamics?

A

Fluvial and biological responses

Catchment management

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12
Q

What are 5 human impacts?

A 
Acidification
Eutrophication
Desertification
Land-use 
River channel change
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13
Q

What are 3 examples of natural variability?

A

Climate change
Sea level change
Vegetation dynamics

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14
Q

What type of precipitation is easiest to measure?

A

Rain

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15
Q

Why is it difficult to measure snow?

A

Due to under catch

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16
Q

Is the weather radar integrated or instantaneous?

A

Integrated

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17
Q

What is the range of the weather radar?

A

Up to 200km

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18
Q

What is the weather radar range in the UK?

A

15 km

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19
Q

What is the weather radar range in Europe?

A

Over 100 km

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20
Q

What are 7 advantages of weather radars?

A

Area rainfall estimates over a wide area
Information in near-real time
Information for remote land areas and over adjacent seas
Location of frontal and convective (shower) precipitation
Monitoring movement and development of precipitation areas
Short-range forecasts made by extrapolation
Data can be assimilated into numerical weather prediction models

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21
Q

What are 3 disadvantages to weather radars?

A

Display does not show rainfall actually at the surface
Display also shows non-meteorological echoes
Estimates liable to error due to technical and meteorological causes

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22
Q

Explain stochastic variations in precipitation

A

Variability of rainfall in areas of low precipitation as longer records are needed
Timing and magnitude of storms is stochastic

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23
Q

Explain periodic variations of precipitation

A

Regular or cyclic variations
Daily or annual cycles such as convection
Land and sea breezes
Mediterranean winter rain

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24
Q

Explain secular variations of precipitation

A

Climate change

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25
What 5 things does precipitation data show?
``` Mean aerial input of rainfall from a series of point measurements Storm patterns and movement Storm recurrence Probable maximum precipitation Mean rainfall ```
26
What is evaporation a major control on?
The Earth's energy budget
27
How much energy is used to evaporate water as opposed to heat it?
6x more energy is required to evaporate water than to heat if from 0-100 C
28
Where is evaporation highest?
In areas with the highest rainfall
29
Why is evaporation difficult to measure?
There is a loss of water at the surface
30
What needs to be determined to measure evaporation?
The water vapour flux
31
What is used to measure evaporation? (3)
Evaporation pans Water vapour (lysimeter) Weighing block
32
What two things are used to determine discharge?
Channel cross-sectional area | Stream flow velocity
33
What is the discharge equation?
Width x Depth x velocity
34
What is width measured in?
m
35
What is depth measured in?
m
36
What is velocity measured in?
ms-1
37
What are the units for discharge?
m3s-1`
38
What do v-notch weirs allow?
Calculation of discharge using spillway equation
39
What do propellors and impellors measure?
Velocity
40
How often are velocity measurements made?
They are time averaged
41
What are two advantages of measuring velocity with propellors and impellors?
They are robust and easy to use
42
What are two disadvantages of measuring velocity with propellors and impellors?
They disrupt the flow they seek to measure and there are problems of near-bed measuring
43
What is shear stress?
The rate of change of vertical velocity
44
What is Faraday's principle?
A conductor (water) moving through a magnetic field (produced by the sensor) generates a voltage
45
What is voltage measured by in an electromagnetic current meter?
A pair of electrodes
46
What are two advantages of electromagnetic current meters?
Possible to measure flow velocity in different dimensions | Good for use in streams with lots of vegetation and weeds
47
What are ADVs?
Acoustic-Doppler Velocimeters
48
Where can 3D turbulent velocities be found?
In rivers and flumes
49
Where is the transmission of acoustic pulses from in ADVs?
From a transmitter at the probe head
50
What transmission is sent from ADVs?
Acoustic pulses of 10MHz
51
What happens to the acoustic pulse from an ADV?
It is reflected by air bubbles and suspended sediment within the flow
52
How many receivers are in ADVs and what do they surround?
3 receivers surround a sampling volume of water
53
What is the doppler shift from the ADV generated by?
It is generated by velocity differences between probe and scattering objects
54
What is a disadvantage of ADVs?
Cannot measure close to river bed or water surface
55
What are the velocities of ADVs?
Less than 2.5ms-1
56
How does velocity vary?
Vary almost instantaneously and in several directions
57
What are 3 main drawbacks of measuring river discharge?
Cannot gauge rivers all of the time Need to find a simpler way of obtaining river discharge data over longer periods of time Manual or automatic measurement of river level is much easier
58
What relationship is needed?
A stage-discharge relationship
59
What is the stage-discharge relationship derived from?
Multiple river gauging's
60
What conversion is required for stage-discharge relationship?
Conversion of river level (stage) to river discharge values

GEO1020 (16 decks)

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