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HYDROLOGY > LESSON 6 > Flashcards

LESSON 6 Flashcards

1
Q

process and pathways through which excess water becomes streamflow’; excess water is that part of the total rainfall amount which runs off the land surface, and that which drains from the soil and is not consumed in evapotranspiration

A

Runoff

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2
Q

pathway in which rain falls directly into the stream channel

A

Channel Interception

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3
Q

pathway in which excess water flows
over the soil surface

A

Surface Runoff or Overland Water Flow

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4
Q

pathway in which excess water infiltratesinto the soil but then arrives at a stream channel in a short amount period of time

A

Subsurface Flow or Interflow

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5
Q

sum of channel interception, surface flow and subsurface flow

A

Direct Runoff or Stormflow

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6
Q

a tabular or graphical representation of streamflow discharge vs time

A

Streamflow Hydrograph

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7
Q

Precipitation must satisfy the demands of
evaporation, interception, infiltration,
surface storage, surface detention, and
channel detention before runoff can occur.

A

Runoff Process

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8
Q

Runoff process

A
  1. Rainfall Intensity > Infiltration Rate
  2. Water begins to fill depression on soil surface
  3. Overland flow begins as depressions are filled
  4. Build up water on the surface (surface detention) = P - infiltration - interception
  5. Flow moving into defined channels (Channel Detention)
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9
Q

Factors affecting runoff

A
  1. Rainfall
  2. Watershed
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10
Q

Effects of Rainfall to runoff

A

duration, intensity and areal distribution

  1. Duration influences total runoff
  2. Intensity influences rate and volume of runoff
  3. Intense storms decreases infiltration rate because of its destructive effect on soil surface
  4. Areal distribution of rainfall influences rate of infiltration and volume runoff
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11
Q

Effects of watershed to runoff

A

size, shape, orientation, topography, geology and surface culture

  1. As watershed size increases, the volume and rate of runoff increases
  2. As the runoff area increases, the volume and rate of runoff decreases
  3. Long and Narrow watersheds have low runoff rate
  4. Runoff is decreases for storms moving upstreams
  5. Flat areas have low runoff
  6. Geology, soil materials and vegetation affect infiltration rate, also runoff
  7. Structures such as dams affects runoff rate
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12
Q

Measurements of Streamflow

A
  1. Stage
  2. Rating curve
  3. Control Section
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13
Q

Height of water in a stream

A

Stage

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14
Q

Graph of stage and streamwater discharge

A

Rating Curve

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15
Q

Section of the stream where rating curve will be deployed

A

Control Section

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16
Q

Requirements for deploying Control Section

A
  1. Stream should be stable and have sufficient depth for velocity measurement
  2. should have a straight upstream distance of 5x width of the stream and downstream distance of 2x width of the stream
  3. Free of obstruction (Vegetation, boulders etc.)
17
Q

Measurement of Stage

A

Staff Gauge
Continuous water level recorder

18
Q

A graduated staff used for visual observation of water level

A

Staff Gauge

19
Q

Measurement of Velocity

A

Float Method
Current Meter Method

20
Q

the time required for a floating object that is tossed into the stream to travel a specified distance on the surface of the water is observed. Then surface velocity is determined by dividing distance/time. Average velocity is 80-85% of Surface velocity

A

Float Method

21
Q

For Floating method, what is the formula for streamflow discharge?

A

the average velocity is multiplied by cross-sectional area of the stream to estimate streamflow discharge

Q = VA

22
Q

An instrument in which a wheel is made to rotate about its axis by the force of current. The speed of rotation determines the velocity of water.

A

Current meter method

23
Q

Formula for Water velocity for current meter method

A

V = a+bN

V = average velocity
a,b = constants
N = revolutions per unit time

24
Q

Stream depth > 0.5m measurements are taken from where?

Stream depth < 0.5m, measurements are taken from where?

A
  1. 20% and 80% of the total depth then get the average
  2. 60% of the toal depth
25
Q

Streamflow discharge formula for Current meter method

A

Q = Z(AiVi)

Z = Summation
Ai = Average area per section
Vi = Average velocity per section

26
Q

barriers placed across the stream over which water flows; provides a simple and accurate means of measuring water

A

Weirs

27
Q

height of water above the crest

A

Head

28
Q

edge or surface over which the water flows

A

crest

29
Q

Type of Crest

A

Rectangular, Trapezoidal (Cipolletti), or Triangular (V -notch)

Sharp-crested

Broad-crested

30
Q

has a blade with a sharp upstream edge, so that the passing water touches only a thin edge and clear the rest of the crest

A

Sharp-crested

31
Q

has a flat or broad surface over
which the water flows

A

Broad-crested

32
Q

artificial open channels built to contain streamflows within designed cross-sectional areas and length

A

Flumes

33
Q

Types of flumes

A

Parshall Flume
Trapezoidal Flume

HYDROLOGY (7 decks)

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