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HYDROLOGY > CHAPTER 2 > Flashcards

CHAPTER 2 Flashcards

1
Q

That part of atmospheric moisture that falls on the earth surface

A

PRECIPITATION

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2
Q

what are the 10 types of precipitation?

A
  1. rain
  2. ice crystals
  3. sleet
  4. freezing rain
  5. snow
  6. snow grains
  7. graupel
  8. hail
  9. drizzle
  10. freezing fog
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3
Q

Water droplets in clouds are formed by nucleation of vapor on aerosols, then go through many condensation evaporation cycles as they circulate in the cloud, until they aggregate into large enough drops to fall through the cloud base.

A

SUBLIMATION NUCLEI

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4
Q

a process of artificially nucleating clouds to induce precipitation

A

CLOUD SEEDING

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5
Q

is a common nucleating agent and is spread from aircraft in which a silver iodide solution is evaporated with a propane flame to produce particles.

A

SILVER IODINE

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6
Q

___________ and ___________are known to co-exist in the atmosphere at sub-freezing temperatures.

A

ICE CRYSTALS and WATER DROPLETS

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7
Q

_________ of water droplets as a result of their coming in contact through the action on them of air movement and
gravitational pull.

A

COALESENCE

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8
Q

air is drawn upwards by convective action, such as in the center of a thunderstorm cell

A

CONVECTIVE PRECIPITATION

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8
Q

where warm air is lifted over cooler air by frontal passage

A

FRONTAL PRECIPITATION

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9
Q

which an air mass rises to pass over a mountain range

A

OROGRAPHIC PRECIPITATION

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10
Q

what are the 4 types of precipitation?

A
  1. CONVECTIVE PRECIPITATION
  2. FRONTAL PRECIPITATION
  3. OROGRAPHIC PRECIPTATION
  4. CYCLONIC PRECIPITATION
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11
Q

the simplest method of determining areal average rainfall which involves averaging the rainfall depths recorded at a number of gages

A

ARITHMETIC AVERAGE

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12
Q

This method is satisfactory if the gages are uniformly distributed over the area and the individual gage measurements do not vary greatly about the mean.

A

ARITHMETIC AVERAGE

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13
Q

Assumes that at any point in the watershed the rainfall is the same as that at the nearest gage so the depth recorded at a given gage is applied
out to a distance halfway to the next station in any direction.

A

THIESSEN METHOD

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14
Q

The relative weights for each gage are determined from the corresponding areas of application in a Thiessen polygon network, the boundaries of the polygons being formed by the ____________.

A

PERPENDICULAR BISECTORS OF THE LINES JOINING ADJACENT GAGES.

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15
Q
  • Composed of isohyets which are lines of
    equal rainfall magnitude
  • Most accurate and more flexible than
    Thiessen method
  • Harder to construct for complex storms
    with dense network of gages
A

ISOHYETAL METHOD

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16
Q

The gaging networks in the Philippines

A
  • Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) weather stations and facilities (more or less 500 in total)
  • PAGASA Automated Weather Stations (AWS)
  • National Irrigation Administration
  • Bureau of Forest Development and the
  • Bureau of Plant Industry
  • State colleges and Universities
  • Private entities
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17
Q

3 types of estimation of Areal Precipitation

A

a. ARITHMETIC AVERAGE
b. THIESSAN METHOD
c. ISOHYETAL METHOD

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18
Q

2 types of rainfall adjustments

A

A. Estimation of Missing Rainfall Data
B. Adjustment of Rainfall due to Changes in Locations

19
Q

Complete measured precipitation data are important to many problems in hydrologic analysis and design but there are missing values

A

ESTIMATION OF MISSING RAINFALL DATA

20
Q

type of Estimation of Missing Rainfall Data that is preferrable for relatively flat areas

A

STATION-AVERAGE METHOD

21
Q
  • A consistent record is one where the characteristics of the record have not changed with time
  • An inconsistent record may result from any one of a number of events
A

ADJUSTMENT OF RAINFALL DUE TO CHANGES IN LOCATION

22
Q

is the method that is used to check for an
inconsistency in a gaged record.

A

DOUBLE-MASS CURVE ANALYSIS

23
Q

is a graph of the cumulative catch at the rain gage of interest versus the cumulative catch of one or more gages in the regions that have been subjected to similar hydrometeorological occurrences and are known to be consistent

A

DOUBLE-MASS CURVE

24
Q

If a double- mass curve has a constant slope, the record is ________.

A

CONSISTENT

25
Q

If a double –mass curve has not a constant slope, the record is ________________.

A

NOT CONSISTENT AND NEED TO BE ADJUSTED

26
Q

what are the 4 characteristics of a rainstorm?

A
  1. Intensity (mm/hr)
  2. Duration (min, hours, days)
  3. Areal extent (m2, ha): area over which it is distributed
  4. Frequency: once in 5, 10, 15, 20, 25, 50 or 100 years
26
Q
  • graph showing the depth or intensity of
    rainfall with respect to time
  • useful in determining the maximum
    intensities of rainfall during a particular
    storm as is required in land drainage and
    design of culverts.
A

HYETOGRAPH

27
Q

3 basic terms in Statistical Hydrology

A
  • Time period of interest (N)
  • Probability of occurrence (P)
  • Recurrence interval or return period (T)
28
Q

probability that a T-year storm may occur
in any series of N years.

A

PROBABILITY OF EXCEEDANCE

29
Q
  • Enables the hydrologists to develop hydrologic systems that consider worst-case scenarios of rainfall intensity and duration during a given interval of time
  • It is often used by entering with the duration and frequency to find
    the intensity. Or
  • It is used to find the frequency for a measured storm event. The
    predicted frequency is determined by finding the intersection of the
    lines defined by the measured intensity and the storm duration.
A

IDF CURVE (Intensity vs. Duration vs. Frequency)

30
Q

Refers to the probabilistic analysis of hydrologic processes.

A

HYDROLOGIC FREQUENCY ANALYSIS

30
Q

probability that a T-year storm may
NOT occur in any series of N years

A

PROBBAILITY OF NON-EXCEEDANCE

31
Q

any hydrologic phenomenon which undergoes continuous changes with time.

A

HYDROLOGIC PROCESS

32
Q

Categories of Hydrologic Process

A
  1. DETERMINISTIC
  2. PROBABILISTIC
  3. STOCHASTIC
33
Q
  • is one in which a definite law of certainty exists
  • it is one where the chance element is ignored as in the case of flood routing
  • Commonly used for man-made canals channels
A

DETERMINISTIC PROCESS

34
Q
  • is one governed by chance
    phenomena, that is, there are
    so many causes at work that
    the influence of one cannot be
    readily identified
  • Time-series independent
A

PROBABILISTIC PROCESS

35
Q
  • means that the sequence of occurrence of events or the time series is considered in its analysis
  • Time-series dependent
A

STOCHASTIC PROCESS

36
Q

what is the objective of Hydrologic Frequency Analysis?

A

to relate the magnitude of events to their frequency of occurrence through probability distribution, that is, a frequency curve

37
Q

steps in Frequency Analysis

A
  1. Selection of Data
  2. Determination of Statistical Parameters
  3. Fitting of Data
  4. Testing the Significance of Results
38
Q

types of Probability Density Function

A
  1. Normal density function
  2. Log-normal function with two parameters
  3. Gamma density function with two parameters
  4. Kappa density functions with two parameters
38
Q

all data above a given threshold value

A

PARTIAL DURATION SERIES

38
Q

only one data point per year, usually the maximum

A

ANNUAL SERIES

39
Q

a hydrologic event is not influenced by another event

A

INDEPENDENCE

39
Q

events under the same type of conditions or statistical properties are not changing

A

HOMOGENITY

40
Q

Fitting of data to known statistical distributions

A
  • Normal distribution
  • Log-normal distribution
  • Log-Pearson Type III distribution
  • other applicable density functions

HYDROLOGY (2 decks)

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