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Hydro. Exam 1 Concepts > EX1 > Flashcards

EX1 Flashcards

1
Q

How to Manually Delineate a Watershed

A
  1. Get map-Overlay the map
  2. Locate outlet on map
  3. Identify existing drainage network
    4.Identify high ground
    5.Starting at the outlet, visualize flow paths
  4. Perform water drop test
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2
Q

Delta Storage Equation

A

deltaS=P-(G+F+E+R+T)

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3
Q

1 Acre Conversion

A

43560 ft^2

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4
Q

Types of Rainfall

A

Cyclonic
Orographic
Convective

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5
Q

Cyclonic

A

Long storm durations
Cold or warm fronts
Cold fronts often form tornadoes

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6
Q

Orographic

A

Intense storms
westerly sloped mountains
Common in Denver, SW monsoonal moisture

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7
Q

Convective

A

Heavy thunderstorms
heavy rain from slow moving storms

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8
Q

Rainfall Measurement

A

Physical measurement on ground (Gages)
Radar Rainfall
Gauge Adjusted Rainfall (GARR)

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9
Q

Tipping Bucket Rain Gauge

A

Measures time and depth

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10
Q

Approaches to interpolate rainfall

A

Areal Average
Thiessen Polygon
Isohyetal
Doppler Radar

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11
Q

Arithmetic Mean

A

gauges in watershed
simple
least accurate
ok with uniformly spread gages
p=1/n summation Pi

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12
Q

Thiessen Polygon

A

Gages in or near watershed
a weight technique
most widely used

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13
Q

Isohyetal

A

contours of consistent precipitation
need extensive gage network

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14
Q

Doppler Radar

A

Most accurate

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15
Q

Thiessen Polygon Method

A
  1. Connect each rain gage use dashed lines
  2. Create a bisect line to each dashed line
  3. Extent bisect lines to the watershed
  4. Connect bisect lines

p=1/A summation Ai*Pi
A=summation Ai

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16
Q

Importance of Streamflow

A

Municipal water supply
Water rights allocation
Reservoir operations

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17
Q

John Wesley Powell

A

Expedition to survey the west
Professor in Illinois
Went down Grand Canyon/Lake Powell
Flow measurement

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18
Q

Streamflow

A

Discharge, Q
Rate at which volume of water passes through cross section of area
Q=VA

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19
Q

Streamflow Devices/Methods

A

Gaging rod
Dye tracer test
Float method
ADCP (Acoustic Doppler Current Profiler)

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20
Q

USGS Method

A

Subsection widths
Q=summation Vidiwi

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21
Q

Stream gage technologies

A

Stilling Well
Pressure transducer

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22
Q

Rating Curve

A

Represents sate vs discharge ( gage H vs Q)
Convert water level readings into flow rate
Create it
Use it
Adjust

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23
Q

Evaporation

A

water transformed to vapor from liquid

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24
Q

Evaporation affected by

A

soil type, soil moisture content, temp …..

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25
Q

Transpiration

A

Water moves through plants and evaporates through leaves

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26
Q

Transpiration affected by

A

Type of vegetation, Growth stage

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27
Q

Pan evaporation

A

pan designed to measure evaporation by monitoring loss of water over time

28
Q

Why probability and frequency analysis?

A
  1. Hydrologic processes are random
  2. Use stats to interpret and predict
29
Q

Random variables

A

Discrete
Continuous

30
Q

Discrete RV

A

A countable # of distinct values
# of children in family
# of students in classroom

31
Q

Continuous RV

A

An infinite # of possible values
height, weight …..

32
Q

Return Period

A

The average time between events
p=1/T

33
Q

Reliability

A

The probability that a T-year storm event will not occure in n years
R=(1-P)^n

34
Q

Risk

A

Probability that a T-year storm will occur at least once in n years
Risk=1-R

35
Q

Binomial Distribution

A

Probability of n successes in N trails independent from each other

36
Q

Infiltration

A

Water that goes into the ground

37
Q

Interception

A

Water that does not hit the ground
(hits trees)

38
Q

Infiltration Capacity

A

Max infiltration rate

39
Q

Green-Ampt Model

A

Best for soil that exhibit a sharp wetting front
Darcy’s Law (Ifiltarion is proportional to gradient)

40
Q

Horton’s Method

A

Used to describe potential infiltration rate vs time
Decay graph

41
Q

Phi index method

A
  1. Calc volume of direct runoff
  2. Assume # of intervals
  3. Sum of rainfall in each interval
  4. Calc phi
  5. check phi vs excess precipitation
  6. Iterate if necessary
  7. Check Pe=rd
42
Q

Model Phi Index

A

An index only
Intensity can be taken uniformly
Non-linearly depending on index

43
Q

Model Hortons

A

Empirical
Nonlinear
Represented by a first order math equation

44
Q

Model Green-Ampt

A

Analytical basis on soil properties
Nonlinear
Wetting front travels through soil
Account for unsteady rainfall

45
Q

Hydrologic Design

A

Assessing impact of hyrdologic events
Determining values for key variables
Design system to perform adequately

46
Q

Hydrologic Design process

A
  1. Select runoff
  2. Predict runoff
  3. Route flow
  4. Evaluate flow at points of interest
  5. Design system
  6. Iterate

r

47
Q

Estimated limiting value

A

largest possible for a hydrologic event at given location (based on the best hydro info)

48
Q

Probable Max Precipitation (PMP)

A

estimated greatest depth of precipitation for a given duration that is physically possible and depth of rain

49
Q

Probable max storm (PMS)

A

rain over time

50
Q

Probable max flood (PMF)

A

Greatest possible flood assuming complete coincidence of all factors that would produce the heaviest rainfall and max runoff

51
Q

Intensity-Duration-Frequency (IDF)

A

Curves representing a localized relationship amoung intensity and duration

52
Q

Standard Project Storm (SPS)

A

Greatest storm that may be reasonably expected

53
Q

Standard project flood

A

design flood, estimated using rainfall-runoff modeling

54
Q

TP-40

A

Rainfall frequency, depth of rainfall

55
Q

NOAA

A

Rainfall frequency, yields depth of rainfall

56
Q

Rational Method

A

Q=kCiA

57
Q

Time of concentration

A

time for an entire water shed to contribute to runoff

58
Q

Sheetflow

A

Less shallow, cannot exceed 300ft

59
Q

Shallow

A

shallow, can exceed 300 ft

60
Q

Rational method steps

A

1.find c and n values
2.Areas of each land type
3.tc for each flowpath
P2 from TP-40
V from TR-55
tc from TR-55 ws
4. choose longest time
5. IDF to find i
6. plug into Q=kCiA

61
Q

Factors affecting hydrographs

A

Intensity
rainfall duration
watershed size
etc

62
Q

Characteristics on flood hyrdrograph

A

slope
roughness
storage
drainage intensity
channel length
above all to runoff

63
Q

UHG

A

Unit Hyrdrograph
depth of 1 in or 1 cm of Pe

64
Q

DRH

A

Direct Runoff hydrograph

65
Q

CN

A

Curve Number
land use
soil type
antecedent runoff conditions

66
Q

ARC

A

arc 2 = normal
arc 1= dry
arc 3 =wet

Hydro. Exam 1 Concepts (1 decks)

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