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Hydrology > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What is hydrology?

A

Study of water, distribution of all water, movement of all water.

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2
Q

What is the source of all water on the planet?

A

Comets are the source of all water on the earth.

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3
Q

Discuss distribution of water?

A

Water is not evenly distributed nor evenly accessible. Hydrologist try to resolve those issues.

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4
Q

How does water effect climate?

A

It acts as a ameliorator and dictates climate. Energy is bored and released during phase changes. Water is really good at holding temperature and emitting it back. Warm helps define how warm the planet is.

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5
Q

Physical and chemical properties of water

A

Dihydrogen monoxide. Covalent bond-shared electron and extremely strong. The most corrosive substance on earth.

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6
Q

Why are the hydrogen bonds in water important?

A

Hydrogen bonds allow water to move freely, they break easily and allows water to reshape or form such as freezing or evaporating. Universal solvent, low viscosity allows it to move quickly.

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7
Q

Describe solid ice

A

Rigid crystalline structure, lower density as solid than liquid (rare). Frozen water floats, allows things to live in deep water. Freezes from the top down, because less dense when frozen and life can form underneath the ice.

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8
Q

When does the density of water change?

A

The maximum density of water is 3.98C. Thermal stratification.

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9
Q

Specific heat capacity of water

A

4.2 kJ/kg/K which is much higher meaning it absorbs heat really well. Specific heat is the energy required to raise something 1C. Heat causes movement. Takes more energy to increase by 1C.

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10
Q

Water movement

A

Water movement accounts for 70% of global latent heat transfer.

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11
Q

Greenhouse gas?

A

Water vapor is greenhouse gas. Short-wave radiation heats. Long-wave emits back, but trapped by gas. Water vapor is the biggest green house gas. Energy is either bounced back out of the atmosphere or reflected back down to the earth.

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12
Q

How much water is located in the oceans?

A

96.54%

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13
Q

Discuss the different parts of the global hydrologic scale?

A

Evaporation (E), precipitation (P), subsurface runoff (Qg), and surface runoff (Q).. 1.36–>1.45 billion cubic km of water

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14
Q

What is evaporation?

A

(E) liquid water to water vapor (i.e., steam)

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15
Q

What is precipitation?

A

water vapor to liquid water, rain

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16
Q

What is runoff?

A

water moving over land surface, streams rivers, runoff.

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17
Q

What is a catchment?

A

The area land to which water drains. All water drains to a single point. Separated by ridges. Catchment basin, watershed, drainage. HUC’s

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18
Q

Components of catchment cycle

A

Evaporation, precipitation, runoof

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19
Q

What is the water balance equation?

A

Input-output=change in storage. I-O=S

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20
Q

What are inputs to the water balance equation?

A

I=precipitation (P) + Groundwater input (Gin)

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21
Q

What are outputs from the water balance equation?

A

Evapotranspiration (ET) + Streamflow (Q) + Groundwater input (Gout)

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22
Q

delta S=?

A

P+Gin-(ET+Q+Gout)

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23
Q

Fundamental form of the water balance equation??

A

P+/-Q+/-ET+/-DeltaS=0

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24
Q

Common expressions of the water balance equation?

A

P-Q-ET-DeltaS=0
Q=P-ET-DeltaS
P-(ET+Q)=0
P-Q=ET

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25
Q

What is evaporation?

A

Transferal of liquid water to gas water vapor, requires energy and water. Air must be dry enough to receive water vapor. Climate dictates available water and energy.

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26
Q

Types of evaporation?

A

Open water (Eo)-above a body of water, largest source at global scale.
Potential (PE)-overland, soil moistures.
Actual (Et)-amount of evaporation that occurs, PE>Et.

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27
Q

What is net radiation?

A

Amount of energy (Q*), sum of all heat fluxes at surface. Heat is required for evaporation. Sun heats the earth’s surface with short waves and long waves are reflected back into the atmosphere.

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28
Q

What is sensible heat flux?

A

Qs; heat we feel, measure

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29
Q

What is latent heat flux?

A

QL; heat absorbed/released.

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30
Q

What is soil heat flux?

A

Qg; heat released by soil ~0

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31
Q

What is Boyle’s law?

A

Sensible heat:latent heat. States that at constant temperature for a fixed mass, the absolute pressure and the volume of gas are inversely proportional.

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32
Q

What is the vapor pressure deficit?

A

The difference of moisture in the air and how much moisture the air can hold.

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33
Q

How do you calculate VPD?

A

Saturation vapor pressure-actual vapor pressure=VPD; the higher the VPD the more moisture the air can hold.

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34
Q

What is atmospheric mixing?

A

How well “wet” air diffuses into the atmosphere around it. More turbulent air is better.

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35
Q

What does ideal evaporation consist of?

A

Warm (high energy), dry, (high VPD), and windy (atmospheric mixing)

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36
Q

How does a forest canopy affect evaporation?

A

Evaporation from leaves, the ground, and plants. Interception loss; longer water stays on trees the more evaporation occurs. Water is intercepted by the canopy before reaching the ground.

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37
Q

Describe the relationship between interception loss and daily rainfall.

A

As daily rainfall increases interception quickly increases but then hits an asymptote because the canopy becomes saturated with water and the canopy has a limit on the amount of water it can hold.

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38
Q

What methods are there for estimating evaporation?

A

Thornthwaite, Turc, Penman, and Penman-Monteith.

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39
Q

Describe the Thornthwaite method

A

PE=16b(10t/I)^a
PE=potential evaporation
b=coefficient (given)
a=6.7x10^-7I^3 - 7.7x10^-5I^2+0.018I+0.49
t=average monthly temperature (mm)
I=annuanl heat index–> sum of i = (t/5)^1.514

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40
Q

Turc method for calculating PE

A

PE=p/sqrt(0.9+{P/l}^2)
P=annual precipitation (mm)
L=300+25T+0.05T^3
provides yearly estimates

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41
Q

Penman Method

A

Theoretical model for open water evaporation (Eo). Daily estimates mm/day. Requires-temperature, wind speed, vapor pressure, net radiation.

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42
Q

Penman revised

A

Evaporation over vegetated surface. Added aerodynamic resistance to equation (ra). Rougher canopy is more turbulent and therefore less resistance

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43
Q

Does stagnant air resist more than turbulent air?

A

Yes

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44
Q

Penman-Monteith method

A

Estimate actual evaporation (Et). Same as original Penman but with resistance term (rc)

45
Q

What keeps actual ET from equaling potential ET, especially in a temperate climate?

A

There are always unknowns that influence actual evaporation such as resistance from the atmosphere. It is difficult to measure all factors that influence ET.

46
Q

Actual vs. Potential evaporation

A

Availability of water dictates relationship between Et and PE. If you can measure soil moisture, you can figure out Et and PE.

47
Q

Forms of precipitation?

A

Rain, sleet, snow, hail, drizzle, graupel (small snow balls).

48
Q

How does temperature influence precipitation?

A

The ability of the air to hold water is temperature dependent. Cold air holds less, cooling of hot air releases water vapor.

49
Q

What are the three conditions needed for rainfall?

A

Cooling of atmosphere, condensation onto nuclei, growth of water/ice droplets.

50
Q

What is atmospheric cooling?

A

Cooling occurs as air rises. Air rises/cools due to: Convective precip, orographic precip, cyclonic precip, advection precip.

51
Q

What is Convective precipitation?

A

heating from surface

52
Q

What is orographic precipitation?

A

Rises over mountains. Causes air to rise quickly and therefore cool quickly dropping water on mountain.

53
Q

What is cyclonic precipitation?

A

weather system forces air upwards

54
Q

What is advection precipitation?

A

Warm cools over cold water. Lake snow effect.

55
Q

What is the condensation nuclei?

A

Minute particles floating in atmosphere generally less than a micron. Smoke, dust, salt, silver iodide, and potassium chloride

56
Q

How big must a water droplet grow before it becomes precipitation?

A

3,000 (3mm). Growth is needed to break air pressure.

57
Q

Five types of water droplet growth:

A

Condensation, sublimation (air to water), collision, coalescence (stick together through hydrostatic pressure like a magnet), Bergeron process (water leaves water and becomes ice).

58
Q

What is dewfall?

A

Type of advection. Vegetation is cooler than air and water condenses on leaves, grass, etc.

59
Q

Discuss the distribution of precipitation

A

Varies by location and time. Static (local) influences; altitude, aspect, slope. Dynamic (global); weather patterns, oceanic effects. Water is not evenly distributed due to topography. Steeper slope the longer it takes for clouds/precip to move over. Steeper slope will form rain quicker b/c of faster cooler.

60
Q

What is the rain shadow effect?

A

Leading edge of mountain range will receive more rainfall than trailing edge of range. West to east.

61
Q

What is throughfall?

A

Both direct and indirect forms. Basically, rain that passes through a canopy and reaches the ground.

62
Q

What is LAI?

A

Leaf area index- or the ratio of leaf area to ground surface area.

63
Q

What is the canopy storage capacity?

A

Volume of water stored before water drips. Precipitation intensity dependent.

64
Q

What is stem flow?

A

Precipitation flowing down tree trunk of plant stem into soil. <10% of rainfall transport. Amount depends on size of trunk/stem.

65
Q

What is interception loss?

A

Evaporation form leaves.

66
Q

What are three things to account for in regards to forest rainfall measurement?

A

Above canopy precipitation, through fall, and stem flow.

67
Q

What are the four main sources of error when measuring rainfall?

A

Losses due to evaporation, losses due to wetting of the gauge, over measurement due to splash from surrounding area, under-measurement due to turbulence around gauge.

68
Q

Is scale important for analyzing precipitation?

A

Yes, extremely. b/c rainfall is highly variable, even within the same watershed variation is high.

69
Q

Describe thiessen’s method for estimating rainfall

A

Spatial averaged rainfall. sum of all polygons rainfall*area/(total area of watershed). Split watershed into quantifiable units by splitting based on rain gauge location.

70
Q

Hypsometric method of estimating rainfall.

A

Same methods as thiessens, but divided based on contours. sum of all polygons rainfall*P. P=a/A.

71
Q

What is rainfall recurrence?

A

Probability that a storm will occur. Parameters needed include: Duration (length of event), intensity (rate in in/hr), return period (average time (yrs) expected between events.This is how to calculate 50yr events

72
Q

What is the Hazen method for calculating rainfall recurrence?

A 
Fa=100(2n-1)/2y
Fa=probability of occurrence (%Chance)
n=rank of events
y=total # of events
RI=Fa/100
73
Q

Rainfall distribution?

A

Rain varies over a single storm based on location and time. Smaller amount are more likely to occur than large amounts.

74
Q

How does rain effect water quality/quantity?

A

Major input into water budget. Improves water quality through dilution, but can also negatively effect through dissolution (acid rain).

75
Q

How is water stored?

A

Groundwater, snow and ice, Soil moisture, lakes/reservoirs

76
Q

Describe storage

A

Storage is not static. Water is not being held per say, but it is just being delay. A matter of transmission rate.

77
Q

What is the largest source of freshwater?

A

Ice and groundwater

78
Q

3 D’s of pollution

A

Dilution, dispersion, degradation.

79
Q

Types of groundwater storage?

A

saturated and unsaturated.

80
Q

What does the saturated zone refer to?

A

Phreatic zone.

81
Q

What is the phreatic zone?

A

Also known as the saturated zone. Exists below the water table.

82
Q

What is the Vadose zone?

A

unsaturated zone above the phreatic zone. Generally thought of as the water present in the soil and occurs above the water table.

83
Q

What does infiltration into the unsaturated zone depend on?

A

Water content of soil and transmissivity of water.

84
Q

How is soil water content quantified?

A

Volumetric content, gravimetric soil content, or saturated water content.

85
Q

How do you use volumetric moisture content to estimate the amount of water in the soil?

A

Relate to fraction of water in the total sample. Ratio is the final answer as volume units cancel out. Water/Vsoil

86
Q

How do you calculate soil moisture content gravimetrically?

A

Ratio of weight of water in soil to weight in sample. Can be related to volumetric soil content using soil bulk density (g/cm3).

87
Q

What is soil bulk density?

A

Mass of the dry soil to volume of the soil. Gives an indication of soil compaction

88
Q

What is porosity?

A

Fraction of pore space to total volume. Potential volumetric water content = 100% pore water. Never reach potential.

89
Q

What is field capacity?

A

stable saturation after drainage, before it starts over flowing, wet sponge before it starts dripping

90
Q

What is soil moisture deficit?

A

amount of water required (mm) to fill to capacity. If SMD > 0 overland flow will occur.

91
Q

What is wilting point?

A

soil water content necessary for plant life.

92
Q

What is hydraulic conductivity?

A

Ability of soil to transmit water through its pores. Wet soil flow controlled by saturated hydraulic conductivity.

93
Q

What is darcy’s law?

A 
calculate flow in a porous media. 
Q=AK(deltah/L
A=area
K=given coefficient
L=length of travel
Q=flow
94
Q

What is infiltration rate?

A

The rate at which water infiltrates the ground. Rates vary. Typically fast and then slows to a constant rate. Levels off at infiltration capacity.

95
Q

What is infiltration capacity?

A

Saturated hydraulic conductivity. When soil is fully saturated.

96
Q

What forces influence infiltration?

A

gravity and capillary action.

97
Q

What is capillary action?

A

Surface tension (liquid cohesion to itself), adsorption (static attraction to soil.

98
Q

What is the saturated zone?

A

The interface between soil water to groundwater. No evaporation, some transpiration, long residence time.

99
Q

What is an aquifer?

A

Layer of rock that is able to transmit/store water

Enough water for extraction.

100
Q

What is a an aquitard?

A

layer of rock that limits transmission of water, generally only applicable relevant to an aquifer.

101
Q

What is an aquiclude?

A

Layer of rock that restrict transmission of water.

102
Q

Types of confined aquifers?

A

Boundary above and below that restricts flow (aquitard) into a confined area.

103
Q

Types of unconfined aquifers?

A

no confining upper layer, horizontal and vertical flow. May have an area of confinement, often referred to as a perched aquifer.

104
Q

What is the groundwater-surface water exchange?

A

Groundwater feeds the base flow of many rivers, however, some rivers lose water to the groundwater table.

105
Q

How do you measure groundwater?

A

Gravimetric method: collect sample weigh it wet and then dry for 24hrs @ 105C, then weigh it again.

106
Q

What is the wilting point?

A

Soil moisture content when plants start to die.

107
Q

What is soil moisture deficit?

A

Amount of water required (mm of depth) to fill the soil up to field capacity.

108
Q

What is field capacity?

A

The stable point of saturation after rapid drainage.

Hydrology (2 decks)

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