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Decimals
WHEN WRITING DECIMALS, ALWAYS PUT A 0 IN FRONT IF THERE ARE NO OTHER DIGITS; 0.5 NOT .
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Precision
the degree or fineness of a measurement
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Discharge Equation
Q = V*A
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hydrology
the geoscience that describes and predicts the occurrence, circulation, and distribution of the water of the earth and its atmosphere
- concerned with the land phase of the hydro cycle
- the distribution (and storage) of water on the surface and beneath the surface, and the physical, chemical and biological interactions with the materials of the earth and the living things on it.
fresh water is the main concern but salt is not forgotten
concerned with enginering to find solutions to problems posed by water
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Hydro Cycle
Model
Conservative quantity
the distribution and spatial and temporal variations of water substance in the terrestrial, oceanic, and atmospheric compartments of the global water system.
A conceptual model of how water moves around between the Earth and the atmosphere in different states (gas, liquid, solid).
A conservative quantity is one that cannot be created or destroyed within the system. (don't gain or lose in total, its just moves from one thing to the next)
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Why the Hydro Cycle is important
life, manufacturing, cooling systems (nuclear), solvent, agriculture, transportation, electricity (turbines), politically/weapon (cut off water supply), cooking, disinfect (boiling), modifies climate via heat transfer
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Hydrogen Bonding
the attraction of H to O between the positively charges end of one molecule (H) and the negatively charged end of another (O)
the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond. These bonds can occur between molecules (intermolecularly), or within different parts of a single molecule
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Heating Water
Cooling Water
high additions of energy cause the eventually breaking down of all hydrogen bonds till evaporation occurs
the energy is so low that the hydro bonds lock together the molecules into 3D crystals of ice
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Less dense to more dense from...
gas to solid to liquid
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Heat Capacity
the amound of energy needed to raise 1 gram of water 1 degree C
water has a high heat capacity meaning it changes temperatures slowly
important due to lakes heat/cool slower than land
resistant to sudden changes in tempo
moderate the earth temp
acts as a coolant/heater during sudden temp changes
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Latent Heat
the energy absorbed or released during a change of state
when a solid turns into a liquid (v.v) energy must be supplied to stop it from being a solid.
this energy, supplied externally does not bring about a change in temp
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latent heat of vaporization
when water is heated above 100, more heat is needed to cause the water to evaporate
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latent heat of fusion
when water is cooled to 0, more heat must be removed to form ice
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Viscosity
the resistance of a liquid to motion
- low - warm - fast flow
- high - cold - slow flow
important to marine life
causes small animals/plants to not sink
allows for liquid to flow through pipes easily (oil ex)
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Cohesion
the action or property of like molecules sticking together, being mutually attractive. This is an intrinsic property of asubstance that is caused by the shape and structure of its molecules which makes the distribution of orbitingelectrons irregular when molecules get close to one another, creating electrical attraction that can maintain a macroscopic structure such as a water drop.
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Surface Tension
because of cohesion, water has a high surface tension, or high resistance to penetration or stretching of the surface
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Cohesion/Surface Tension importance
formation of waves
suporting surface for organisms
water fills pore space; gives soil its look
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Capillarity
the ability of a narrow tube to draw a liquid upwards against the force of gravity
importants cause it is responsible for moving goundwater from wet areas to dry areas
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Universal Solevant of Water ???
due to the marked polarity of the water molecule and its tendency to form hydrogen bonds with other molecules.
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What is water solevency good for
- Vital reactions in living organisms occur in water
- Living organisms receive nourishment through food dissolved in water
- Water dissolves chemicals from rocks and adds them to the soil and lakes, rivers, and the ocean
- Water also dissolves and makes available substances essential to marine organisms, like fertilizers and carbon dioxide (for plants) and oxygen (for animals)
- Coke, Pepsi, sweet drinks
- Dissolves statues, buildings, other things we make and expose to water
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What powers the Hydro cycle
main power source is the sun
gravity adds some energy along with humans
plants add energy when burned as wood
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Water Balence Equation
A mathematical description of the processes operating within a given timeframe that incorporates principles of mass and energy continuity.
P + Gin - (Q+ ET + Gout) = change in S
- Precipitation
- Ground Water In Out
- Discharge
- Evapotranspiration
- Storage
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Input - Output = Change in Storage
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Evapotranspiration Equation
P - Q = ET
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You have an uncovered swimming pool (20 ft * 20 ft * 6 ft) with a leak at the bottom. You want to know how much water you are losing in ft3 /day and in gallons per day . (Water costs money).
After 10 days, the water is 60 in deep.
Over the 10 days, the evaporation adds up to 3 in. Rainfall going in is 1 in.
What is your water loss in in? In ft?
- 12 inches - 3 inches + 1 inch =
- loss of 10 incheschange
- 0.83 ft in
- 1 inch a day/.08 ft a day depth
Change in Volume
- [(10 in) * (1 ft/12in) * (20 ft) * (20ft)
- = 33.3 ft^3 per day
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Watershed
the area of land that drains water, sediment, and disolved materials to a common outlet at some point along a stream channel
An area surrounded by a continuous topographic divide within which all runoff joins and single stream and extends downstream to the point that the stream crosses the divide.
The area that appears on the basis of topography to contribute all the water that passes through a given cross section of a stream
The surface trace of the boundary that delimits a watershed is called the divide.
A watershed is a natural landscape unit
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Errors with WBE
- Model Error
- Change in Storage might be 0
- Gin/out might be negligble
- Measurement Error
- P/Q/ET/etc might not be accurate
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Spatial Variability
precip gauges are unevenlly distributed over any given region, therefore sample is technically unrepresentative
cant put buckets everywhere
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Temporal Variability
Y
inputs, storage, and outputs are all time distributed variables; they vary over time
stream flow is highly variable, causing estimates to be off, causing problems with management
Y
- It depends on season
- It depends on daily P (even within one day)
- It depends on groundwater flow
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Time Series
EX
discrete sequence of values with each value assigned to a particular time in the sequence
EX) the number of days with moer than 1 mm rain in each year at a particular place
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Flow Duration Curve
Y
The flow duration curve is a plot that shows the percentage of time that flow in a stream is likely to equal or exceed some specified value of interest.
- FDC concerned with the amount of time a certain flow is exceeded
- Use daily mean flow (average for each day) NOT
- Mean daily flow (average of a series of daily flows)
- More than 5 years usually needed
Y
Range of flows and their frequency (how often)
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how is the earth heated
70% comes from the earths surface
30% comes from solar radiation
earth is warmed from BELOW
suns incoming shortwave radiation is transformed to longwave radiation after hitting the earth and bouncing back into the atmosphere (GREENHOUSE)
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Radiation
process by which electromagnetic energy emits from an object
hotter the body, more intens radiation, the shorter the wavelength
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Conduction
the movement of energy from one molecule to another WITHOUT CHANGES in the relative positions of the molecules
EX) movement of heat from metal to hand to brain to cussing
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Convection
the transfer of heat by a MOVING SUBSTANCE
molecules actually move from one place to another
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what causes season
tilt of the earth
the seasons are caused by the contrasts in the solar radiation receipts as the north and southern hemisphere are alternately tilted toward (summer) and away from (winter) the sun
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What causes wind to blow?
- heating of the earth…causing a difference in pressure
- cold air is more weight creating more pressure
- vice versa
- high pressure goes clockwise and outward and spreading out
- vice versa
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what factors affect global distribution of precipitation
latitude
altitude
slope
topography
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teleconnection
a climatic anomaly that is a distant consequence of another climatic anomaly
EX) ENSO
El Nino Southern Oscillation
warm phase - abnormally high sea surface temp occur along with low pressure in eastern pacific and high pressure in western pacific
this shift can ause droughts, unusually cold/warm winters, torrential (heavy,violent) rains
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3 types of sediment load carried by rivers
- disolved
- product of chemical weathering
- suspended
- fine particles carried long distances
- small
- largest fraction of the sediment being carried
- bed
- particles moved along by rolling, sliding, or saltation
- BIG
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Types of Precip
- Drizzle
- fine mist
- low intensity
- Rain
- all liquid heaver than drizzle
- low to moderate to high intensity
- Sleet
- rain that freezes as it falls
- Freezing Rain
- supercooled rain falling on surfaces that are below freezing
- Snow
- ice crystals that reach the ground as single or joined together crystals as snow flakes
- Hail
- round lumps of ice
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Adiabatic cooling
Adiabatic cooling is due to change in density/pressure without an addition or loss of heat
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Convectional Lifting
as earth is heated by the sun, bubbles of hot air (thermals) rise upward from the warm surface
a thermal cools as it rises and becomes diluted as it mixes with the surrounding air
the moisture condenses and is visible as a cloud
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Convergent Lifting
resulting from air being forced upward in a low pressure system
air pushed together can only go up
---------->>>>> ^ <<<<<<------------
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Oragraphic Lifting
resulting from the lifting of air masses due to topography
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Cyclonic Lifting
low pressure system
air rushes into the low and rises, expecially if air is warm and moist
Non-frontal convergence
ITCZ – converging trade winds lead to lifting and condensation
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Factors causing precip distributions of time
- seasonal variations
- huricane seasons
- mid lat regions
- longterm variations
- periods of drought
- movement of fronts
- on/off shore winds
- mountain/valley winds
- wind/storm speed
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uses of precip data
- weather
- flood prediction
- event planning
- agriculture
- water supplies
- buildig structures
- recreation
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why is it hard measuring snow/rain
wind
gauge may be functionally incorrectly
plain and simple human error
trees/buildings
splash
evaporation
water on sides and top of gauges
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what times scales are we interested in
- per day
- per hour
- per month
- per year
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Theissen Polygons
plot gauges
draw lines conecting stations
draw lines perpindicular through the midpoint of each line
measure each area and express it a a percent of the basin
add to get average
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allows for uneven distributions of stations
allows for inclusion of stations not in basisn
words well for high topographic regions
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Isohytel
most accurate
plot gauges
draw lines of equal rainfall
find averages between lines
find area; express as a %
multiply by rainfall
add both to get average
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Intensity
rainfall per unit of time
How much rain we can expect during a 30-minute, 1 hour, 6 hour, 24 hour storm
rate/time ex) 1 inch per hour
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Duration
how long the rainfall even lasts or period of rainfall you are interested in
how long does it last for
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Frequency
how often an event occurs
- How often a certain amount of rainfall is likely to occur
- Based on the probable occurrence of such a rainfall in a given year
- e.g. a 2-yr rainfall has a 50% chance of occurring in a given year or once every 2 years
- e.g. a 100-yr rainfall has a 1% chance of occurring in a given year or once every 100 years
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Accuracy
factors causing inaccuracy
the degree of conformity of a measured/calculated quantity to its actual (true) value
inaccuracy:
- What size should the orifice (opening) be?
- How should the orifice be oriented?
- How much should the gage protrude above the ground surface?
- Should the gage have a wind shield?
- How far should the gage be from trees, buildings, etc.?
- How can we prevent water from splashing in or out?
- How about evaporation?
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Precision
the degree that further measurements or calculations will show the same or similar results
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Rain Gauges Common Errors
- Losses due to evaporation
- Losses due to wetting of the gage
- Over-measurement due to splash from surrounding area
- Under-measurement due to turbulence around the gage
- Instrument error
- Human error
- There are about 13,000 gages sites in the US
- 10,000 non-recording and 3000 recording
- They are maintained by professionals at weather stations and by unpaid observers at many other sites
- On average, each station represents about 235 sq mi
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Anual seasonal averages are good for what
planning for urban areas
agriculture
flood mitigation
structure; design
water supply
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PMP/F
Probable Max Precip/Flood
the greatest depth of P for a given period that is physically possible over a given storm
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PMP/F estimation
examine rainfall data for largest flood in and near the region of interest
estimate the combo of conditions that could have produced the rainfall
uses PMP maps based on meterological analysis
storm size based on basin size/duration/intensity
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Cumulative Frequecny Distribution
Fi = (m(n+1) *100
Fi - % of years with a rainfall less than or equal than the particular rainfall
M - smallest rainfall; then up...
N - number of values you have
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*gives the N anual precip values according to size
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IDF
Intensity Duration Frequency Analysis
T = 1/p = (n+1)/M
T - recurrence interval (return period) - average interval between events greater than or equal to a given magniuted; expressed in years
P - probability that the anual max will be equal to or greater
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IDF EX
10 year range
24 hour max is 8 inches
on average, 1/10 years, you will have 8 inches of rain
Recurrance Interval is the "1/10 years"
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What problems can we encounter when we use IDF? What factors do we have to consider?
problems; but no other method to use with current technology
1) extrapolating to periods longer than we have data for can lead to large errors
estimating only events with a return period no longer than the length of the record is best but often estimates for long periods are needed despite lack of data
using a small sample size is not a good thing
2) This approach does not take climatic change into consideration
the probabilities we calculate using the sample may not represent the actual population
climate changes; next 30 years could be different, so using the previous 30 years data is useless
3) due to persistence in the climate, data points might not be independent
assumptions is its independent
4) use of different data samples (periods) gives different results. Which is true?
changing the period changes the data
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