Hydrology

WHEN WRITING DECIMALS, ALWAYS PUT A 0 IN FRONT IF THERE ARE NO OTHER DIGITS; 0.5 NOT .

the degree or fineness of a measurement

Q = V*A

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

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)

life, manufacturing, cooling systems (nuclear), solvent, agriculture, transportation, electricity (turbines), politically/weapon (cut off water supply), cooking, disinfect (boiling), modifies climate via heat transfer

the attraction of H to O between the positively charges end of one molecule (H) and the negatively charged end of another (O)

• +H
• -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

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

gas to solid to liquid

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

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

when water is heated above 100, more heat is needed to cause the water to evaporate

when water is cooled to 0, more heat must be removed to form ice

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)

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.

because of cohesion, water has a high surface tension, or high resistance to penetration or stretching of the surface

formation of waves

suporting surface for organisms

water fills pore space; gives soil its look

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

due to the marked polarity of the water molecule and its tendency to form hydrogen bonds with other molecules.

• 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

main power source is the sun

gravity adds some energy along with humans

plants add energy when burned as wood

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

P - Q = ET

• 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

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

• Model Error
• Change in Storage might be 0
• Gin/out might be negligble
• Measurement Error
• P/Q/ET/etc might not be accurate

precip gauges are unevenlly distributed over any given region, therefore sample is technically unrepresentative

cant put buckets everywhere

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

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

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)

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)

process by which electromagnetic energy emits from an object

hotter the body, more intens radiation, the shorter the wavelength

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

the transfer of heat by a MOVING SUBSTANCE

molecules actually move from one place to another

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

• 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

latitude

altitude

slope

topography

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

• 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

• 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

Adiabatic cooling is due to change in density/pressure without an addition or loss of heat

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

resulting from air being forced upward in a low pressure system

air pushed together can only go up


---------->>>>> ^ <<<<<<------------

resulting from the lifting of air masses due to topography

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

• 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

• weather
• flood prediction
• event planning
• agriculture
• water supplies
• buildig structures
• recreation

wind

gauge may be functionally incorrectly

plain and simple human error

trees/buildings

splash

evaporation

water on sides and top of gauges

• per day
• per hour
• per month
• per year

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

------

allows for uneven distributions of stations

allows for inclusion of stations not in basisn

words well for high topographic regions

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

amount of rain

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

how long the rainfall even lasts or period of rainfall you are interested in

how long does it last for

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

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?

the degree that further measurements or calculations will show the same or similar results

• 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

planning for urban areas

agriculture

flood mitigation

structure; design

water supply

Probable Max Precip/Flood

the greatest depth of P for a given period that is physically possible over a given storm

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

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

-------

*gives the N anual precip values according to size

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

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"

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