Lecture Notes Flashcards
Hydrology
The study of water near the earth’s surface
Hydrogeology
Study of the interrelationships of geological material and processes with water. Subsurface issues
Why should we study hydrology
- Water is an important resource. It is increasingly in demand.
- There are many issues with the volume and quantity
- There are many issues with how to manage supplies of water as our climate changes
- The population is increasing which means there are more demands for water
Why is Chicago located where it is?
- Trade routes
* Small portage connecting the Great Lakes to the Mississippi
Ocean saline water
This water has zero fresh water in it
- about 97.2%
- 35 parts per thousand
- Saline does not just mean sodium and chlorine
Type of water in ice caps and glaciers
- Mostly freshwater
- 69% of the total freshwater in the world
- 2.14% of the total water
- problems-often frozen and in hard to reach places
Type of water in groundwater
- Mostly salty
- About .61% of earth’s total water
- About 30% of the world’s freshwater.
- The deeper you go into the ground the more dissolved materials that are present.
Surface water
- about .005% of earth’s total water
- Mostly freshwater
- .9% of total freshwater on earth
Atmospheric water
- .001% of earth’s total water
- Fresh water
- .1% of total freshwater on earth
How rapidly can water get exchanged between reservoirs?
It depends on the reservoir
*global ground water-1000s of years (very slow)
*global turnover atmospheric water-9 days (very quickly)
*global surface water-2-4 weeks
Varying time scales and volumes
(You don’t need to know exact numbers, just general ideas)
Residence time
total volume held is a reservoir/total flux in or out.
Units of residence time are simply in time
If a reservoir is well mixed what does the residence time give you
The average time expected for each water particle to spend there. (Every particle has the same probability of appearing anywhere in the reservoir)
Hydrologic cycle
Describes the storage and movement of water from one part of the earth to another
Ocean evaporation
Takes heat out of the ocean. As water turns from gas to liquid energy is also required.
Transpiration
plants release water during photosynthesis
Evapotranspiration
Evaporation and transpiration
What is meant by a steady state
Inputs are equal to outputs
The Aral sea
- Was a fairly large lake in the mountainous area of Asia
- A dry area without much precipitation, was fed by many rivers
- Most of the output was from evaporation
- Freshwarer coming into the lake system was diverted for agriculture
- About 90% of the surface area of the Aral sea was lost
- Sediments from under the lake caused a lot of pollution
- This lake no longer modifies climate
Mono Lake in California
- Snow from the mountains melted and ended up in mono lake
- There is a lot of volcanism in that area and the plates move relatively quickly
- This did not become and aral sea situation because there are laws in place that keep the water there
Percentage of world’s freshwater stored in the great lakes
21%
Percentage of America’s freshwater stored in the Great Lakes
84%
Drainage Basin
Also called a watershed or catchment
*Area that topographically appears to contribute water through a port of a stream.
What is the angle between hydrogens in a water molecule
105 percent
What types of bonds hold together water molecules
covalent
How does the melting and boiling point of water compare to other liquids?
It is relatively high due to hydrogen bonding.
Which is denser liquid water or water ice
Liquid water
Evaporation
break some of the hydrogen bonds and some molecules fly off into the air
What is always involved in phase changes
energy.
After evaporation remaining liquid water is cooler
What does the density of water depend on
Temperature, pressure, and chemical composition (In water this is salinity)
Pressure
The force applied perpindicular to the durface of an object. Measured in force per area.
pressure= force/area= mass*acceleration/area= N/m^2= Pa
Surface tension
why we get “nice little beads” hydrogen bonds holding molecules together. At the free surface H and O are not clinging to anything else. The net effect is an inward force at the surface that causes the water to act as if there is a membrane at the free surface of the water.
What produces capilarity?
surface tension
At what temperature is water at it’s maximum density?
About 4 degrees
Is warmer water lower or higher density than cold water.
Lower
Heat exchange
Heat added or removed as we go through different parts of the water cycle.
Specific heat
What is the amount of heat (H) that must be added to raise a unit mass (M) by a unit of temperature (T)?
Cp=H/(T*M)
How does the energy needed to increase liquid water compare to the energy needed to increase ice?
What are the implications of this?
You need 2x the energy to increase liquid that solid.
(This is why we use water to cool nuclear plants)
(This is why it is easier to get rid of glaciers)
Heat capacity
Specific heat*Objects mass measure in J/Deg C
What does it mean when we say water has a high thermal inertia?
Water tends to stay at about the same temperature unless a large amount of heat is added.
Latent heat
Energy lost or gained when an object undergoes a phase change at a constant temperature
Going from liquid to a solid
Heat is released.
Latent head of fusion
Going from a solid to a liquid
Heat is lost
Going from a liquid to a gas
Heat is lost latent heat of evaporation/vaporization
Sublimination
Ice-vapor. Solid directly to gas.
What are the different ways to measure evaporation?
- Class A evaporating pan. (National weather service standard)
- Lysimeter (Evapotranspirometer. Record precipitation and amount of water lost through soil)
- Atmometer (Measures loss of water from a wetted porous surface)
- Satellites0
What must you take into account when recording evaporation with a Class A evaporating pan
- Correction for the metal pan.
- If it is located in the sun or shade
- If it rains
- If the temperature is below freezing
- Insects (dying in the water or drinking the water)
Humidity
Amount of moisture in the air
Absolute humidity
Gram water/ M^3 air
Relative humidity
%absolute humidity/saturation humidity
Vapor pressure
Part of the air pressure due to the presence of water vapor. (Partial pressure)
How does the amount of water in the atmosphere change with temperature?
The higher the temperature the more water you can have.
Air density depends on
temperature
If an air mass gets warmer what happens to it?
It expands and can hold more water vapor.
As an air mass cools what hapens to it
It contracts, and it can not hold as much water vapor. If the water content does not change the relative humidity will increase
The dew point
The temperature to which air with a given water content and pressure needs to be cooled to reach saturation
What happens if the dew point is below freezing?
You get frost.
Hygrometer
Generic term for measuring humidity
What are different ways of measuring humidity?
- Sling psychrometer
- Digital psychrometer
- Satellites
What happens to airs ability to hold water as it rises?
It can hold less water
Cloud condensation nuclei
Very small about 1 micrometer. Required for the condensation of water molecules and precipitation.
Ways to measure precipitation
- Manual-rain gagues-have the issue of standardization
- Automated-rain gauges-measured by weight. (ex-tipping bucket)
- NASA/Japan/Europe Global precipitation measurement mission (This is good because it gives data over oceans)
Problems with rain gauges
- Heavy rain might swamp the system
- Rain gauges are only on land
- A lot of spacial bias
- Density of rain gauges reflects populations
How does surface area affect rates of evaporation?
- The larger the surface are the greater the evaporation
- Often larger lakes have a smaller difference in vapor pressure of the water surface and the air.
- Smaller lakes in general produce greater evaporation per surface area.
How does water salinity effect rates of evaporation?
The rate of evaporation is lower and higher salinity.
Salty water is held more tightly in liquid form by ionic attractions.
How does water depth affect the rate of evaporation?
If heat is going to deeper parts it might have less evaporation
How does the temperature of a lake affect the evaporation?
When the temperature of the lake is greater than the temperature of the air you can end up with a lot of evaporation.
(In summer lake levels are lower, and in the winter they are higher.)
Transpiration
- The result of plants.
- Requires absorption of water from the soil
- Water moves from the ground into the branches and the leaves of the plants.
- Eventually some evaporation from the leaves (through stomata)
phreatophytes
Plants with deep root systems. Draw a lot of water sometimes as deep as the water table.
Riperian areas
Areas on the bank of a river or stream.
Infiltration
Water that seeps into the ground that is into pervious soil. Becomes part of the base flow
Runoff
Total fow into the streams
Baseflow
Groundwater contributino to the stream
Overland flow
Enters the streams relatively rapidly.
Stream Hydrograph
A graph that describes runoff and other water input a stream.
Volumetric Gauging
A direct measurement. Divert streamflow to a container of a known volume and measure it
Water flux equation
Q=sum of the velocity*area
Techniques to find average velocity
Six Tenths depth Dilution gauging V-Notch Acoustic Doppler Current Profiler Gauges left in water
What affects the density of the snowpack
- Air temp
- Degree of separation (Idk what this means, look this up)
- Wind speed at the surface
Types of snowpack metamorphism
- Gravitational settling (Increase pressure by more efficient packing or particles)
- Destructive metamorphism (Sublimation at tips of snowflake)
- Constructive metamorphism (sintering, forms depth hoar)
- Melt metamorphism (Water introduced at surface sinks through snowpack and freezes. Disappearance of small grains and growth of large grains in the presence of liquid water.)
Depth hoar
Large low pressure ice crystals at base of snow pack. Forms when the rising water vapor condenses at colder portions of the snowpack)
Where is a snowpack the warmest?
Warmer at the bottom than at the top.
How does density change in a snowpack
Higher density on top, lower density on the bottom
Stages of melting snow
Warming phase (raises temperature to the melting point)
Ripening phase
Output phase
When you reach saturation what happens to evaporation?
Evaporation will continue when you first reach saturation because there are winds
Wind moves saturated air away and is replaced with drier air
Interception
Component of precipitation caught before it reaches the ground.
- Stored or returned to the atmosphere before it can get involved in other parts of the hydrologic cycle
- Can account for as much as 40-50% of gross rainfall.
- Depends on vegetation cover
- slows passage of water to the ground and changes the way water interacts with soil, plants and the atmosphere
Depression storage
puddles
Evaporation
surface and near surface water that becomes water vapor. Quiet and more or less continuous. Difficult to measure.
How can evaporation effect the quality of a body of water
Can increase salt concentrations and other contaminants
Salton Sea
- Naturally depressed are in California.
- Too salty for humans, but can be used for agriculture and some livestock.
- Because of change of Colorado river it has become quite salty
- Toxins have gone up as well, and plants and birds are dying there.
- People are trying to save the Salton sea
- is it worth it?
Gross precipitation-
that which would be measured out in the open.
Throughfall
Precipitation that passes through the foliage or drops through the canopy.
Stemflow
Water that falls down the branches and trunks of plants
Canopy interception
Water that hits the canopy and is held and evaporated back into the atmosphere
Litter interception
Water that is captured temporarily near the ground surface on plant and leaf litter and then evaporates back to the atmosphere
Net rainfall
Rainfall that reaches the ground
Formula for snowmelt
B(Ta-Tm)
Where b is the melt coefficient and TA is the airtemp and m is the base temp
IET
interception, evaporation, transpiration
Factors for evaporation
Temperature (higher temp easier to break hydrogen bonds) Energy (mostly solar0 Wind Temperature at air/water interface Humidity in overlying air Dissolved material in the water (saltier warder is harder to evaporate) Depth of the water Size of the water surface (fetch) Moisture in soil
Ripening phase
Melting occurs, but water is retained. A snow paack is ripe when it’s isothermal at zero deg C and cannot hold any water
Ways to measure snow
Gauges (stick,snow tube, snow pillow)
Equipment using gamma rays
*Cannot get numbers as acurate or precise as with rain.
How do wind speeds affect density of snow?
calm-less dense
windy-more dense
factors that contribute to snowpack melting?
compaction surface area insolation humidity albedo what the pile of snow is on (pavement?)
How does temperature affect the density of the snowpack?
The warmer it is the more dense the snow.
Formula for peak runoff rate
Q equals CIA
Where Q is the peak runoff rate, C is a unit-less runoff coefficient, I is the average rainfall intensity in L/T
A is drainage area in L^2
Rational Equation
If it rains for a long enough period than the peak Q from basin will be the average rate of rain x basin are (with an adjustment by a factor to account for infiltration)
Q equals CIA
order the following from lowest to high C
- Cemetary or park
- downtown area
- sandy soil
sandy soil
- cemetary or park
- downtown area
surface tension
why we get “nice little beads” of water. Hydrogen bonds holding molecules together at the free surface of water are not clinging to anything else. Net effect is an inward force at the surface. Causes the water to act as if there is a membrane at the free surface of the water.
heat exchange
head added or removed as we go through different parts of the water cycle.
Gas water to solid water
deposition
equation to determine the flux
Q equals the sum of Vi*Ai
Where Vi equals velocity and Ai equals the area
In what direction should a cross section be taken?
A cross section should be parallel to the dominant velocity vector.
Six tenths depth menthods
Choose 2 fixed spots 20% and 80% define constants and get the average velocity
The snow melt energy science appropach
Measure all inputs and outputs of energy of mass (As was done in our lab)
The snow melt temperature Index approach
Uses conceptual models and empirical relationships.
Aquafer
A geological unit that can store enough water and transmit it at a rate fat enough to be significant
Challenges of overuse if aquifers
Pumping costs go up
Land subsidence
Less water
Takes a longtime to recover
Major types of aquifers
Unconscious ares/semi consolidated
Sandstone
Carbonate rock
Igneous and metamorphic rocks
In general do rounded or angular grains leave more room for water
Angular
Uniform coefficient for measuring sorting
Cu=d90/d10
Look at ten and sixty percent of the grain distribution curve.
If cu is less than four it is well sorted
If cu is bigger than 6 it is poorly sorted
What does compaction and dis genesis do I porosity
It decreased it. Because of I filling of pores with cement and pressure
How do igneous and metamorphic rocks form aquafers?
As volcanic rocks cool they shrink and cracks form,also has bubbles leave holes
