Water Hydrology and Streams Flashcards
Hydrologic cycle
movement of water between hydrosphere (ocean), atmosphere (air), and lithosphere (land)
Hydrologic processes (5 points)
- Evaporation
- precipitation
- infiltration
- evapotranspiration
- runoff (streams)
runofff
part of precipitation that does not infiltrate or re-evaporate, that is collected by stream.
Annual water balance
-stream runoff (mm/annum)= imput-losses
(imput=rain and snow, losses=evapotranspiration)
-storage (changes in volume of soil, or lake/river water
steady state
imput=output
no increase in reservoir size
Residence time
volume/imput
1 km^2= xm^2?
1 km^2 = 1*10^6 m^2
Examples f residence times:
H2O in atmosphere: A few days
H2O in lake ON: 6.4-9 yrs
Ground H2O in deep aquifer: 100s-1000s of yrs
Sea water in ocean: ~3200 yrs
What happens when imput is greater than output? (2 points)
- flooding
- ships can carry more cargo without grounding
What happens when loss is greater than precipitation imput? (5 points)
- drop in water levele
- increase in salinity
- soil dries up
- wind born soil transport increases
- agricultural failure
Define stream
- any flowing body of water
- most important eroding agent and main function of sediment transport
Define river
major branch of a stream system
Importance of streams
- major agents of change in landscapes
- provided pathways for colonists
- most cities are buit around a river (source of drinking water)
- agriculture
- recreation
Stream System components
- Drainage basin
- tributary
- drainage divide
Drainage Basin
total area drained by stream and its tributaries
Tributaries
Small stream flowing into larger (small stream conTRIBUTES to larger)
Drainage divide
ridge of high ground dividing one drainage basin from another
Largest Drainage basins in North America?
1) Mississippi (3.2 million km2)
2) Mackenzie (1.8 million km2)
Largest Drain Basin globally?
The Amazon river (6 million km2)
Define headwaters and mouth
- headwaters=source
- mouth is where river enters open water
Stream system components
- Valleys: sloping area around stream
- channel: bottom of valley where water flows
- floodplains: flat area in valley level with top of channel. (can be flooded)
Define Gradient (L)
change in height/distance (cm-m/km)
-decreases as you go downstream
Define Discharge (Q) (m3/s)
=velocity (U) (m/s)/area (m2)
-increases downstream due to collection from tributaries
Depth (d) and Width (w)
channel size INCREASES downstream
-increased area (A)= decresed friction; larger streams have greater velocity (U)
velocity (U) (m/s)
U increases downstream; less bed roughness, higher Q, larger channels
What is the purpose of a stream?
plane out relief via channelized flow (most efficient)
How does a stream plane out relief via channelized flow? (3 things)
1) erosion
2) transport
3) deposition
What controls erosion, transport, and and deposition? (3 things)
1) hydraulic parameters:
-flow velocity, discharge, viscosity
(volume of water flowing through channel and the velocity at which it does so)
2) morphology
(ie. Fast flowing cascade in mountains vs long, sinuous river in plains
3) material (that its eroding into or transporting)
(ie. eroding into granit vs loose sediment; transporting large boulders vs sand)
modes of sediment transport (4)
- Bedload (along the bed)
- Saltation (periodically lifts off into flow)
- suspension (in the flow)
- solution (dissolved in flow)
True or False: Grain size transported by stream is directly proportional to stream velocity
true
What law describes the forces of buoyancy and friction (drag due to flow)
Stoke’s Law
True or False, particles settle when F(gravity)>(Fbuoy+Fdrag)
true
F(gravity)
=m(particle)*g
=Volume(particle)Density(particle)g
Fluid Buoyancy Force
=Volume(p)Density(p)g
Force G-B
=V(p)(D(p)-D(f))g
Fluid Drag Force
Drag=0.5CD(fluid)R(p)^2*W^2
C is a drag coefficient, R(p) is particle radius, W is water velocity, and D(f) is fluid density
Base level
- level below which stream cannot erode.
- changes in base level result in changes in the longitudinal profile
Graded stream
equilibrium state where stream can transport its load without deposition or erosion
What happens to longitudinal profile following an increase in base level?
increase in deposition
What happens to longitudinal profile following a decrease in base level?
- increased erosion
- increased transport
Channel patterns
1) braided
2) meandering
Braided rivers
- rapid and irregular discharge
- higher slopes
- erodible banks
- rapid channel migration
- abundant coarse sediment
- in-channel bars (lense of sediment)
- little overbank preservation
- poorly developed levees
- lateral accretion deposits uncommon
Meandering Rivers
- lower and more regular discharge
- lower slopes
- cohesive banks (less likely to erode)
- slower, more regular channel migration
- abundant fine sediment
- extensive overbank preservation
- well developed levees
- few inchannel bars
- lateral accretion deposits common
What is a consequence of secondary flow?
point bars (deposits along inner bank
helicoidal flow
response to secondary flow (cross channel flow) pressure gradient established by pile up of water in outer bank from centrifugal force and downstream flow
Causes of floods (3)
1) high precipitation over short amount of time
2) ice jam
3) dam and artificial levees
Factors contributing to floods (2)
1) low infiltration rate (bedrock, saturated soil, frozen ground, cities)=high runoff rate
2) topography (flat area, funnelling effect)
Impacts of flooding (3 main points)
Human consequences
- loss of life
- disease
- water contamination
Material impact
-destruction or damage to property and infrastructures
Landscape
- erosion (high discharge)
- sedimentation (reduced velocity–>channel invades floodplain)
- avulsion (abandonment of old channel for new one)
Flood controls (5 things)
- artificial levees (must be continually built up as river deposits more due to inability to flood)
- dams
- channelization
- natural storage areas
- live elsewhere
