Surface Water 1 - Rivers, lakes, marshes etc. Flashcards
Wetlands
- Nutrient rich
- Biodiversity
- Water reservoir
- Carbon Storage
Marshes
- Wet most of the time
- Grassy or reedy vegetation
- Can be salty (tidal marsh) or fresh
- Most common wetland in NA
Swamps
- Woody plants, often treed
- Deeper water (often >1m)
- Nutrient rich
- ex. Mangroves
Bogs
- Water from precipitation
- Thick mat of vegetation (peat) rather than soil
- Acidic
- Soft, spongy, organic
Fens
- Like bogs but fed from GW
- More nutrients
- More neutral pH
- Often associated with glacial kettles
- Also peatlands
Marsh description quote
- Land where excess water is the dominant factor determining the nature of soil development and the types of animals and plant communities living at the soil surface
- It spans a continuum of environments where terrestrial and aquatic systems intergrade
Emissions from degrading/disturbed peat
- Greater than the stores of peat
- Changes carbon budget
Global peatlands
- Canada has greatest stores, next is Russia
- Indonesia and Russia degrade the most peat
Peatlands and wetlands
- Peatlands cover 12% of Canada (1.2 x 10^6 km^2)
- Wetlands cover 14% of Canada (1.4 x 10^6 km^2)
- 14% of global wetlands in Canada
- 6% of global land surface is wetland, Canada is much wetter than the average
Lakes and Rivers in Canada
Lakes: - Uncounted, more than 32,000 - Most less than 100 km^2 - 7> 10,000 km^2 Rivers: - Uncounted, 1000's
Canadian Great Lakes
- Moderate climate and affect precipitation
- Almost froze 100% in 2014 due to polar vortex (last time this was seen was 1980)
- 2014 was anomalous year due to el nino
- % ice cover depends on location of jet stream
Where is the largest surface water storage on the planet?
- Lake Baikal, Russia
- Very deep, 1637 m
- 1700 species, 2/3 only found here
- UNESCO site in 1998
How much water does Lake Baikal hold?
- 20% of world’s lake water
What is the trend seen in Lake Baikal’s ice?
- Freeze dates may be cyclical or have a negative trend and freeze later
- Break up date may have positive trend, but also shows cyclical pattern
Which lakes from Canada drain into the Gulf of Mexico?
- a few in AB and SK on the border of the U.S
Where does most of Canada’s surface water drain?
The Hudson Bay, followed closely by the Arctic Ocean
What is the largest river in Canada?
- Mackenzie River, closely followed by St. Lawrence (more discharge but less length)
What are the 2 types of water flow?
- Laminar (steady)
- Turbulent (unsteady)
Laminar flow
- Smooth
- Less friction
- Less likely on surface water
- Semi-likely in GW but only as long as substrate doesn’t change
- Likely in pipes, artificial flow
Forces involved in water flow
- Gravity: Moves water down rivers, drives conversion of potential to kinetic energy/inertia
- Friction: Resists water flow
Where is the flow in a river the fastest?
- Where the water height is greatest, just below the surface and away from the banks (friction)
Reynolds Number, Re
- Measure of turbulence
- Turbulent flow Re>2000, Laminar Re
Froude Number, Fr
- Fr = v/vw = stream flow velocity/sqrt(gravity*Height of water)
- Tells which way a wave will propagate, will water flow downstream
Subcritical Froude number
- Fr
Critical Froude number
Fr = 1
- V=Vw, flow velocity equals surface wave velocity
- wave goes slightly downstream
- Hydraulic jumping
Supercritical Froude number
Fr > 1
- V>Vw, flow velocity greater than surface wave velocity
- Fast downstream movement, hydraulic jumping
- Laminar flow
What causes change in river flow?
- slope
- frictional resistance of channel
- inputs or outputs
- size and shape of channel (narrowing/expanding)
- change in elevation (waterfall)
What is stage?
Stage = Water level
- Discharge is a function of stage
How is stage measured?
- With a shelter house with intake pipes that draw water into stilling well and a float on the surface gives height of river
How does a shelter house work?
- Measures stage
- Can remotely send data on river height out
- Remote data can have errors and may not report true stage
- Remote updates are important, especially in flood prone and large rivers
- Like a tide gauge, float in a stilling well measures height
What are some problems with shelter houses?
- Remote data can have issues, still needs staff power to check on
- Ex. Assiniboine river had large runoff that wasn’t noticed in time before it reached cities, error in shelter house data
How is discharge measured?
- Velocity-area method
- Tracer Dilution
- Float Method
What is the float method of measuring discharge?
- Toss a floating object into the stream and measure time it takes to travel a distance
- Accounts for 85% of deeper velocity (friction makes surface slower)
- Used when sediments/debris could bounce up and damage a current meter
What is the velocity-area method of measuring discharge?
- Split stream into sections, measure velocity in each, take average of measurements
- Max velocity is probably near surface in the middle of the stream
- Q = A x V or (width x depth) x Velocity
- Q increases with increasing depth, width, and velocity
What is the tracer-dilution method of measuring discharge?
- Injection of a solution into a stream, then measure when it is detected downstream
What are the 2 methods of tracer-dilution?
- 2 methods (constant solution and dump solution)
What are some considerations when using the tracer-dilution method?
- Water movement (stagnant vs rapid)
- Injection solution behaviour
How does a weir work?
- Used to create critical conditions (Fr = 1)
- Gives a simple, known geometry to help calculate discharge
Hydrograph Baseflow
- Water present in a stream that is not related to precipitation
- GW contribution is likely
- No overland flow contribution to baseflow
Hydrograph Baseflow Recession
- Can be a straight-line leading to precipitation event or naturally decreasing due to stream characteristics
Hydrograph Rising Limb
- Response to input water causes hydrograph discharge to increase
Hydrograph Peak
- Most of the water from a precipitation event has reached the stream at this point
- Discharge will decrease after this point
Hydrograph Quickflow
- Water makes its way to the stream quickly
- Overland flow contribution to stream
- Input water contribution that is not from base flow
Hydrograph Falling Limb
- Quickflow recession
- Decreases from peak
Hydrograph Separation Point
- Point where quick flow is done and returns to base flow
What are hydrographs?
- Used to show response of a stream discharge to precipitation events
Storm Hydrograph
- Translation: Temporal shift
- Attenuation: Dampening of peak height due to storage in the basin
- Peak looks prolonged and peak discharge is less, takes longer to return to normal
Annual Hydrograph
- Precipitation bar graph on secondary axis
- Shows a relationship between precipitation events and discharge
What does hydrograph character depend on?
- Precipitation characteristics (magnitude, intensity, duration, distribution, phase)
- Basin characteristics (slope angle, slope shape, soil type, soil thickness, initial soil moisture conditions, anthropogenic impacts, basin size, basin shape)
Unit Hydrograph
- Predictions for type of response likely in a stream from precip events
- Specific to a certain stream
- Used to predict discharge and floods
- Can get volume of runoff expected
Hydrograph response to dams
- Discharge greatly decreases
- More even discharge, peaks not very pronounced
What are the 3 mechanisms of fluvial transport?
- Advection
- Diffusion
- Dispersion
Advection
- Movement of a tracer resulting from the current (mean flow of water)
- Calculated from the product of velocity and tracer concentration
Advection Flux
Amount of tracer transported per unit time, per unit area perpendicular to current
Diffusion
Tracer mixing and spreading from random molecular motion within fluid
What are the 2 types of diffusion?
Turbulent and Molecular
Molecular Diffusion
Fick’s Law
- Gradient diffusion law for concentration
- Goes from high to low
Turbulent Diffusion
Mixing due to turbulent motions in the river or lake
- Scale dependent
Dispersion
Mixing due to velocity gradients in fluid (shear dispersion)
- Differing dispersion and concentration in areas of different velocities
What are some potential sources of loss for tracer solution?
- Temporary storage
- Decay or sorption of solute
What are the 2 main methods of stream order designation?
- Shreve
- Strahler
Stream order
- Hierarchy of channels from 1st order to nth order main channel
Strahler Stream order method
- Junction of 2 streams of order x form next downstream order of ‘x + 1’
- Junction of 2 streams of different orders x and y, where y>x creates order equal to higher order stream y
Shreve Stream order method
- Junction of 2 streams of order x or 2 streams of order x and y, form next downstream order of ‘x + y’
