Surface Water Flashcards
Water covers 71% of Earth’s surface and is the dominant agent governing:
environmental processes
Top 3 countries with surface water:
- Brazil
- Russia
- Canada (mostly in Arctic though)
Water Use in Canada
most of our water use is for energy generation and industrial purposes: 58% thermal power gen, 18% manufacturing, 10% municipal, 8% agriculture, 4% mining
What is the Hydrologic Cycle?
The transfer of water between the atmosphere, the ocean, lakes and stream and the crust (as groundwater)
What is a stream?
any water that runs in a channel
What is a river?
a large stream, although no specific size cut-off for a “river”
Runoff enters channels that join other channels to form:
a drainage system (network of channels, sends water downhill)
What is the watershed?
The total area feeding water to a stream
First-order, second-order, third-order, fourth-order basins depend on:
how far from the source, first is almost the source (headwater), 1-4 is in the mountains/steep
Drainage Patterns
Dendritic: looks like nerve ends
Radial: isolated high point with circular drainage, volcanoes -> stratovolcano
Trellis: parallel sheets, in Rocky mountains
Rectangular: looks like brain wrinkles
Stream Discharge
The volume of water passing a point in a specific amount of time i.e m^3/s
Stream Discharge Equation
- Q = AV
- Q is stream discharge
- A is the cross-sectional area of the stream channel
- V is flow velocity (the avg of velocities indicated by the arrows)
Flow can be laminar or turbulent:
laminar: straight
turbulent: many different directions
Which type of flow is likely to be most effective at transporting sediment? Why?
Turbulent because it uproots sediment into the water flow
The amount of water in a river’s watershed increases:
downstream, with addition of tributaries
What is the thalweg?
the part of the stream that has the highest flow velocity, goes the long route, carves out the deepest part (erosion), is most insulated from friction from stream bed, it moves throughout the stream
What is the relationship b/w the water velocity and the depth?
Deepest goes fastest b/c protected from friction from stream bed
Materials are carried in different ways within a stream
Suspended load, bed load, dissolved load
What are the 3 types of stream channels and their shape?
- Straight (self-explanatory)
- Meandering (snaking)
- Braided (self-explanatory)
Braided stream type is associated with:
larger grain sizes and steeper slope, near headwater
Flooding is a
natural process in healthy streams
Why is there a delay between the rain event and the flood peak?
Floodwater comes from upstream and takes time to come downstream, farther the distance the water has to move, the longer the delay
Streams may develop a graded profile
headwaters tend to be the steepest slope then flattens out, every stream tries to achieve this
Headward erosion
erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, lengthening the stream channel.
Stream piracy
occurs when a stream or river drainage system or watershed is diverted from its own bed, and flows instead down the bed of a neighbouring stream.
Fluvial landscape evolution:
narrow V-shaped valley with enough time will turn into a floodplain
Fluvial systems adjust to changes in Base Level:
any stream with enough time reaches graded profile
Dams can cause problems
Creates artificial base level, now becomes new stream profile formed by sediment deposition
What other types of problems, upstream and downstream, can be caused by construction of dams?
Must consider what’s underneath the reservoir, if limestone and porous then mountain can give way and create a tidal wave and kill everyone downstream
Terrace
form when streams carve downward into their floodplains, leaving discontinuous remnants of older floodplain surfaces as step-like benches along the sides of the valley.
Alluvial fan:
usually dry = continental, deposits sediment in fan-like way
Delta:
sediment deposited when stream meets ocean and stops
Progradation
growth of a river delta farther out into the sea over time
Avulsion
basically switching channels b/c sediment deposit becomes high point and river goes around it
Drainage System Maintenance is important because:
Need to avoid: polluted runoff and anoxic dead zones