CHAPTER 19: SURFACE WATER

Water covers 71% of Earth’s surface and is the dominant agent governing environmental processes.

Bassano Dam – part of major irrigation system in central Alberta Which country has the most abundant resources of renewable fresh water? ?

Data from , drawing by Steven Earlewww.woldwater.org We have much less water than we think, and a majority of surface water in Canada drains to the Arctic, so is not actually available to most Canadians. Canada

Water Use In Canada most of our water use is for energy generation and industrial purposes.

The Hydrologic Cycle The Hydrologic Cycle is the transfer of water between the atmosphere, the ocean, lakes and streams and the crust (as groundwater)

Runoff enters channels that join other channels to form a drainage system

Drainage Systems A Stream is any flowing body of water following a channel A river is a large stream, although there is no specific size cutoff for a “river” A Drainage System is a network of channels The total area feeding water to a stream is the watershed

Stream ordering within a drainage system

Drainage Patterns What situation will lead to a radial pattern? What about a trellis?

Stream discharge Stream discharge is the volume of water passing a point in a specific amount of time (e.g., m3/s) Q is stream discharge (volume/time) A is the cross-sectional area of the stream channel (shown here in blue) V is flow velocity (the average of the velocities indicated by the arrows) Q = AV

Flow can be laminar or turbulent Which type of flow is likely to be most effective at transporting sediment? Why?

The amount of water in a river’s watershed increases downstream, with the addition of tributaries

Thalweg The thalweg is the part of the stream that has the highest flow velocity. What is the relationship between the water velocity and depth shown by these diagrams?

Materials are carried in different ways within a stream Suspended load - Bed load - Dissolved load What is meant by “dissolved load”?

Hjulstrom Diagram The Hjulstrom Diagram shows the relationship between sediment size and the water’s ability to erode and transport sediments For sand and larger sizes there is a positive relationship between erodability and velocity. For silt and smaller sizes this same relationship applies to deposition, but not to erosion. It takes much high water velocities to erode clay once it has been deposited. Why is clay so hard to erode?

There are three types of stream channels: straight, meandering, and braided Straight

Meandering

Cut-off meander bends form Oxbow Lakes

Braided

Flooding is a natural process in healthy streams Cedar Rapids, Iowa Flood Animation Red River in Manitoba

Normal discharge “Bank-full” “Flood-stage” Why is there a delay between the rain event and the flood peak?

Normal versus flood-stage

Streams may develop a graded profile What is meant by “graded profile”?

Stream Piracy

Fluvial landscape evolution

Fluvial systems adjust to changes in Base Level

Dams can cause problems What other types of problems – upstream and downstream – can be caused by the construction of dams?

Incised Channels and Terraces

Fluvial sediment builds Alluvial Fans and Deltas Death Valley, California Mississippi Delta, Louisiana

Delta Terminology

Mississippi Delta avulsion What does avulsion mean?

Water problems exist on a global scale Which factors lead to the likelihood that a country will face water stress?

Drainage System Maintenance We need to look after drainage systems to avoid: – polluted runoff

Drainage System Maintenance – … and anoxic dead zones

Label the fluvial processes and landforms

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