Chapter 13 Flashcards
What is the proportion of liquid (not frozen) freshwater on Earth expressed as a percentage of all water on Earth?
Approximately 1% of the Earth’s water is liquid fresh water.
What percentage of that fresh water is groundwater?
Approximately 30% of the Earth’s fresh water is groundwater.
How do B.C.’s coastal streams differ from most of the rest of the streams in Canada in terms of their annual flow patterns? Why?
In coastal regions of B.C. the highest levels of precipitation are in the winter, and large parts of most drainage basins are not frozen solid. As a result stream discharges tend to be greatest in the winter.
Why do most serious floods in Canada happen in late May, June, or early July?
In most parts of Canada winter precipitation is locked up in snow until the melt season begins, and depending on the year and the location that happens in late spring or early summer. If the thaw is delayed because of a cold spring, and then happens very quickly, flooding is likely. Some regions also receive heavy rainfall during this period of the year.
There is a 65-year record of peak annual discharges on the Ashnola River near Princeton, B.C. During this time, the second highest discharge was 175 m3/s. Based on this information, what is the recurrence interval (Ri) for that discharge level, and what is the probability that there will be a similar peak discharge next year?
Ri = (n+1) ÷ r (where n is the length of the record) and r is the rank of the flood in question. In the Ashnola River case Ri = (65+1) ÷ 2 = 33. The probability of such a flood next year is 1/Ri, or 1/33 which is 0.03 or 3%.
