At 11:57 pm on March 12, 1928, the two-year-old St Francis dam on the outskirts of Los Angeles failed catastrophically and the dam emptied. The resulting flood was one of the worst US civil engineering disasters of the 20th century, claiming over 400 lives. The volume of water discharging from the dam, in acrefeet per minute, with time in minutes after midnight on March 13, is in Figure 5.57.
(a) How long did it take to empty the dam?
(b) What was the maximum discharge rate and when did it occur?
(c) How much water was discharged in total?
(d) How long did it take for the dam to be half-empty?

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discharge rate (acre-feet per minute) 1800 1600 1400 1200 1000 800 600 400 200 -10 0 10 20 30 40 50 60 Figure 5.57 70 minutes past midnight