A storm occurs over a 27-square-mile watershed. The measured rainfall and stream flow are shown in the following tables. Derive the unit hydrograph from the data. Is the result a 1-hr, 2-hr, or 3-hr unit hydrograph? What fraction of the precipitation appears as runoff? Assume the groundwater contribution is linear from 100 cfs (at t = 0600) to 160 cfs (at t = 0200).

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Time 5 to 6 A.M. 6 to 7 A.M. 7 to 8 A.M. 8 to 9 A.M. 9 to 10 A.M. Rainfall (in. 0 08 060.60.1 Time (hrs) 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200 2400 0200 Q (efs 10 100 1,200 2,000 1,600 1,270 1,000 700 500 300 180 160