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The rain gages in the urban watershed below, which has a basin areaof 28 km2, measure the following cumulative precipitation during a 1-hour storm event: The basin is in an

arid environment where there is no baseflow. Themeasured hydrograph at the stream outlet resulting from the storm ismeasured to be: a) Compute the mean areal rainfall during the storm (in units of cm)using the Theissen polygon method. Note: You can simply re-usethe areal weights calculated previously. b) Using the trapezoidal method for integration, what is the totalstormflow runoff (in units of cm) for the storm? Plot the hydrograph. c) Generate the 1-hr unit hydrograph (i.e. corresponding to 1 cm ofrunoff) for this basin based on the hydrograph shown above and youranswer to part b). Your answer should be in the form of a tabulatedhydrograph (time and flow) and should have units of m3s-1/cm. d) Using your unit hydrograph and the superposition principleconstruct the predicted hydrograph for a 3 hour storm with aeffective cumulative precipitation (i.e. stormflow runoff) of 9 mm. Plothe predicted hydrograph. What is the predicted peak flow for thistorm and the time-to-peak?

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