Additional unit conversion problems


1. A rainstorm delivers 3.4 inches of rain to a 1.2 square mile watershed.

Half of the watershed is forested, with 90% infiltration and 10% surface runoff.
The other half is a commercial district with 40% infiltration and 60% runoff.

What is the total volume (in cubic feet) of runoff?

If a stream draining this watershed discharges storm flow at an average of 230 cfs, how many hours will it take for all the stormflow to exit the watershed?


2. A new dam is constructed to impound a reservoir that, when full, will be 1.3 square miles in area and will average 22 feet deep.

A single tributary will provide inflow to the reservoir at an average discharge of 26 cfs.

During the time that the reservoir fills with water, outflow from the dam will be controlled at 8 cfs to provide flow to downstream fisheries.

Also during the filling period, it is estimated that 0.1 inches of lake water will percolate into the groundwater every day over the entire 1.3 square mile area of the lake.

Assuming no other inflows or outflows (no direct precipitation, evaporation, etc.), how long will it take for the lake to fill?


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