You take two very careful flow measurements in the River, one mile apart from ea

Question

You take two very careful flow measurements in the River, one mile apart from each other. At the upstream cross section you measure a discharge of 991 cubic feet per second (cfs). At the downstream point you measure 981 cfs. Assume that your measurements are representative of the whole river as well as the whole year. If the River loses 10 ft^3 of water every second over each mile of flow distance, how much water seeps through its bed into the aquifer over the full 96 mile length that flows over the Basin over an entire year?

Explanation / Answer

Over each mile of distance, the river loses 10 ft3 of water per second.

Hence over 96 miles of distance, the river loses 96×10 = 960 ft3 of water per second (which seeps into the aquifier).

A standard year can be taken to be 365 days, or, to be more standard, (365×3+366×1)/4 = 365.25 days, if one averages out every fourth leap year, which has 366 days.

Each day contains 24 hours; each hour contains 60 minutes, and each minute contains 60 seconds; hence each day contains 24×60×60 = 86400 seconds

For a year with n days (where n = 365, 365.25, or 366), the number of seconds is 86400×n

For n = 365.25, hence, the amount of water that seeps through the river-bed into the aquifier is 86400×365.25×960 = 31557600×960 = 30295296000 ft3

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