As the months are of varying length it is necessary to use three or four factors to convert the average discharge for the month in secondfeet into the total in acre-feet. One second-foot flowing for twentyfour hours is equivalent to 86,400 cubic feet. Since there are 43,560 square feet in an acre there will be the same number of cubic feet in an acre-foot. Dividing, it is found that 1 second-foot for twenty-four hours very nearly equals 2 acre-feet, or, in exact figures, 1.983471 acrefeet. This multiplied by the number of days in the month will give the total monthly discharge in acre-feet. This quantity, therefore, must be multiplied by 28 for the month of February, or 29 for that month in leap year, and by 30 or 31 for the other months.

For the month of February when it has 28 days the factor to be used is 55.537188. For convenience in computation this factor multiplied from 1 to 9 is given in the following table:

When February has 29 days the factor to be used is 57.520659. This when multiplied from 1 to 9 gives the following:

For the months containing 30 days, viz, April, June, September, and November, the factor to be used is 59.504130. This, when multiplied by the unit figures, gives the following results:

For the months containing 31 days, viz, January, March, May, July, August, October, and December, the factor to be used is 61.487601. This, when multiplied by the unit figures, gives the following results:

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Table for converting second-feet into acre-feet per month of twenty-eight days.

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Table for converting second-feet into acre-feet per month of twenty-nine days.

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Table for converting second-feet into acre-feet per month of thirty days.

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Table for converting second-feet into acre-feet per month of thirty-one days.

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