The following from the same author of the minimum flow of streams in cubic feet per second, per each square mile of water-shed:
From 1 square mile .083 From 10 square miles .1 From 25 square miles .11 From 50 square miles .14 From 100 square miles .18 From 250 square miles .25 From 500 square miles .40 From 1,000 square miles .35 From 1,500 square miles .38 From 2,000 square miles .41
From the different surfaces, its ratio of the annual rain, including floods and flow of springs, is approximately as follows:
PER CENT. From mountain slopes or steep rocky hills, 80 to 90 From wooded swamp lands, 60 to 80 From undulating pasture and woodland, 50 to 70 From flat cultivated land and prairie, 45 to 60
------------------+----+----+----+----+----+-----+ |JAN.|FEB.|MAR.|APR.|MAY.|JUNE.| ------------------+----+----+----+----+----+-----+ Mean ratio--inches|.30 |.35 |.50 |.80 |1.45|1.70 | ==================+====+====+====+====+====+=====+
------------------+-----+----+-----+----+----+---- |JULY.|AUG.|SEPT.|OCT.|NOV.|DEC. ------------------+-----+----+-----+----+----+---- Mean ratio--inches|1.85 |2.00|1.45 |.75 |.50 |.35 ==================+=====+====+=====+====+====+====
AVERAGE AVAILABLE RAIN-FALL FOR STORAGE PURPOSES.
------------------------+----+----+----+------+----+-----+ |JAN.|FEB.|MAR.|APRIL.|MAY.|JUNE.| +----+----+----+------+----+-----+ Gain by rain--inches |2.00|2.21|2.40| 2.93 |3.47|2.88 | Loss by evaporation--in.| .60| .70|1.00| 1.60 |2.90|3.40 | +----+----+----+------+----+-----+ Difference--Gain inches |1.40|1.51|1.40| 1.33 | .57| -- | Difference--Loss inches | -- | -- | -- | -- | -- | .52 | ========================+====+====+====+======+====+=====+
------------------------+-----+----+-----+----+----+----+------ |JULY.|AUG.|SEPT.|OCT.|NOV.|DEC.|TOTAL. +-----+----+-----+----+----+----+------ Gain by rain--inches |2.99 |3.00|2.67 |2.53|2.48|2.24| 32. Loss by evaporation--in.|3.70 |4.00|2.90 |1.50|1.00| .70| 24. +-----+----+-----+----+----+----+------ Difference--Gain inches | -- | -- | -- |1.03|1.48|1.54| 8. Difference--Loss inches | .71 | .80| .23 | -- | -- | -- | -- ========================+=====+====+=====+====+====+====+======
SUMMARY OF FLOW OF RAIN-FALL IN CU. FT. PER MINUTE PER SQUARE MILE.--(_From Fanning._)