Nov. s, 1917 
Run-off from Drained Prairie Lands 
267 
ACTUAL RATES OE RUN-OFF DUE TO HEAVY STORMS 
In the foregoing tables of rainfall and run-off the figures under the 
columns headed “Run-off,” with the exception of those shown for the 
New Orleans Land Company tract, are in fact the amounts pumped 
rather than the run-off of the water from the surface into the main 
drainage channels. In the case of the tract excepted, the water dis¬ 
charges by gravity as fast as it enters the main outfall channel. For 
almost the entire period covered by the record of each plant, an hourly 
reading has been made of the stage of water in the main reservoir canal 
during the operation of the pumping plant. The amounts of water stored 
in the main drainage channels at the different levels have also been calcu¬ 
lated. By this means the amounts pumped per day during the heavy 
storms have been so adjusted for a number of typical storms on each 
district that the final results represent approximately the quantity of 
water which would have been removed had the pumps taken the water 
as fast as it entered the main reservoir channels; in other words, these 
results represent approximately the true run-off for the storms selected. 
With the exception of a very few heavy storms, only those were selected 
which occurred when the land in the district was saturated, or at least 
fairly wet. 
Table XI gives the dates, rainfall, and revised run-off for these selected 
storms. In the columns headed “Rainfall” are indicated by the words 
“Moist,” “Dry,” etc., the condition of the land at the beginning of the 
storm periods. While the run-off is given as for consecutive dates after 
the beginning of pumping, this is not strictly correct, as the run-off was 
computed for 24-hour periods following the starting of the pumps, regard¬ 
less of the calendar dates. Following each table are shown the number 
of heavy storms occurring when the land was dry and the number occur¬ 
ring when the land was wet. These figures include all of the 2- and 4-inch 
storms that occurred during the entire period of observation. 
Tabus XI .—Typical heavy storms and probable actual run-off of all districts 
SMITHFORT PLANTING COMPANY TRACT a 
Rainfall. 
Run-off. 
Date. 
Rainfall. 
Inches . 
Inches. 
19 * 3 * 
Inches. 
1. 68 
O. 89 
Sept. 12. 
O. 80 
2. 80 
I- *5 
13. 
3. OO 
Moist. 
. 4 * 
14. 
• IS 
. 11 
ic. 
Wet, 
26. 
.42 
27. 
2. 80 
1. 02 
28. 
Wet. 
2. 02 
•97 
29. 
Dry. 
•So 
. 02 
1914. 
3. 00 
1. 02 
Feb. 27. 
2.00 
0 
Moist. 
.48 
28. 
Wet. 
•03 
Mar. 1. 
Date. 
Run-off. 
Aug. 
Apr, 
Nov. 
1909. 
10. 
11. 
12. 
13 * 
1911, 
25 - 
26. 
27. 
28. 
27. 
28. 
29. 
Inches. 
I. 27 
I. 18 
•03 
I. 20 
•63 
•13 
I. IO 
•74 
a From June, 1909, to December, 1915, of all of the storms of over 2 inches, 8 occurred on dry land and 21 
on wet land; of those of over 4 inches, 3 occurred on dry land and 1 on wet land. 
