68 



BULLETIISr 71, U. S. DEPARTMENT OF AGRICULTURE. 



In order to obtain the relation between rainfall and run-off for lands of this 

 section, rain gauges were installed on a number of districts in June, 1909, and a 

 careful log of pumping-plant operation has since been kept. The capacities 

 of the vai'ious pumps were obtained by careful ratings. The three areas (Nos. 

 1, 2, and 8) on which these records were kept have already been described in 

 detail. An examination of the descriptions will show that these districts vary 

 widely in natural characteristics and in the natui'e of the improvements. In 

 applying the results obtained to any other sections these local conditions should 

 be considered. The daily records for the entire period will not be included 

 here ; only the records of heavy storms will be given, these latter being all that 

 are required to determine the proper run-off coefficient. The run-off results vary 

 so widely on the different tracts that they will be discussed separately, and the 

 proper rate of run-off to be provided for will be determined in a preliminary 

 way. It is to be understood, however, that these conclusions are not final and 

 that records of rainfall and run-off extending over longer periods may lead to 

 different ones. 



The following table for area No. 2 gives the rainfall and run-off for the eight 

 heaviest storms that occurred during the period, June, 1909, to May, 1912. 

 The stages of water in the reservoirs above or.below the general ground surface 

 are given as of 8 a. m. and 8 p. m., these being the usual hours at which 

 the plant was started and stopped when operating in daytime ; of course during 

 the heaviest storms considerable pumpingjwas done at night. The condition of 

 the soil at the time of the storm is also noted. 



Rainf all, water pumped, and reservoir stages due to heaviest storms occurring on 

 area No. 2, June, 1909, to May, 1912. 



[Reservoir capacity, 0.45 inch. Pumping capacity, 1.11 inches.] 







Water 



Stage of water in 



No. of 

 hours 





Date. 



Rain- 

 fall. 



pump- 

 ed. 



reservoir above 

 {+) or below (— ) 



land 

 flood- 

 ed. 



Condition of soil before storm. 







general surface. 







Indies. 



Inches. 



8 a. m. 



8 p. m. 







1909. 



Feet. 



Feet. 





June 1 



O.bo 



0.00 











2 



4.20 



.71 











3 



.00 



1.10 



■ Not recorded. 





Well drained, and one-third in cultivation. 



4 



.39 



.40 











5 



.00 



.22 











Aug. 9 



1.14 



.00 



-0.1 



+0.1 







10 



1.68 



.80 



+0.2 



—1.0 







11 



2.80 



.90 



-2.0 



0.0 



18 



Do. 



12 



.02 



.80 



-0.3 



-2.0 







13 



.13 



.40 



0.0 



-2.5 







Sept. 19 



.65 



.00 



-0.3 



-0.2 







20 



3.30 



.33 



-0.1 



+0.3 







21 



.00 



.47 



-hO.6 



+0.3 







22 



.00 



.72 



-1-0.6 



+0.1 



54 



Do. 



23 



.00 



.45 



-0.4 



-0.6 







24 



.00 



.^ 



+ 0.3 



-0.2 







Dec. 11 



2.80 



.00 



-1.0 



0.0 







12 



.15 



.63 



+0.4 



+0.2 







13 



.00 



.62 



+0.2 



-0.2 



40 



Saturated, and one-third in cultivation. 



14 



.00 



.42 



+0.3 



-1.0 







15 



.00 



.37 



0.0 



-2.6 







1910. 















July 1 



.50 



.15 



-1.6 



-2.7 







2 



1.82 



.23 



-2.0 



-1.6 







3 



3.40 



.54 



-0.6 



-0.9 







4 



.36 



.77 



+0.1 



+0.1 



36 



Well drained, and two-thirds in cultivation. 



5 



.05 



1.06 



+0.1 



0.0 







6 



.00 



.70 



-0.1 



-0.7 







7 



.00 



.41 



-1.3 



-2.0 







