26 



T, Lyttleton Lyon and James A. Bizzell 



years passed thru the unplanted soil. Occasionally the drainage exceeds 

 the precipitation. This occurs, with one exception only (in November, 

 1913), in the period included in that part of the year beginning with 

 December and ending with April. In 1912 there was a very heavy flow 

 in September, but it did not exceed the rainfall, which was excessive 

 for that month and also was large for the two preceding months. 

 Ordinarily a large flow takes place in December or January accompanying 

 a temporary thawing of the frozen soil. February is likely to see a small 

 amount of drainage, the soil being deeply frozen at that time. This is 



aao- 



Dra/nage 



1 I I I I ■] f I M I I I M 



J I I I I I I 111 I I I I I I I I I I M.J. I I J , I III !,'<U-.|:rl'-J 



iiu), ij'kk^!J*(5 





/9/0 -// 



/9//-/a 



t9/a-/3 



/9/3~ /-^ 



Fig. 5. 



RELATION OF DRAINAGE TO RAINFALL BY MONTHS FOR THE UNPLANTED AND 



LIMED TANK 8 



usually followed by the largest flow of the year in March or April, at 

 which time the melted snow comes thru the soil. 



Months of large rainfall are not always months of large drainage flow. 

 This may be accounted for in the summer, when the temperatures are 

 high and the humidity is low, by supposing a large evaporation from 

 the surface of the soil. There appears, however, to be an accumulation 

 of moisture in the soil for a considerable period and then a rapid discharge. 

 In winter this is Ukely to be coincident with a thaw, and is then more 

 pronounced than at other times. The heavy discharges in December, 

 frequently exceeding the rainfall, are not usually due to an accumulation 



26 



