110 BULLETIN 1233, U. S. DEPARTMENT OF AGRICULTURE. 



exist in the original tabulations of the data. A further reason for not 

 attempting any high decree of precision in the record is the realization 

 that the total precipitation can show only in the most general way the 

 amount of water available for plant growth, as this amount will 

 depend perhaps as much on soil properties as on water received. 



Table 35. — Monthly and annual precipitation at the control station, in inches. 



Year. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Doc. 



Total 

 annual 



Total 

 grow- 

 ing 

 season 1 



1910 



1911 



1912 



1913 



0.01 

 .06 

 .06 

 .95 



2.35 



0.44 



1.56 



1.12 



.99 



0.51. 

 1.67 



.60 



1.04 



"i.*66" 



.97 

 1.83 



1.32 



1.18 

 2.20 

 1.56 

 2.06 

 4. 01 

 3. 53 

 4.54 

 1.77 

 2.68 



2.56 



.93 

 2. 07 

 1.76 

 2.40 

 3.43 

 1.99 

 3.77 

 .52 

 .49 

 2.23 

 1.07 



1.89 

 1.21 

 4.04 

 3.91 

 4.05 

 3.09 

 1.83 



.79 

 3.70 



.87 

 1.S8 

 8.17 



4.47 

 5.42 

 4.62 

 2.18 

 6.76 

 2.12 

 4.72 

 1.50 

 3.13 

 4.16 

 2.63 

 4.70 



3.27 

 2.01 

 1.82 

 3.92 

 2.06 

 4.78 

 3.11 

 3.87 

 3.32 

 1.46 

 6.39 



1.01 

 1.44 

 1.17 

 3.32 



.23 

 2.18 



.48 

 1.66 



0.86 

 1.45 



1.59 

 1.06 

 1.9S 

 .70 

 .54 

 .26 



0..53 

 .61 

 .17 

 .32 

 .10 

 .37 

 .63 

 .25 



0.61 



1.13 



.22 



5.01 



17.34 

 19.69 

 19.61 

 26.52 



9.97 

 9.12 

 10.87 



11.12 



1914... 



12.95 



1915 



.40 

 .40 

 .18 



'l9."64" 



17. 21 



10.74 



1916 



1917 



191 s -; 



.40 

 .25 

 .96 



.03 



1.08 



.94 



9.82 



6.71 



3 11.42 



1919 



1.82 

 1.17 



.75 

 1.87 



.94 

 .27 



.24 

 .73 



'2i.*28" 



6. S3 



1920 



1921 



.74 

 1.27 



1.12 

 .32 



.39 



1.20 



1.86 

 7.22 



11.74 



















Mean . . 



.50 



.84 



1.12 



2.96 



1.98 



2.95 



3. 8* 



3.27 



1. 45 



1.11 



.42 



.99 



21.46 



10.57 



i Prior to 1918 growing-season totals are obtained by using one-third the total for September; thereafter 

 the actual amount September 1-10 is used. 



2 Based on 0.23 inch, January 1-20. 



3 Based on actual fall of 1.27 inches, September 1-10. 



The complete record for the control station, by months, is shown in 

 Table 35. In this, as in all the succeeding records, the total for the 

 growing season has been obtained by adding to the amounts for June, 

 July, and August one-third the total for September. In fact, the 

 greater part of the September precipitation, or at least considerably 

 more than one- third, belongs to the second decade; hence this compu- 

 tation is only an approximation to the truth. 



Perhaps the most important thing shown by this table is that nor- 

 mally almost one-half of the total precipitation occurs during the 

 growing season. In nine years the least amount in this 102-day 

 period has been approximately 7 and the greatest 13 inches. To the 

 7 inches falling in 1917 there may be added, for all practical purposes, 

 the 3.77 inches in May, which left the ground in a soaked condition up 

 to June 5, and which materially assisted in tiding over the marked 

 drought which followed that date. Notwithstanding this, however, 

 the soil moisture at the end of the growing season reached a lower point 

 than has been recorded in previous years, and it may safely be said 

 that with less than this amount in the growing season there would be 

 danger of drought conditions which might affect the composition of 

 established stands. Unfortunately there were no soil-moisture 

 measurements made in the dry summer of 1919. 



In brief, then, the summer precipitation is ordinarily quite adequate 

 to maintain t he soil of the most exposed sites at this elevation in very 

 good condition. The winter precipitation is very inadequate, either 

 bo protect the soi] from severe freezing or to store up moisture for 

 Late spring use, except on north slopes and under dense stands. 

 ProhaDrj t here is about as much v ater here, in the form of snow to be 

 melted in the spring, as the soil will hold within reach of the roots. 



