6 BTJLLETIX 498, U. S. DEPARTMENT OF AGRICULTURE. 
Table II. — Monthly and annual precipitation at Grass Valley and Moro, Oreg., showing 
the average, maximum, and minimum for each month, from 1905 to 1915, inclusive. 
[Precipitation data (in inches): Previous to December, 1909, from the Oregon-Washington Railroad & 
Navigation Co., Grass Valley, Oreg.; since December, 1909, from the substation records. T=traee.] 
Year. Jan. 
Feb. 
Mar. 
Apr. 
Mav. 
June. 
July. 
Aug. 
Sept. 
Oct. 
Nov. 
Dec. 
An- 
nual. 
1905 
0.76 
0.20 
.85 
.48 
..02 
1.03 
1.47 
.46 
1.36 
.23 
1.16 
2.31 
0.05 
1.65 
1.60 
.68 
.68 
.63 
.25 
.69 
.76 
.11 
1.27 
0.03 
.10 
1.06 
.11 
.10 
.66 
.35 
.78 
.58 
2.06 
.65 
1.70 
1.05 
.90 
1.41 
.49 
1.25 
1.05 
1.33 
2.27 
.76 
2.06 
1.30 
1.S5 
.89 
.37 
.99 
.89 
.64 
.42 
1.39 
.66 
.36 
0.36 
T 
.30 
.22 
.10 
T 
.00 
.02 
.06 
.08 
.57 
T 
.34 
.71 
.34 
.02 
.00 
T 
.74 
.05 
T 
.05 
0.75 
.35 
.50 
.12 
.45 
.20 
4.03 
.21 
.49 
1.05 
1.14 
1.36 
T 
.20 
1.11 
.87 
.70 
.33 
.78 
1.87 
1.48 
.23 
0.85 
2.59 
1.46 
1.12 
3.34 
2.76 
.30 
1.30 
1.45 
.88 
2.89 
1.35 
2.22 
2.68 
1.63 
1.14 
.88 
.61 
2.12 
1.69 
.88 
1.61 
S. 71 
1906 
1.00 
12.00 
1907 
190S 
1909 
1910 
2.65 
55 
2.56 
95 
13.43 
7.68 
11.77 
10.39 
1911 
1912 
1913 
1914 
LIS 
3.58 
1.33 
2.20 
9.20 
13.33 
12.17 
11.32 
1915 
1.75 
14.89 
Average . . 
..." 1.68 
.87 
2.31 
.02 
.76 
1.65 
.05 
.59 
2.06 
.03 
1.30 
2.27 
.49 
.89 
1.S5 
.37 
.16 
.57 
.00 
.20 
.74 
.00 
.84 
4.03 
.12 
.81 
1.87 
T 
1.72 
3.34 
.30 
1.53 
2.58 
.61 
11.35 
Maximum 
Minimum 
3.58 
.55 
14.86 
7.68 
The distribution of the precipitation usually is favorable for grow- 
ing cereals, nearly all of the rain falling during the months from 
Fkj, 4.— Experimental plats at the Moro substation in the spring of 1916, showing the run-off during the 
melting of a heavy covering of snow. 
September to June. July and August are practically rainless. In 
some years there is considerable run-off in the winter or early spring 
(fig. 4). Soil samples taken to a depth of 6 feet on 20 plats in May, 
1913, had an average of only 1 per cent more moisture than samples 
taken on the same plats in November, 1912, though the precipitation 
during the interval measured 5.5 inches. From September 1, 1914, 
to February 28, 1915, the precipitation was 8.35 inches, but this 
penetrated stubble ground to a depth of less than 2 feet. The rains 
