22, CIRCULAR 925, U. 8S. DEPARTMENT OF AGRICULTURE 
Mean precipitation at Modena for the period of record (1901-47) 
was 10.83 inches; at Deseret (1900-47) it was 7.84 inches. Means at 
both places—10.85 and 7.10 inches, respectively—for the period of 
study, 1934-47, compare rather closely with these figures. It is there- 
fore reasonable to believe that mean precipitation at the Desert Experi- 
mental Range during the period of study is fairly representative of what 
might be expected over a longer period of time. Fluctuations in yearly 
amounts at all three locations followed a similar pattern, with few 
exceptions, during the period 1934-47. Fluctuations at Modena and 
Deseret were also similar in pattern during the longer period of record. 
Rainfall data at the experimental range headquarters have been 
tabulated by 3-month periods for a 12-month rainfall year, from 
October 1 to September 30, because plant growth on the winter range 
begins about March or April and almost all growth is completed before 
the end of September (table 6). Precipitation for October to December 
is considered as contributing to the next year’s growth. On this basis 
mean annual precipitation at the Desert Experimental Range was 6.69 
inches for the period of the study, with a minimum of 3.78 inches in 
1941-42 and a maximum of 11.10 inches in 1946-47. Precipitation 
was above average in only 5 of the 13 years. 
TABLE 6.—Seasonal and yearly precipitation (inches) at Desert 
Experimental Range headquarters, October 1 to September 30, 1934-47 
Period | Oct.—Dec. | Jan._March | Apr—June | July-Sept. Total 
034-952 | 0.59 0.87 2.42 4.00 7.88 
1935 36-0 | i 1.62 21 4.20 6.34 
1986-37. 1.64 | 87 1.05 | 2.28 5.84 
087-3855 =| 1.08 1.52 3.41 | 2.81. 8.82 
493823002 = | 2.05 86 2 AZ | 1.28 6.66 
1939-40. = 2 = | 98 1.49 53 1.62 4.62 
7040-41-65 = | 1.18 1.51 | 3.29 1.74 7.72 
‘Cue as 2.15 32 | 50 81 3.78 
1049-43 97 1.02 1.27 1.12 4.38 
gua 44 | 2.62 | 86 2.45 26 6.19 
(OM=45 2 e | 1.14 | 1.49 2.15 | 3.75 8.53 
1945-46... ____| 1.06 | 29 1.47 | 2.35 5.17 
1046-47 | 6.74 | 08 | 2.78 | 1.50 11.10 
fee 1.73 98 | 1.85 2.13 6.69 
Seasonal precipitation fluctuated widely. In general, its pattern and 
seasonal distribution showed little consistency. Less than one-fourth 
inch of precipitation occurred in many individual months, and less than 
one-half inch in several of the 3-month periods. Precipitation for the 
October to December period varied from 0.31 inch to 6.74 inches. 
Precipitation for the January—March period averaged only 0.98 inch. 
This was consistently a dry period. 
Precipitation for the two growing periods, April to June and July to 
September, was relatively high, averaging about 2.00 inches for each 
period. During the latter period rainfall was cyclic in character. It 
was relatively high during the first 4 years, low from 1939 to 1944, and 
relatively high again in the next 2 years. 
