CEREAL EXPERIMENTS AT CHICO, CALIF. 6 
TOPOGRAPHY. 
The valley lies in a troughlike depression which is believed once to 
have been an arm of the sea and which later was filled to its present 
level by material transported by the streams from the inclosing 
mountain ranges. The result is a broad, flat valley, varying in 
width from onlv a few miles in the extreme north to about 40 miles 
at Sacramento." The wide portion of the valley begins a short dis- 
tance north of Chico. The altitude of the valley floor 1 ranges from a 
few feet above sea level at its mouth to about 500 feet in the north, 
with the Sierras on the east rising to elevations of 6,000 to 8,000 
feet and the Coast Range on the west to elevations of 2,000 feet in 
the south to 6,000 feet in the north. 
For the most part, the valley floor is quite level, although in 
several sections it is gently rolling to somewhat hilly. South of 
Chico the lands along certain portions of the Sacramento River are 
higher than those more distant from the river, due to the deposition 
of sediment during times of flood. 
SOIL. 
Many varieties of soil are found in the Sacramento Valley. While 
most of these are of sedimentary origin, a few are residual and yet 
others of miscellaneous origin. The alluvial soils comprise the most 
fertile and most highly developed lands of the valley. While there 
are large areas of these lands they are often interspersed by undiffer- 
entiated soil types. The alluvial soils usually are about 6 feet 
deep, 1 although both deeper and shallower strata occur. These soil 
types are underlain by undifferentiated material of varying structure. 
The adobe or clay soils, which are very heavy in character, comprise 
another large group, of which there are several large areas as well as 
numerous smaller ones. These soils usually are from 2 to 3 feet 
deep and generally are underlain by a clay or hardpan subsoil. 
The lighter, shallower soil types usually are found toward the outer 
edges of the valley and on the gentle foothill slopes. 
CLIMATE. 
Climatic conditions in the Sacramento Valley are marked by 
two distinct seasons. The wet, or rainy, season occurs in winter 
and the dry, or rainless, season in summer. 
In general, the rainfall increases gradually from south to north, 
though there are some exceptions, as noted later. It ranges from 
about 15 inches annually in the southern portion of the valley to 25 
inches at Red Bluff on the northern border. The greater part of 
this precipitation falls in the four coldest months, while the summer 
months are practicallv rainless. Snow rarely occurs except in the 
extreme northern portion, where it usually melts w T ithin a few hours, 
) or at the most in a few days, after it falls. Thunderstorms and 
hailstorms rarely occur. Rainstorms usually are gentle in character, 
although heavy rains sometimes occur. A rainstorm generally lasts 
two or three days. During especially wet seasons they may last for 
a week to 10 days. 
holmes, L. C, Nelson, J. W.,et al. Reconnaissance Soil Survey of the Sacramento Valley, California, 
U. S. Dept. Agr., Bur. Soils, Advance Sheets, Field Oper., 1913, 148 p., 1 fig., 3 pi., map. 1915. 
