Plate 12.—If the interpreter has discovered a basin type in his photos he turns to this page 
and verifies this determination by first checking the recognition features. Then he gets very specific 
information on what to expect in his photos and how to deduce what activities are taking place. 
COLORADO PLATEAU 
BASIN TYPE 
RECOGNITION FEATURES 
1. Vide valleys, nearly level, with gently sloping valley 
sides. 
2. Deep gully erosion frequent. 
3. Vegetation usually low brush or sparse weeds, occasion 
ally covered by open woodland, frequently barren. 
VARIATIONS 
1. Upper basins under scarps of plateaus, 6,000 - 7,000 ft. 
2. Lower valleys of rivers, 5,000 - 6,000 ft. 
3. Deserts in lowest valleys, 4,000 - 5,000 ft. 
ASSOCIATIONS 
Climate - semi-desert. Light scattered electrical storms 
from July through September with occasional heavy downpours. 
Dust storms in spring. Light snow does not remain after 
winter storms. Annual precipitation 5" - 15". 
Soils - mostly alkaline clays. Composed of weathered sand 
stone, shale and limestone materials washed down from plat 
eaus, forming deep sandy clay deposits. Alkali excessive 
in basins without good drainage, making soils infertile and 
water bad. Much coarse alluvium deposited in dry washes. 
Sheet and gully erosion frequently severe. Soils very 
slick when wet. Clays used to make adobe bricks. 
water Supply - dependent on deep wells, reservoirs, earth 
tanks and cisterns. Minor drainage channels are dry washes 
during most of year, fcith water flowing only after summer 
storms. Rivers usually aggraded with silt and coarse alluvium. 
Vegetation - cover of sagebrush frequently found in upper 
basins. Open woodlands of plnon-juniper occasionally found 
on edges of upper basins. Lower basins have bitterbrush and 
shadscale brush on alaaline areas, and a sparse cover of 
weeds elsewhere. Used as winter range for cattle and sheep. 
Some areas being reseeded with range grasses or unirrigated 
crops. Frequently large areas are barren. 
Culture - agriculture usually irrigated. Some dry farming, 
in upper basins, raising small grains and beans. Some large 
commercial irrigation, depending on reservoirs. Large set 
tlements occur at road and rail junctions, or in irrigated 
valleys. Many fcanch headquarters and small towns also found. 
Some small wood-using industries depending on plateaus for 
raw material. Some oil wells, natural gas wells and pipe 
lines. Uranium processing plants springing up. 
Transportation - Main paved roads and railroads use this 
terrain type principally. Cattle shipping points found 
along rail lines. Vide "dips" required in roads to allow 
passage of flash floods. Flash floods disrupt travel on 
minor roads in summer. 
■ ü f 
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MIMING 
Fig. 2.11 The basin type. This basin at 6,500 ft. elev. 
is filled with weathered rock waste from receding escarp 
ments around it, which ranges from adobe clay on the flats 
to coarse alluvium in the dry washes. The basin is irrig 
ated by trapping summer rainfall behind a dam at the left, 
but it can only supply part of the water needs, and dry- 
farming is being attempted at the right. In the lower 
center is Zuni Pueblo made up of adobe clay houses. The 
Zunis are a progressive tribe and have been peaceful agri 
culturalists for generations. The basins are the favored 
sites for road locations in much of this region. New 
Mexico. December 1948. 
GVII-96 PHOTOGRAMMETRIC ENGINEERING