A comprehensive study of the hydrologic and biotic characteristics of small drainage basins on the Colorado Plateau and the effect of grazing on these characteristics vas begun in 1953. This report presents data obtained during the first 5 years of the proposed 20-year study.
Periodic observations were made at permanent transects in 8 paired fenced and unfenced watersheds to characterize plant and ground cover, determine degree of use by livestock and measure changes in watershed cover. Results after 5 years of study indicate that changes in watershed cover have been relatively small on both grazed and ungrazed areas. Changes that did take place were mainly on shale and mixed type .soil. Ground-cover index on mixed type soil was significantly higher, 4 percent, on ungrazed ,areas than on grazed areas at the end of 5 years.
Plot records were obtained using the Rocky Mountain Infiltrameter at 12 plots in each of the 8 study watersheds to determine the effect of livestock exclusion on infiltration and sheet erosion. Infiltration rates for the last 20 minutes of both the wet .and dry runs were significantly higher in 1958 than they were 5 years before, but this difference was not associated with treatment because rates on both grazed and ungrazed plots increased about .the same amount. The initial water-absorbing capacity increased significantly on ungrazed plots. No change in erosion rates was observed.
Rainfall was variable and below normal during 4 of the first 5 years of study. Runoff was produced mainly by thunderstorms during the summer months and was characterized by high rates of flow for short periods. Comparison of runoff in grazed and ungrazed watersheds indicates a change in the relation between precipitation and runoff because of exclusion of livestock. More sediment per unit area was produced during the 5 years of study from grazed .areas than from ungrazed areas.
No definite trend in small mammal population on grazed and ungrazed water- sheds has yet been determined. Results of preliminary studies on rabbit population indicates that rabbits prefer to inhabit ungrazed areas, but populations were judged to be not high in any area.
Additional publication details
USGS Numbered Series
Hydrologic and biotic characteristics of grazed and ungrazed and watersheds of the Badger Wash basin in western Colorado, 1953-58
Water Supply Paper
U. S. Govt. Print. Off.,
v, 73 p. :illus., maps (1 fold. in pocket) ;24 cm.