Hydrologic and Biotic Effects of Grazing vs. Non-grazing Near Grand Junction, Colorado

Abstract

The effect of grazing on the hydrology of salt-desert type rangeland has been studied near Grand Junction, Colorado for the past 14 years. Measurements of precipitation, runoff, erosion, and vegetation have been made in four pairs of watersheds. One of each pair has been grazed by cattle and sheep as is normal in the region, and the other has not been used since the beginning of the study. Measurements made 10 years apart show that all four grazed watersheds have had a slight increase in the amount of bare soil and rock and a decrease in ground cover; cover on ungrazed watersheds has remained essentially unchanged. Runoff in the ungrazed watersheds has been about 30 percent less than in the grazed watersheds and sediment yield has been about 45 percent less. The greatest change in each of the relationships occurred about 3 years after livestock were excluded from one watershed of each of the pairs. Preliminary studies indicate that within areas of similar physiography, runoff is directly related to the percentage of bare soil present on a watershed.