Impact of cattle grazing on the surface water quality of a Colorado Front Range stream

Abstract

The purpose of this study was to quantify the impact and evaluate the local and immediate downstream pollution potential of range cattle grazing with free stream access. Emphasis was placed on suspended solids, ammonia-nitrogen, nitrate-nitrogen, orthophosphate, fecal coliform and fecal streptococci concentrations. Samples were collected at four sites along a 2.6 km section of Trout Creek, the only perennial stream within the Manitou Experimental Forest. The study was broken down into eight periods covering the two year period 1977-1978; two included 150 cows in the lower pasture, two involved grazing by 40 cows in an adjacent pasture while four periods involved no grazing in either pasture. The findings of this study indicate that only fecal coliform and fecal streptococci concentrations reflected a cattle grazing impact. Ammonia-nitrogen and nitrate-nitrogen concentrations suggest a grazing impact while orthophosphate concentrations appeared to be independent of cattle grazing. During most of the study the suspended solids analyses were confounded by an area of breached beaver darns. Cattle location and defecation trends help to explain the low concentrations of the parameters involved. In many instances the contribution by grazing cattle was minor in comparison to background concentrations measured at upstream sites.

Citation

Johnson, Steven R. 1978. Impact of cattle grazing on the surface water quality of a Colorado Front Range stream. Fort Collins, CO: Colorado State University. 115 p. Thesis.