Hydrologic responses of a montane riparian ecosystem following cattle use

Riparian areas link streams with their terrestrial catchments and decrease water pollution by trapping sediments from upland sources before they reach streams or lakes. Livestock grazing in riparian areas is a controversial p ractice. If not properly managed, cattle can cause degradation to both the riparian zone and adjacent water body. Vegetative, soil microtopographical, microchannel and hydrograph parameters were measured in a montane riparian community in northern Colorado to quantify the effects of cattle on overla nd flow and runoff characteristics. Treatments were cattle grazing plus tra mpling. cattle trampling, mowing, and a control. Water was applied to plots (3 m x 10 in) at a rate of 100 mm hr(-1) using a rainfall simulator. Concu rrently, overland flow was introduced at the upper end of the plots at an e quivalent rate of 25 mm hr(-1). A high intensity-short duration grazing tre atment was used for the cattle-treated plots. Reduction in vegetation stem density and aboveground biomass by cattle decreased microchannel sinuosity and drainage density. Cattle-treated plots had greater now velocities and d epths in microchannels compared with mowed and control plots. Reduced stem density and aboveground biomass by grazing left fewer obstacles to divert f lows, which decreased microchannel sinuosity and drainage density. Flows we re concentrated into fewer microchannels with deeper flows. Microchannel ch aracteristics were not significant factors affecting total runoff. Stem den sity and rainfall intensity were the most important factors in predicting r unoff characteristics and total runoff. Results from this study have improv ed our understanding of now and runoff processes following cattle use of a riparian ecosystem.