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.~ w w Rangeland Management t..:. c.;) Vegetation, including canopy cover, ground cover, and litter, reduces upland soil loss by protecting soil from direct raindrop impact and by reducing surface runoff velocities. Increased sediment production from saline soils will cause increases in salinity contributions to the Colorado River. Vegetation also intercepts rainfall and enhances soil inftltration properties, thus reducing runoff volume and erosion on hillsides and in stream channels. Riparian vegetation traps sediment from the uplands, reduces stream bank erosion, and provides stability for stream banks. Establishment of riparian vegetation in degraded areas reduces the need for continued structural control and lowers future maintenance costs. Management of vegetation cover and resultant decreases in sediment yield are accomplished through grazing, land treatment, and structural techniques. Grazing Techniques. Livestock grazing affects vegetation by influencing species composition, vigor, production, and cover densities. Proper livestock grazing techniques can increase ground cover in most areas. Quantitative relationships between livestock grazing systems and sediment production or salinity have not been fully researched and developed. Thus, it is difficult to accurately predict the effects of different livestock grazing plans on resulting runoff, erosion, and salinity. However, rangeland condition is carefully monitored to evaluate the extent to which management objectives are achieved. Land Treatment Techniques. Land treatment techniques must be carefully tailored to the site, with topography and soil characteristics dictating treatment types and design. For example, some range sites such as large areas of pinyon-juniper or big sagebrush lack sufficient understory vegetation to provide appropriate ground cover. Livestock grazing has very little influence on these sites and, consequently, it is impossible to improve ground cover through grazing management. These sites may have high potential for increasing ground cover and reducing runoff with mechanical or prescribed bum treatments. Mechanical land treatments involve soil tillage techniques such as contour furrowing, ripping, and pitting. Tillage is generally applied to increase infiltration volumes. This may be accomplished by increasing inftltration capacities or depression storage (the time available for infIltration) or both. When successful, runoff and erosion can be reduced. Salinity benefits will be proportional to the amount of salt in the controlled runoff and sediment. If improved soil moisture regimes improve vegetation cover, benefits derived from land treatments may be sustained indefinitely, given compatible subsequent land-use management. If improved cover is not achieved or maintained, benefits from land treatments may be short-lived. Structural Techniques. Common structural techniques used in managing runoff, sediment, and salt yields include rangeland dikes, retention plugs, retention and detention reservoirs, and gully plugs. Retention and detention structures trap runoff and sediment volumes in accordance with their design capacities. Generally, total runoff retention is required for a structure to effectively control salinity. Gully plugs usually have small retention capacities, but provide salt and sediment control by reducing erosion in active gully systems. In addition to effectively controlling downstream impacts associated with runoff, erosion, and salinity processes, retention/detention structures may provide local benefits. Reservoirs provide water for livestock and wildlife. Even after fIlling with sediment, they may provide a riparian-like habitat. Gully plugs, when properly located, can cause 12