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<br /> <br />w <br />OJ <br />o <br />1-" <br /> <br />BLM administers 48 million acres of public lands in <br />the Colorado River Basin above Imperial Dam, 36 percent of <br />the Basin's total area. Approximately 8 million acres of <br />BLM-administered lands in the Basin contain saline soils. <br />Salt concentrations on BLM lands are highest in saline <br />geologic settings, usually marine shales, where annual <br />precipitation averages less than 12 inches. <br />Salts enter tributaries of the Colorado River from <br />surface runoff, erosion, and ground water flows (nonpoint <br />sources), and from point sources such as saline springs, <br />spoil piles at mines, and 011 and gas production sites. <br />Most salt contributions to the Colorado River occur from <br />nonpoint sources. <br />Nonpoint Source Control <br />Controlling salinity in surface runoff from rangelands <br />ls closely related to controlling soil erosion. Vegetation <br />cover is usually the most important management variable <br />influencing runoff and erosion rates on rangelands. <br />Vegetation management, either indirectly through the <br />design and implementation of livestock grazing plans, or <br />directly through vegetation manipulation is an important <br />erosion and salinity control technique. However, on the <br />n~,st highly saline rangelands, maximum potential cover is <br />often ton lo~ to provide meaningful control of surface <br />runoff aTld erosion. <br />Proper land use, including grazing systems that <br />incorporate increased .paver, appropriate seasons of use, <br />and stream protection as objectives, is the BL'I's preferred <br />method of achieving salinity control. <br />In situations where the watershed condition is so <br />severely degraded that recovery will be inefficient under <br />normal land management practices, mechanical land <br />treatments and structural alternatives may be the most <br />f.->ffe('1 i\"p s::J.linity ('nntrol techniquE'S. MechaniC'al lRnn <br />treatments involve soil tillage techniques such as contour <br />furrowing, ripping, and pitting, Common structural <br />techniques include rangeland dikes, retention plugs, <br />retention and detention reservoirs, and gully plugs. <br />Point Source Control <br />Many saline water point sources exist on public lands <br />in the form of either wells or springs, Several wells have <br />been plugged, and other flowing wells will be plugged as <br />the situation warrants. BLM has developed and currently <br />maintains a water-use inventory to identify and <br />characterize water uses and ~espective sources on public <br />lands. Saline springs will be identified through the <br />program. Control of saline springs will be analyzed <br />through BLM's planning process, with major sources brought <br />to the attention of Reclamation. An example of this is the <br />Sinbad Valley Unit in western Colorado. In September 1986, <br />all advance planning activities for the Sinbad Valley Vnlt <br />were transferred to Reclamation, <br /> <br />-43- <br /> <br />.<l <br />