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<br /> <br />LONG-TERM SEDIMENT ACCUMULATION IN RETENTION BASINS IN MANCOS SHALE BADLANDS6 <br /> <br />w <br />w <br />-.J <br />(')1 <br /> <br />Background <br /> <br />Erosion and sediment transport from surface runoff on saline shale lands have <br />been identified elsewhere in the report as an important mechanism for salinity <br />production. The results of rainfall simulation studies indicate that this <br />process is particularly important on steep dissected Mancos shale badlands. <br />The purpose of this study was to quantify long-term yields of sediment (and, <br />by inference, salt) from unvegetated, steep dissected Mancos shale badlands. <br />A series of gully plugs installed by BLW with bulldozers near Huntington, <br />Utah, offered a source of sediment yield data (Fig. 10). The plugs were in- <br />stalled in the early 1970's to reduce flash flooding and sediment transport <br />from Mancos shale badlands to the Huntington irrigation canal. The plugs were <br />believed to be 100% efficient in trapping all runoff and sediments. <br /> <br />~ <br /> <br />POWER LINE <br /> <br />O:::>t!)'O-; <br />. ....~...4 <br />Plug. 1-4, 12 ......./ <br />I. <br />/ '. <br />, ...... <br />. <br />HUNTINGTON CANAL" <br /> <br />t <br /> <br /> <br />HUNTINGTON <br /> <br /> <br />18 km <br /> <br />, <br /> <br />Plug. 8-11 <br /> <br />CASTLE DALE <br /> <br />Figure 10. Location of Huntington, Utah, sediment yield study. <br /> <br />We selected 12 basins for study in drainages ranging from 820 to 13,000 m2 <br />(0.2~3.2 acres) in area. Numerous holes were drilled in each deposit, accumu- <br />lations were mapped, and bulk densities measured. Annual precipitation data <br />was gathered from four stations in the surrounding area (Table 7). <br /> <br />6 Detailed study results provided in Jackson and Ju1ander (1982). <br /> <br />28 <br />