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<br />~ <br />w <br />c:h' " <br />CJ,';.l <br /> <br />18 <br /> <br />mentioned above, surficial materials were studied in Basins A, N, Q, <br /> <br />S, T, and U, only. <br /> <br />. <br /> <br />Soil and weathered bedrock samples were collected for SMC <br /> <br />analysis at the same sites that soil depth measurements were recorded. <br /> <br />For the soil samples, each sample contained a column of material from <br /> <br />the surface to the top of the weathered bedrock. The weathered <br /> <br />bedrock samples contained a column of the top 10-15 cm of that <br /> <br />material. A few samples of alluvium were collected for analysis, also. <br /> <br />The samples were analyzed for SMC by a method very similar <br /> <br />to that outlined by Laronne (1977). Laronne observed that many <br /> <br />fragments of material did not break down during his procedure, so <br /> <br />that the total SMC of his samples were not derived. Therefore, this <br /> <br />procedure differs from Laronne's in that the samples were pulverized <br /> <br />and sieved in order to provide silt- and clay-sized particles only. <br /> <br />Laronne (1977) observed 10,000 ppm solid sediment con centra- <br /> <br />tion in samples collected from a flash flood in the study area. He <br /> <br />simulated the flood water in the laboratory by using a 1:99 sediment: <br /> <br />water mixture. Consequently, the SMC in percent was' calculated and <br /> <br />used herein as follows: <br /> <br />3 ' 3 <br />SMC = [(TDSl:99 mg/9,)(g/lO mg)(9,/IO m)(99 m9,/g)] (l00) <br /> <br />= (TDSl:99)(0.0099) <br /> <br />(4.1) <br /> <br />SMC is related to the total dissolved solids (TDS) of a solution <br /> <br />which, in turn, is related to the specific electrical conductance (EC) <br /> <br />of a solution. The relationship between TDS and EC for Mancos Shale <br /> <br />materials in Grand Valley, as derived by Laronne, is as follows: <br /> <br />log (TDS) = -0.47413 + 1.1212 log (EC) <br /> <br />(4.2) <br />