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to data collected at Station #20, the farthest downstream sampling <br /> point on Coal Creek. <br /> 1. Date of Sampling. A fairly complete set of samples was <br /> collected in 1978 and 1979 . Sampling took place, in most <br /> instances, in 2-3 week intervals during that period. From 1980 <br /> through 1992 , flows were measured and samples were collected 2 to <br /> 4 times per year. <br /> 2 . Flow. At station #20, the flow ranges from 2 cfs to 222 cfs. <br /> Data for 1978-1979 indicate clearly that the peak flow occurs in <br /> May. (This fits the general trend in Colorado whereby peak flows <br /> occur about 4-6 weeks after the initiation of snowmelt at high <br /> altitudes . ) <br /> For the years following 1979 , the rate of flow was interpolated for <br /> the May peak based on adjacent samplings . Provided these <br /> interpolations are correct, high flows occurred in 1979, 1980, <br /> 1982 , 1983 , and 1991. Flows for these years are nearly two times <br /> greater than the other years . <br /> Peak flow measurements were collected in 7 out of the 15 years of <br /> data collection. <br /> 3a. Conductivity and TDS . Conductivity and TDS behave in nearly <br /> identical ways (see later sections) . High conductivities and TDS <br /> occur during low flow, probably for two reasons. First, spring <br /> melt dilutes the water relative to the dissolved species because <br /> melt water is relatively free of dissolved species. About the only <br /> materials available for dissolution by snowmelt is dust. <br /> Second, water movement during low flow periods has a greater amount <br /> of time in contact with available soluble species, so greater <br /> portions of soluble minerals are able to be dissolved. Second, <br /> about half of the low flow season occurs in warm weather, and warm <br /> water generally increases the solubility of solids. This latter <br /> point is probably has a minor effect relative to the dilution <br /> effects of the former point, but it is nonetheless a fact worth <br /> considering. <br /> 3b. Conductivity and TDS versus time. Conductivity averages about <br /> 500 and TDS averages about 250 . However, the highest conductivity <br /> and the highest TDS occur from late 1987 through late 1992 . <br /> 3c. Conductivity and TDS versus flow. Conductivity and TDS both <br /> show an inverse exponential relationship with flow. High Cond and <br /> TDS correlate with low flow. <br /> 4a. TSS . Most of the high TSS concentrations occurred during <br /> lower flows . The reason for this in not perfectly known, but is <br /> probably related to installation of sediment retention ponds around <br /> the mid-1980s . The most plausible explanation is that slow flowing <br />