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Fork Slater Cr - Lower above the LT by multiplying the "adjusted" gage discharge values by an <br />area ratio; specifically, the area of South Fork Slater Cr - Lower above the LT (16.64 mi ) to <br />North Fork Elkhead Creek Near Elkhead, CO (21.00 mi) . The resulting proportioned <br />hydrograph was itself "adjusted" (decreased) to reflect the consumptive irrigation depletions and <br />out -of -basin diversions upstream of the LT. The final hydrograph thus represents a distribution <br />of flow over time that has been reduced to reflect existing human uses. <br />{The Following discussion is based upon the US Geological Survey's Techniques of Water - <br />Resources Investigations Series, Book 4: Hydrologic Analysis and Interpretation, Chapter A3: <br />Statistical Methods in Water Resources (Chapter 3: Describing Uncertainty) by D.R. Helsel and <br />R. M. Hirsch. This technical reference provides the scientific background and guidance <br />important to the systematic interpretation of hydrologic data. The document is available online <br />and is a valuable aid to understanding and interpreting the analyses described here.) <br />The next step in producing a representation of the discharge at South Fork Slater Cr - Lower is to <br />compute the Geometric Mean of the area- prorated "adjusted" data values from the North Fork <br />Elkhead Creek Near Elkhead, CO hydrograph. This step is of value because of the inherent <br />statistical weaknesses found in any collection of data intended to measure natural stream <br />discharge. Without getting into the details of statistical theory, it is worth noting that a set of <br />discharge measurements is inherently inaccurate, no matter how well collected, due to the <br />difficulties attendant to data collection, especially hydrologic data. To give deference to this fact <br />and to increase the value of the hydrograph product of this analysis, the Geometric Means of the <br />data were computed and plotted along with the 95% Confidence Intervals about the data. The <br />resultant hydrograph, including recommended Instream Flow values, is displayed in figure 1. <br />-5- <br />