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Second Submittal <br /> Comparison of Figure 12 to Figure 3 shows good correlation between model simulated <br /> groundwater elevations and flow directions and those measured in the field. <br /> 4.3 Parameter/Boundary Sensitivity <br /> A sensitivity analysis examines how changing variables within their acceptable range <br /> affects the calibration results. Because the model domain contains so many internal <br /> boundaries, the model is relatively insensitive to hydraulic parameters. It is very sensitive <br /> to the physical construct of the internal boundaries. For example, changing the elevation <br /> of the bottom of the ditch in the area of the nearby wells has a direct correlation to the <br /> ,simulated water elevation in the well. Because the physical nature of ditches and other <br /> internal boundaries are fairly well known or limited (e.g., agricultural drains are typically <br /> less than five and no more than 10 feet below ground surface),the model sensitivity is less <br /> critical. <br /> 4.4 Discussion <br /> The statistics and plot§howing in Figure 11 indicate that the model successfully mimicked <br /> groundwater, elevation distributions near the Site for the existing conditions. Visual <br /> examination of the scatter around the best fit line and calculated slope of the best fit line of <br /> 1.0 indicates that the model does not have bias in the groundwater level predictions and the <br /> groundwater flow direction. During the irrigation season,the model is highly constrained, <br /> meaning that water elevations are significantly controlled by internal boundary conditions <br /> (i.e., irrigation ditches). Given that the approach for this modeling effort was to use CDSS <br /> parameters, the main adjustments that could be made were to the behavior of the irrigation <br /> ditches. <br /> On the Front Range of Colorado, a rule of thumb is that irrigation ditches lose from 10% <br /> to 25% of the water diverted from the river (known as shrink). Using this as a guide, the <br /> overall leakage from the Little Cache and the Taylor and Gill were adjusted until an <br /> acceptable match between the simulated and observed heads was achieved. <br /> Loveland Ready-Mix Concrete 16 Telesto Solutions,Inc. <br /> 20180112grouna-mdr_2ml unnunale«x January 2018 <br />