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The presence of South Platte River adds another special type of boundary to the <br />model that must be carefully set-up to achieve a valid simulation. In the case of <br />typical creeks and rivers in the arid west, it is common practice to include the live <br />channel as well as the main stream alluvial channel of the creek as part of the <br />overall stream system. The interconnection of that set of stream cells (with the <br />underlying aquifer is simulated through a representation of the bottom of the <br />alluvial channel that allows flow of water to and from the underlying aquifer <br />depending on the relative head of the live flow and the ambient head in the <br />aquifer at that particular cell. <br />The model requires for each stream cell input, a value for the parameter known as <br />stream conductance. This conductance factor is a composite number made up of <br />the surface area of the stream-alluvium as it traverses the cell, the relative; vertical <br />hydraulic conductivity of the bottom of the stream channel, and the thickness of <br />any less conductive layer that may be present at the base of the alluvial <br />In the subject model, the length of the stream channel in each cell was ieasured <br />from topographic maps, the width was set at 75-feet throughout,'and the leakage <br />factor (the ratio of the vertical hydraulic conductivity and the thicknesls of the <br />lower conductivity layer, or "k/m" ratio) was derived from publishes <br />utilized by the State Engineer's Office. These factors were combined for f <br />to generate the conductance values used. The conductance values <br />combined factors that can allow for quick relative adjustment through th <br />multipliers. This is important in that it is very difficult to derive empirical <br />7 <br />values <br />ch cell <br />e thus <br />use of <br />'ata on <br />Martin and Wood Water Consultants, Inc. <br />