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Table 1 - Results from falling -head permeameter tests to quantify the streambed <br />hydraulic conductivity, Ksb (m -d -1), of the South Platte River. <br />Ksb Ksb <br />Darcy's Equation Hvorslev (1951) Equation <br />South Platte River <br />L =25 cm <br />L =40 cm <br />L =25 cm <br />L =40 cm <br />1 <br />142.8 <br />83.2 <br />167.6 <br />92.3 <br />2 <br />138.1 <br />68.0 <br />162.1 <br />75.4 <br />3 <br />143.6 <br />47.8 <br />168.5 <br />53.1 <br />4 <br />132.4 <br />47.7 <br />155.5 <br />52.9 <br />5 <br />161.6 <br />74.7 <br />189.8 <br />82.8 <br />The hydraulic conductivity of the sloughbed was also estimated using a falling - <br />head permeameter test. Data and results for one of the backwater slough measurement <br />locations are shown in Table 2 and suggest that a considerable permeability difference is <br />present (i.e., Ksb <1.0 m -d "1). Streambed materials in the slough consisted of coarse sands <br />and gravels similar to the South Platte River, but were much more inundated by organic <br />materials that significantly limited the exchange of water between the slough channel and <br />alluvial aquifer. The thickness of this organically restricted layer is approximated to be <br />50 cm. Data from additional falling -head permeameter tests estimate the sloughbed <br />hydraulic conductivity between 0.1 and 1.0 m -d-1. A picture of the conditions <br />representative of the slough channel at the Tamarack research site is shown in Figure 3. <br />Table 2 - Falling -head permeameter test for determining the hydraulic conductivity <br />of the sloughbed at the Tamarack State Wildlife Area. <br />Initial Data <br />Length of Permeameter in Streambed, L (cm) <br />25.00 <br />Cm <br />Diameter of Permeameter, D (cm) <br />15.24 <br />Cm <br />Initial Water Level, HW (cm) <br />21.00 <br />Cm <br />Initial Displacement, Mo (cm) <br />44.50 <br />Cm <br />Initial Head, Ho (cm) <br />23.50 <br />Cm <br />Falling -Head Permeameter Data <br />Estimated Ksb (m -d-1) <br />Time, t (min) <br />Displacement, M; <br />Head, H; <br />Darcy <br />Hvorslev <br />0.00 <br />44.50 <br />23.50 <br />43.00 <br />44.30 <br />23.30 <br />0.072 <br />0.084 <br />72.20 <br />44.05 <br />23.05 <br />0.096 <br />0.113 <br />105.20 <br />43.95 <br />22.95 <br />0.081 <br />0.095 <br />139.20 <br />43.60 <br />22.60 <br />0.101 <br />0.119 <br />5 <br />