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Figure B-6 <br />Permeability and Soil Type in the South Platte Basin <br />s <br />~ ,.r~--- - . _ - ~ ,/ <br />!~ :'~, <br />~~ +y _ ICY` <br />- ~ '~~/ <br />Lr4end __ _ ~~ <br />Sail Pemleab~IlM ' ~ <br />hmxa6lity I~~.mr I <br />~~: ~: ..,. .... y <br />~'y <br />r <br />~+ v~~ / <br />0 FS 3d 6p Mdes <br />I I l <br />The curves shown in Figure B-5 were developed for ditch systems less than one mile in <br />length. However, that only represents a portion of the total ditch systems in the basin. <br />Therefore, the curves were extended based on the canal loss information for the larger <br />ditches discussed previously. Figures B-7 and B-8 show the MRCS conveyance <br />efficiency curves for ditch lengths up to one mile in sandy loam and sand, respectively, <br />and extrapolated curves based on the estimated ditch loss data from Table B-1. Note that <br />the extrapolated curves developed from the South Platte data are similar to the <br />extrapolated curves developed for the RGDSS effort. Conveyance efficiencies were <br />estimated for all key structures not listed in Table B-1 based on ditch length, <br />permeability, and the extrapolated MRCS conveyance efficiency curves shown in Figures <br />B-7 and B-8 using the CDSS GIS data management tool developed by LRE, which <br />determines alength-weighted permeability for each structure. <br />There has not been a trend towards improving or lining canals and laterals in an attempt <br />to decrease conveyance losses in the South Platte basin. Therefore, the recommended <br />conveyance efficiencies are appropriate for the 1950 to present study period. In addition, <br />the range of conveyance efficiencies is consistent with our knowledge of conveyance <br />efficiencies in areas outside of the South Platte basin with similar soils. <br />Page B8 of B9 <br />