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<br />> <br /> <br />M'~ ~"3 <br />'-' .J _"" .~ <br /> <br />Draft: April 21, 1994 <br /> <br />irrigation depletion estimates) as developed for <br />the Gunnison River at Crystal Dam and Gunnison <br />River at Grand Junction were used as mass balance <br />reference points for Upper Gunnison and Expanded <br />Network natural flows, respectively (inflows sum to <br />reference stations) <br /> <br />natural flows at core stations were adjusted to <br />eliminate negative values in difference files <br />representing gains from intervening areas between <br />core stations; <br /> <br />natural flow estimates for ungaged sites above <br />core stations or within intervening areas between <br />core stations were derived by: <br /> <br />setting it equal to the difference between <br />core station values <br />proportioning-difference files according <br />to area or area weighted elevation derived <br />yields <br /> <br />or <br /> <br />developing annual yield estimates from <br />elevation/yield curves, with monthly <br />distribution based on core station patterns <br />(or application of flow factors derived from <br />additional available gage data) <br /> <br />review indicated that in many cases, zero flows occur <br />in flows derived from difference files (core station <br />difference file or core station / elevation yield curve <br />derived inflow difference file); <br /> <br />generally, these inflows represent lower <br />elevation, lower yield contributing areas <br />it was pointed out that in addition to estimates <br />of inflow gains, inflows based on difference files <br />reflect errors made in core station/elevation yield <br />curve derived flows (including gaging errors, <br />assumed depletion rates, irrigated acreage and <br />cropping pattern estimates,monthly flow <br />distribution patterns, extension of records, return <br />flow timing, evaporation, etc.) <br /> <br />discussions also indicated that some zero flow <br />occurrences may be due to rounding (i.e., values are <br />presented in 1000 acre feet, rounded to the nearest 100 <br />acre feet; a flow of 49 acre feet is shown as 0.0; 51 <br /> <br />3 <br />