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Last modified
1/26/2010 12:51:46 PM
Creation date
10/11/2006 11:55:29 PM
Metadata
Fields
Template:
Water Supply Protection
File Number
8276.300
Description
Lower Gunnison Basin Unit - Colorado River Basin Salinity Control Project
State
CO
Basin
Colorado Mainstem
Water Division
4
Date
12/1/1989
Title
Colorado River Water Quality Improvement Program Lower Gunnison Basin Unit North Fork Area Preliminary Findings Report December 1989
Water Supply Pro - Doc Type
Report/Study
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<br />~c <br />I.', <br />pl' <br /> <br />fi~ <br />'-'''., <br />r~ <br /> <br />;;t,R <br />};;1 <br />,J <br /> <br />~'1 <br />t;: <br />,t-, <br />~".j <br /> <br />~':1 <br />:::.:.~ <br /> <br />-:- ~; <br /> <br />t4 <br />'j <br />.. <br />:V <br /> <br />iI"'_~ <br />l""l <br />r~ <br />"""" <br /> <br />"il <br />1/' <br />~.. <br />~1 <br /> <br />f:'~ <br /> <br />t:J <br /> <br />'''' <br />~-_ l <br />\"j <br />, .. <br />(:?! <br /> <br />F:1 <br />k.'t <br /> <br />!.'.?: <br /> <br />1;;'1 <br />\\.,..j <br /> <br />f'.~ <br />k~ <br />LJ <br /> <br />~~:j <br />~1) <br /> <br />,. <br />,. <br /> <br />CHAPTER II <br /> <br />PIAN P'ORMULATIOO <br /> <br />The Surface Creek gauging station near Cedaredge was the source of data <br />on inflow water quality and quantity. Water quality and the relationship <br />between quantity and drainage area for the Tongue Creek inflows were assumed <br />to be similar to those recorded at the Surface Creek gauge. Assuming that the <br />flow and salt tonnage developed for the Tongue Creek (Cory) gauging station <br />are correctly defined and the inflow quality as defined by the Surface Creek <br />gauging station near Cedaredge is accurate to or ~ 100 percent, then the salt <br />load associated with the drain base flow component ranges from 41,600 to <br />42,600 tons. Based on this sensitivity analysis, the inflow salt load appears <br />to have no significant effect on the results of the base flow separation. <br /> <br />Over the period April 1976 to March 1984, the annual fluctuation in drain <br />base flow volume is considerable. These base flow values range from a low of <br />4,170 acre-feet in the 1977-1978 drought year to a high of 29,730 acre-feet in <br />the 1983-84 record runoff year. Using these drain base flow volumes to <br />calculate total annual salt loads for the Tongue Creek drainage results in <br />values of 44,500 and 45,500 tons/year, respectively. With the high variation <br />in annual drain base flow volume which corresponds closely to the historic <br />runoff data, there is no possibility of it being induced by irrigation <br />practices exclusively. <br /> <br />Studies in the Reed Wash area in the Grand Valley Unit indicated that <br />canal and lateral seepage accounted for less than 40 percent of the drain base <br />flow tonnage, with on-farm seepage and deep percolation accounting for greater <br />than 60 percent. Applying this distribution of salinity contributions to the <br />Tongue Creek drainage and assuming that the drain base flow value of <br />42,600 tons is due equally to natural precipitation and irrigation practices, <br />the base flow tonnage associated with canal and lateral seepage is 8,520 tons <br />in the Tongue Creek drainage. <br /> <br />Cost Effectiveness Analysis <br /> <br />Cost estimates were developed for lining all irrigation ditch systems <br />where inventory data was available (102 of 267 systems or approximately <br />38 percent). These cost estimates were based on unit costs developed from the <br />Grand Valley Unit, Stage 'lWo development. Annual costs were determined using <br />an 8-5/S-percent interest rate, 50-year replacement period, and annual O&M <br />costs derived from the Grand Valley Unit development. A cost effectiveness <br />evaluation was then conducted using a range of seepage rates from O.l to <br />0.9 feet per day. The analysis indicated that to obtain a cost effectiveness <br />value of $100 per ton or less, 70 percent of the total Tongue Creek salt load <br />(or approximately 30,000 tons per year) would need to be removed by lining <br />38 percent of the irrigation systems in the drainage. This amount of salt <br />load reduction is not possible since the base flow separation analysis <br />indicated that only 8,520 tons were attributable to canal and lateral seepage. <br />Based on this cost effectiveness analysis the Tongue Creek drainage (with the <br />exception of the Oak Creek subbasin) was eliminated from further <br />investigation. <br /> <br />000934 <br /> <br />8 <br />
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