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SPDSS_Task77_PerformAnalysisofDeficitIrrigation
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SPDSS_Task77_PerformAnalysisofDeficitIrrigation
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Last modified
4/17/2013 9:40:02 AM
Creation date
5/27/2008 1:38:47 PM
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Decision Support Systems
Title
SPDSS Task 77 - Perform Analysis of Deficit Irrigation
Description
This memorandum presents the general approach for Task 77: Perform an analysis to determine whether estimating the use of supplemental supplies (i. e. ground water and reservoir releases) to meet full or partial potential use is appropriate for regions within the South Platte.
Decision Support - Doc Type
Task Memorandum
Date
6/13/2006
DSS Category
Consumptive Use
DSS
South Platte
Basin
South Platte
Contract/PO #
C153954
Grant Type
Non-Reimbursable
Bill Number
SB01-157, HB02-1152, SB03-110, HB04-1221, SB05-084, HB06-1313, SB07-122
Prepared By
Leonard Rice Engineering
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These sources were not complete enough to be analyzed. Specifically, both sources are limited <br />by not having associated PCCs and the first source is limited because it only provides annual <br />totals. <br />Historical Augmentation Plans <br />Prior to the early 2000's, there were no decreed augmentation plans or approved substitute water <br />supply plans within the SPDSS study area that were based on pumping records. The standard <br />practice was to base augmentation requirements on pumping demand predicted using an IWR <br />method, typically modified Blaney-Griddle. As discussed in the Task 58 Review Previous <br />Estimates of1'otential CUmemorandum, the Colorado Revised Statues direct applicants to use <br />the modified Blaney-Griddle method to calculate depletions associated with wells for diversions <br />that are not actually measured. Some irrigators did maintain pumping recorded by flow meters <br />or estimated pumping using power records and PCCs. Within the SPDSS study area, irrigators <br />were not required to certify flow meters and PCCs, which are both very sensitive and without <br />proper calibration, can result in records that are not representative of actual pumping. <br />Several recently decreed lower South Platte augmentation plans have augmentation requirements <br />based on actual pumping records multiplied by an application efficiency (generally 80% for <br />sprinklers, 60% for flood). Under some of the larger augmentation plans, users will maintain <br />both flow meter readings and power data that can be used with a certified PCC to estimate <br />pumping. Meters are in the process of being installed and certified. In the coming years, records <br />associated with these new decrees will be valuable for investigating deficit irrigation. <br />Pumping Data Review <br />The GASP (Groundwater Appropriators of the South Platte) database was developed primarily <br />from user-supplied information. Most of the information in this database was derived from <br />power records that were not certified and included estimated pumping and application <br />efficiencies. Based on discussions with individuals who have reviewed and worked with this <br />database, while it may have been sufficient for other uses, its error range is too large to estimate <br />deficit irrigation. <br />Central Colorado Water Conservancy District and other districts are in the process of installing <br />(and certifying) flow meters on individual wells. While Central has some metered flow records <br />available from the past several years, a quota has been applied during this period. The quota <br />limits pumping to a percentage of the estimated demand. With restricted pumping, the records <br />may not be representative of the entire SPDSS study period and therefore were not considered <br />appropriate for characterizing deficit irrigation. <br />Pumping records were requested from several other ditch companies and water districts. The <br />majority of the contacts indicated that pumping records were not available or that they could not <br />obtain the individual users' permission to release the data. Two potential data sets were <br />provided: (1) monthly pumping records associated with several wells located on the eastern <br />plains of the South Platte River Basin, and (2) annual pumping estimates associated with the <br />Northern High Plains area. <br />Task 77.doc 5 of 8 <br />
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