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This document contains the information required of Colorado's depletions plan for the South Platte basin for the
<br />Initial Reporting Period ending on January 1, 2009 (two years from the initiation of the Program) and the required
<br />information for the next 5 -year reporting period. Please also see the attached April 10, 2009 memorandum from
<br />Ray Alvarado to Ted Kowalski wherein he provides information on the net changes in irrigated acreage in the South
<br />Platte basin. The Governance Committee approved March 31, 2009 with an extension to April 30, 2009 as the
<br />deadline for reporting the requisite information to the Governance Committee.
<br />Executive Summary
<br />The actual population at the end of the Initial Reporting Period and the projected population increase for the ensuing
<br />Reporting Period are included in the attached report from the Colorado State Demography Office. The population
<br />increase from the PRRIP baseline date of July 1, 1997 to January 1, 2009 (end of initial reporting period) is 750,831
<br />and the projected increase from the baseline date to January 1, 2014 (end of next 5 -year reporting period) is
<br />expected to be 1,014,114. The population increase as of 2009 indicates faster population growth than originally
<br />predicted in 1997.
<br />Data related to the original assumptions concerning per capita water use, supply source mix by region, and
<br />population served was collected by a questionnaire filled out and returned from 30 municipal entities, representing
<br />77% of the population growth since 1997 in the South Platte Basin. This data was collected for an initial 5 -year
<br />period of 1998 -2002 period and the most recent/current 5 -year period of 2004 -2008. This report incorporates
<br />additional data from the State of Colorado regarding updated water conservation information and utilizes water
<br />administration records ( "daily river call data") for determining the availability of native South Platte water rights
<br />junior to July 1, 1997. All of this information was used to adjust the original assumptions on the mix of the six
<br />sources to better reflect the actual water supply mix serving population growth since the start of PRRIP on January
<br />1, 2007 and this adjustment is shown in Table 113. The new percent mix of the six sources shows that the biggest
<br />adjustment is in water conservation, more than doubling the percent overall, which is reflective of the response to
<br />recent drought conditions. Due to the drought, the availability of South Platte native flows under a junior water right
<br />has diminished by about half. The data received from the municipalities and the State were also used to compute a
<br />revised gross per capita water requirement of 0.2504 acre - feet/person/year (original value was 0.27), which will be
<br />used along with the revised percent mix of water sources in the CPFD accretive /depletive effect analysis since the
<br />start of the Program on January 1, 2007.
<br />Figures 1 A (2007), 1 B (2008), 1 C (2009), and 1 D (2013) show the monthly accretive /depletive effect of each of the
<br />six sources and the cumulative effect at the Stateline for each of these years. For the initial reporting period of 2007
<br />and 2008, the cumulative depletive effect in May /June totals 1,564 acre-feet and 1,720 acre -feet respectively,
<br />averaging 1,642 acre -feet for these two years. For the first year 2009 and the last year 2013 of the next 5 -year
<br />reporting period, the cumulative depletive effect in May /June is predicted to total 1,861 acre -feet and 2,366 acre -feet
<br />respectively.
<br />Colorado has developed managed ground water recharge projects and partnerships to retime CPFD accretions
<br />occurring in October through April to offset the May /June depletions. For the initial 2007 -2008 reporting period,
<br />Table 4 shows the mitigation accounting where an average of 2,502 acre -feet of retuned recharge return flows in
<br />May /June adequately replaces the average 1,642 acre -feet depletion for these two years.
<br />Population Reports
<br />Attached to this Memorandum is a letter report with table from the Colorado State Demography Office (SDO)
<br />listing the populations for the Colorado counties of the South River Basin grouped by the regions (Northern, Central,
<br />Southern) used for the CPFD analysis. The table has two columns for January 1, 2009. The first column (total of
<br />3,448,061) was an estimate last year in Colorado's annual report to the GC dated March 31, 2008 while the second
<br />column (total of 3,470,772) is the current updated January 1, 2009 SDO value for population. The SDO has
<br />indicated that this increase is due to Denver growing faster than expected and the Census Bureau improving their
<br />method of tracking migration. The table also lists the SDO population estimate for January 1, 2014 of 3,734,055.
<br />The SDO population value for the PRRIP baseline of July 1, 1997 given in the SDO table is 2,719,941. The
<br />population increase for July 1, 1997 to the updated January 1, 2009 is 750,831 or 65,289 per year for the 11.5 years
<br />from July 1, 1997 to January 1, 2009. The population increase between January 1, 2009 and January 1, 2014 is
<br />263,283 or 52,657 per year for the 5 years. These differences per year before and after January 1, 2009 are used in
<br />the CPFD analysis to compute depletions and accretions for a given year. The CPFD analysis utilizes a July 1
<br />population for a given year to compute the population increase since the baseline date of July 1, 1997. For example,
<br />for the first year of the Program of 2007, the population increase since July 1, 1997 used in the analysis for July 1,
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