BOARD00223

• Board Meeting Date: 9/13/2004
• Description: ISF Section - Proposed Water Right Donation - Colorado Water Trust, Peabody #1 Ditch and Lund Enlargement, Boulder Creek and Blue River
• Board Meetings - Doc Type: Memo

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MEMO

To:

From:

Subject:

Date:

Anne Janicki, Colorado Water Conservation Board
Chris Weber & Mike Sayler
Peabody Ditch No. I Depletion Analysis
August 25, 2004

Introduction

We have prepared this memo summarizing the results of our depletion analysis for the Peabody No.
I Ditch and the Lund Enlargement and Expansion as requested. This updates the depletion analysis
portion of our May 26, 1995 historic use letter report.

The previous analysis was run on a monthly time-step using average diversions from the 1970 to 1990
period. We have expanded this period to 1965 to 2002 based on available diversion records and run
the analysis for each year rather than for the average of the period. We then expanded the period from
1904 (senior right date of appropriation is May 23, 1904) to 2003 using averages to estimate the data
prior to 1965. To determine the depletions associated with the senior right, we separated out the
diversions taken under the senior right (all diversions up to the first five cfs) and ran a separate
depletion analysis. We also remeasured the historic irrigated acreage under the Peabody Ditch No.
I. To determine a more local average annual consumptive crop irrigation requirement (CIR) value,
a Blaney-Criddle analysis was completed using high altitude crop coefficients determined in nearby
Grand County. We applied a 15% ditch loss to the diversions and a 50% maximum fann efficiency
to the farm headgate deliveries, which were the same percentages used in our previous analysis. Due
to the close proximity of the irrigated land to the stream, we assumed surface runoff and groundwater
return flows returned to the stream within a month of application, so lagging was not factored in the
analysis. The following paragraphs describe the analysis in more detail.

I. Diversions and Study Period - Ourprevious depletion analysis used average diversions from
1970 to 1990. We have extended that period to 1965 to 2002 based on available diversion
records. There were some missing years in the diversion records. We then expanded the
diversion table (Table I) to cover the period from 1904 to 2003 and filled in missing years in
the diversion re.cords with the average values from the years with records. For the period from
1904 to 1914, only the average diversions for the senior right (782 ac-ft/yr) were used since
the junior rights were not appropriated until May 15, 1915. The average was based on the
period from 1965 to 1990 since this is the period of record that would most likely represent
longer term historic irrigation practices and diversions. To estimate historic diversions for the
period from 1915 to 1964 and the missing data for 1968,1974,1975, 1979, 1980 and 1982,
we used the average total diversions from 1965 to 1990 (866 ac-ft/yr). Diversions ceased in
2000, so we assumed 2003 to also have no diversions. Average diversions for the entire 1904
to 2003 period are about 771 ac-ft/yr. To help establish terms and conditions for the water
court change of use, we broke out the diversions by senior and junior right shown in Tables
2 and 3. The combined diversions during the 1904 to 1914 period averages in zeros for the
junior right. The average senior right diversions for the 1904 to 2003 period are 707.8 ac-ft,
while the average junior diversions for the 1915 to 2003 period are 71.5 ac-ft, for a total of