2015-09-22_HYDROLOGY - M1986079

• Permit No: M1986079
• IBM Index Class Name: HYDROLOGY
• Doc Date: 9/22/2015
• Doc Name: Sub Water Supply Plan
• From: DWP
• To: DRMS
• Email Name: TOD
• Media Type: D
• Archive: No

Rick Parsons
MEtG SWSP
September 17, 2015
Page 4 of 8
Applicant is hereby notified that any renewal request for this SWSP that proposes to use
the 50 Polly Mann shares, must clearly define how the maximum irrigation efficiency was
determined, including all assumptions and calculations. In addition information must
include a maximum efficiency that considers the site specific potential efficiency and the
effects of installation, management and maintenance of the irrigation system on the
potential irrigation efficiency. If the requested information is not provide with any
renewal request the use of the 50 Polly Mann shares as a replacement water source in the
SWSP will not be approved.
Irrigation return flows were distributed with 67 percent attributed to deep percolation
and 33 percent to surface runoff based upon conditions evidenced during site visits, discussions
with irrigators and ditch company personnel, and a review of other studies and change cases
within the basin. The surface runoff (tailwater) return flows are assumed to return to the South
Platte River during the same month of diversion and thus they were not lagged to the river. The
deep percolation was lagged to the river using the same AWAS software and aquifer properties as
described in the Depletions section. Return flows associated with ditch loss were not included in
this analysis since these losses will continue as water is conveyed through the ditch to the pit.
Over a 40 -year study period, the average pro rata diversion for the Polly Mann property
was 179.2 acre-feet per year, which translates to a historic farm headgate delivery of 143.3 acre
feet per year, or 2.87 acre-feet per share per year. The average irrigation water requirement
(IWR) for the Polly Mann property was found to be 93 acre-feet per year which was based on
46.1 acres of irrigation evenly split between alfalfa, corn, and pasture grass. In total, the
historic consumptive use for the Polly Mann property was found to be 87.2 acre-feet per year, or
1.74 acre-feet per share per year. The surface water, or tailwater, runoff averaged 18.7 acre-
feet per year and the deep percolation runoff averaged 37.5 acre-feet per year. The total
return flows represent approximately 39% of the historical farm headgate delivery, or 1.12 acre-
feet per share. The monthly HCU factors as a percentage of lateral deliveries and the winter
time return flows as a percentage of irrigation season's consumptive use credits are as shown in
the table below:
Polly Mann Fulton Ditch Shares Factors
In 2013 and 2014, the water attributable to a portion of the 61 Fulton Ditch shares was
delivered into the pit during the irrigation season. Starting again in 2015 some of the water
attributable to the 49 Fulton Ditch shares will be delivered into the Polly Mann pit recharge
during the irrigation season. For the purpose of this SWSP deliveries to the Polly Mann pit for
recharge shall be limited to the annual long term average of 143.3 acre-feet or the monthly
values listed in the table below:
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
CU as % of
Diversion
-
-
-
55.9
69.7
71.5
71.6
67.5
59.8
41.5
-
-
Replacement as
% of Summer CU
1.0
0.8
0.7
-
-
-
-
-
-
-
1.2
1.2
In 2013 and 2014, the water attributable to a portion of the 61 Fulton Ditch shares was
delivered into the pit during the irrigation season. Starting again in 2015 some of the water
attributable to the 49 Fulton Ditch shares will be delivered into the Polly Mann pit recharge
during the irrigation season. For the purpose of this SWSP deliveries to the Polly Mann pit for
recharge shall be limited to the annual long term average of 143.3 acre-feet or the monthly
values listed in the table below: