SPDSS_Task66-2_CollectDevelopMunicipalIndustrialConsumptiveUseEstimates

• Title: SPDSS Task 66.2 - Collect and Develop Municipal and Industrial Consumptive Use Estimates
• Description: This memorandum presents the general approach used to develop municipal and industrial consumptive use for the CU and Losses Summary Report and estimate indoor and outdoor water demands, consumptive use, and return flows for SPDSS modeling efforts.
• Decision Support - Doc Type: Task Memorandum
• Date: 11/14/2007
• 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

Figure 5
Cottonwood Curve

70%

60%

U 50%
"~
CL
CL
~

.~ 40%
0
E~
30%
c

~ 20%

a
16.1%
10%

0%

0% 25% 50% 75% 100% 125% 150% 175% 200% 225% 250% 275% 300%
Total Application /Potential CU
The general rate for estimating the annual volume of LIRFs and CU rate for outside water
deliveries, based on the Cottonwood analysis, is through a detailed study of treated water
deliveries and measured irrigated area on a sub-set of homes within a municipal service area.
This approach was used by the following entities listed in Table 3:
• Aurora • Sterling
• Brighton • Thornton
• DWB • Westminster
• SACWSD
The following information is typically required for these analyses:
• Amount of outside water use applied to lawns (generally equal to total treated water
deliveries minus in-house use deliveries less spray losses and miscellaneous outside uses,
including surface water runoff)
• Amount of precipitation
• Amount of irrigated lawn area
The Cottonwood Curve analyses on the sub-set of homes were summarized by the municipalities
on an annual basis. The amount of return flow and CU rate, as a percent of water applied to
outside uses, is then pulled from the Cottonwood Curve. In Water Court applications for use in
municipal accounting of lawn return flows, municipalities have typically either included a fixed
annual LIRF percentage based on the detailed study, or variable annual LIRF percentages that
require annual Cottonwood Curve calculations.
The Cottonwood Curve method is fairly data-intensive and requires information related to
irrigated acreage within municipal service areas. Rather than carrying out this dynamic analysis
Potential CU - Detemvne by using modified Blaney-Griddle procedure with following
crop coefficients: Apr-1.65; May-1.30; Jun-1.10; Jul-0.95; Aug-0.95, Sep-1.10; Oct-1.20
TotalApplication bawd on amount ofAnnualOutside Water Use (equal
to TotalUse less In-house Use minus spray losses and assorted losses)

X-Oto 55 Y-0
hquations for C~irve X = 55 to 160 Y- 0.357 * (X - 55)
X> 160 Y=100 * (X - 100)

Task 66.2 Memorandum.doc Page 14 of 26