CRDSS_Task1_15-17_AnalysisOfIrrigationandMunicipleReturnFlows

• Title: CRDSS Task 1.15-17 - Water Rights Planning Model - Ana;ysis of Irrigation and Municipal Return Flows
• Description: This memorandum generally describes procedures ‎(the Glover solution)‎ to estimate the timing of irrigation return flows and summarizes the results of a theoretical return flow analysis.
• Decision Support - Doc Type: Task Memorandum
• Date: 1/9/1995
• DSS Category: Surface Water
• DSS: Colorado River
• Basin: Colorado Mainstem
• Contract/PO #: C153658, C153727, C153752
• Grant Type: Non-Reimbursable
• Bill Number: SB92-87, HB93-1273, SB94-029, HB95-1155, SB96-153, HB97-008
• Prepared By: Riverside Technology inc.

optional patterns of stream depletion coefficients have been determined using assumptions for idealized
monthly diversions, representative irrigation consumptive use and the three return flow patterns shown
above. By selecting one of the four options, the user will be able to specify monthly depletion
distribution coefficients that can be used to relate annual irrigation consumptive use to monthly
streamflow depletion. For option Nos. 1, 2, and 3, the default depletion coefficients are given in Table 3.
TABLE 3
STREAM DEPLETION COEFFICIENTS
MONTHOPTION 1OPTION 2OPTION 3
January0.0-3.5-11.5
February0.0-3.3-10.8
March0.0-3.1-10.2
April0.0-2.9-9.6
May20.324.337.5
June35.145.472.6
July27.836.455.7
August18.222.831.4
September-1.1-4.1-14.9
October-0.3-4.4-14.6
November0.0-4.0-13.4
December0.0-3.8-12.5
Total100.0100.0100.0
Option No. 4 would allow the user to specify depletion distribution coefficients that are different from
the default values shown above. The optional depletion distribution coefficients were derived using the
three return flow patterns described above. For return flow patterns that lag for many years (pattern Nos.
2 and 3), the depletion distribution coefficients were adjusted by assuming a sufficiently long enough
period of time for the return flows to approach equilibrium.
Municipal Return Flows
For return flow considerations in the water rights planning model and in order to estimate the natural
corenatfl
(virgin) streamflow at USGS gaging stations using , the return flows and depletions resulting
corenatfl
from municipal uses will need to be estimated. allows the user to specify one of two options
for monthly municipal return flow factors. Option No. 1 provides the monthly default factors shown in
Table 4.
TABLE 4
MUNICIPAL RETURN FLOW FACTORS
JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC
0.900.880.860.560.450.380.390.440.5 6 0.741.000.90
Option No. 2 will allow the user to specify factors that are different from the default values. For the
municipal return flow analysis, a typical monthly distribution of municipal demands was adopted for an
assumed annual demand of 10,000 acre-feet. The results are not dependent on the assumed annual
municipal demand; however, results are dependent on the assumed monthly distribution. Monthly in-
house water use was assumed to be the average of the monthly values for December, January, and
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A275 01.09.95 1.15-17 Hyre, Fosha