SPDSS_Task56_ConveyanceandApplicationEfficiencies

• Title: SPDSS Task 56 - Conveyance and Application Efficiencies
• Description: This memorandum describes the approach and results obtained under Task 56 - Conveyance and Application Efficiencies. This task includes an estimation of both ditch system conveyance and maximum application ‎(on-farm)‎ efficiencies likely to be experienced in the South Platte basin, plus a recommendation on efficiencies to use for the historic consumptive use analyses.
• Decision Support - Doc Type: Task Memorandum
• Date: 4/22/2008
• 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

• Efficiencies provided through interviews with water administrators and ditch
companies were compiled (SPDSS Task 5), and
• Numerous governmental agencies were contacted, including county offices of
the Natural Resources Conservation Service and the Farm Services Agency.
These inquiries yielded estimates of ditch efficiencies for 69 of the 404 explicitly
modeled surface water structures identified for the South Platte in SPDSS Task 3, which
represents approximately 40 percent of surface water-source acreage. These ditch
efficiencies are recommended for use in StateCU and StateMod modeling efforts.
Attachment A shows the ditch conveyance efficiencies found during the search. For the
remaining key structures in the study area, there is limited information regarding
conveyance losses. Consequently, a search of empirical methods that have been
developed to estimate ditch efficiencies was completed, and an appropriate method
selected, as outlined in Attachment B.
Recommendations -Conveyance Efficiencies
The following is the recommended sequence for estimating conveyance efficiencies:
1. Use ditch efficiencies provided by water administrators, ditch companies, water
rights decrees, and published literature (listed in Attachment A, provides
efficiencies for 69 structures).
2. Estimate conveyance efficiencies for key structures based on canal length and soil
type, using the MRCS approach outlined in Attachment B, using the following
procedure. Note that this procedure was also used to estimate conveyance
efficiencies for the RGDSS consumptive use analysis.
• Determine canal lengths using the GIS CDSS Toolbox "Aggregated Canal
Segments" tool. The required input file is the SPDSS Canal coverage. The
comma-separated output file lists WDID and canal length in feet.
• Determine average weighted ditch permeability using the GIS CDSS
Toolbox "Soil Parameter by User Supplied Polyline ID" tool. The required
input files include the Statewide STATSGO Permeability coverage and
the SPDSS Canal coverage. The comma-separated output file lists WDID
and average canal permeability.
• Based on soil permeability, determine soil classification by canal (see
relationship in Table B-3, Attachment B).
• Based on the soil classification and canal length, select corresponding
efficiency as described in the approach section.
3. Estimate conveyance efficiency for aggregate structures and key structures
without canal length information using the MRCS approach outlined above, based
average conveyance loss determined by aggregate area as follows:
• Estimate ditch length to be the median length of ditches with values
estimated in step 2 above.
• Determine average weighted ditch permeability using the GIS CDSS
Toolbox "Soil Parameter by User Supplied Polygon ID" tool. The required
input files include the Statewide STATSGO Permeability coverage and
the SPDSS Aggregate polygon coverage developed in Task 3 -Aggregate
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