RGDSS_Task8-2_HistoricMonthlyModel_ReviewGroundwaterEfficiencies

• Title: RGDSS Task 8-2 - Phase 1c Historic Monthly Model - Review Efficiencies of Groundwater Systems
• Description: Memo documenting efficiencies of groundwater systems.
• Decision Support - Doc Type: Task Memorandum
• Date: 9/8/2000
• DSS Category: Surface Water
• DSS: Rio Grande
• Basin: Rio Grande
• Contract/PO #: C153863
• Grant Type: Non-Reimbursable
• Bill Number: HB98-1189, SB99-173
• Prepared By: Leonard Rice Engineering

RGDSS Memorandum
Final
TO: Ray Bennett
FROM: Ed Armbruster, Hydrosphere
SUBJECT: RGDSS Surface Water, Task 6.3 -Determine Key Structure Efficiencies,
and Task 8.2 -Review Efficiencies of Groundwater Systems
Memorandum
DATE: September 8, 2000
CC: Randy Seaholm
Introduction
This memorandum represents delivery associated with Task 6.3 (Determine Key Structure
Efficiencies) and Task 8.2 (Review Efficiencies of Groundwater Systems Memorandum). The
objectives of these task was as follows:
6.3 Review a memorandum documenting efficiencies of surface water use and select
efficiencies for use in the surface water model
8.2 Review memorandum documenting efficiencies of groundwater use and select
efficiencies for use in the surface water model.
Review of Efficiency Memorandum
The Consumptive Use contractor on the RGDSS project estimated conveyance, on-farm and
overall system efficiencies of agricultural water use in the San Luis Valley. This effort is
described in a memorandum documenting Task 3.8 of the Consumptive Use Scope of Work
(July 20, 1999) The following is a summary of this work, and rationale for selecting
efficiencies for use in the Rio Grande Surface Water Model.
Efficiency information was developed by the Consumptive Use Contractor based on
information gathered from managers of several large ditch companies, results of local gain/loss
studies, examination of physical characteristics (capacities, widths, lengths) of ditches and
canals, review of water application techniques, soil characteristics and cropping. Estimates of
conveyance and on-farm efficiencies were developed separately, then this information was
combined to estimate overall system efficiencies. Estimated efficiencies were then checked for
appropriateness against a variety of published data for the San Luis Valley and similar
agricultural areas.
The results of the Consumptive Use Contractor's effort for surface irrigation ditches are shown
in Table 1. Note that system efficiency estimates are provided separately for the first month of
irrigation and for after the first month of irrigation. Separate estimates were developed to
reflect higher losses when initially canal wetting occurs at the start of the irrigation season.
Also note that Table 1 represents efficiency ranges by Water District. Differences between the
eight Districts reflect varying irrigation techniques, soil types and ditch/canal condition that
occur across the San Luis Valley.
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