WSP08430

• File Number: 8200.760
• Description: Yampa River General
• State: CO
• Basin: Yampa/White
• Water Division: 6
• Date: 1/1/3000
• Author: Unknown
• Title: Executive Summary - Task 4 Technical Memorandum on Hydrology Water Rights and Development of Basin Model - Yampa River Basin Alternatives Feasibility Study - Draft
• Water Supply Pro - Doc Type: Report/Study

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DRAFT

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EXECUTIVE SUMMARY

Task 4 Technical Memorandum
on .
Hydrology, Water Rights, and Development of Basin Model

Yampa River Basin Alternatives Feasibility Study

Objectives of Task 4

The objectives of Task 4 were to review the hydrology and water rights structure.of the Yampa
River basin, to develop a computer model of the basin refleCting that structure and capable of simulating
future water development and management proposals, and to develop hydrologic, water rights, and
water demand data for use in the basin model. This was accomplished by carrying out several subtasks
which: 1) defined the overall modeling approach, 2) reviewed USFWS modeling used to derive the Inter.
im Flow Recommendations, 3) developed hydrologic data sets to support modeling, 4) reviewed the
water rights structure of the basin to support model development, and 5) developed and calibrated the
basin model.

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Review of USFWS Model

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The U.S. Fish and Wildlife Service applied its HYDROSS modeling system to the Yampa and
Green River basins to evaluate the hydrologic implications of operation and development of existing and
future water uses. The modeling of the Yampa River basin was used to derive the Interim Flow Recom.
mendations at Deerlodge Park for recovery of the endangered fishes. A detailed review of the USFWS
modeling work was done in order to fully understand the assumptions reflected in the flow recom.
mendations. The review included the development of a network analog of the HYDROSS model using
the same modeling syst<:m that was ultimately used to develop the basin model.

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The review identified some questionable assumptions in the HYDROSS modeling effort and
identified a few data errors in the HYDROSS Input files. The effects of these assumptions and errors are
to overestimate river depletions for some portions of the 1930 to 1982 study period and to un.
derestimate them for other portions, Overall these effects are relatively small compared to the flow of
the Yampa River; after adjustment for a few obvious errors the estimated historical river depletions are
consistent with independent estimates. Comparison or the HYDROSS assumed future depletions with
those derived in Task 2 of this study revealed that the HYDROSS values fall in between the values
projected Task 2 for years 2015 and 2040,

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Review of Basin Water Rights

A review of the water rights structure of the basin was accomplished through examination of the
State Engineer'S 1988 Water Rights Tabulation and diversion records, from discussions with staff of the
Division 6 Engineer and other knowledgeable local people, and from secondary sources. This review
identified the key water rights in the basin that needed to be represented in the basin model. These
, rights included: I) the senior calling rights of the Maybell Canal, 2) the rights, associated with the Juniper
Project, 3) the rights supporting diversions by the principal municipal and industrial water users in the
basin, and 4) the right'; supporting the operation of Stagecoach, Steamboat Lake, and Elkhead reser.
voirs. In addition, the review addressed the various subordinations of the Juniper rights to other junior