WSP10841

• File Number: 8200.760
• Description: Yampa River General
• State: CO
• Basin: Yampa/White
• Water Division: 6
• Date: 1/1/1993
• Author: Hydroshpere
• Title: Yampa River Basin Alternatives Feasibility Study - Executive Summary - Draft - January 1993
• Water Supply Pro - Doc Type: Report/Study

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000438

Executive Summary

allow additional upstream junior diversions. The amount of water that could be exchanged out
of the Williams Fork Reservoir was limited in the model by imposing a minimum instream
flow to prevent the Yampa River from being dried up in some occupied habitat reaches
(specifically the mainstem above the Williams Fork) during the months of August and
September. The amount of this minimum instream flow constraint was suggested by the
USFWS and represented in the model as 150 cfs in August and 110 cfs in September. There
were no such constraints on exchange potential in other months.

Shortages occurring in Scenario V for the existing senior demands were identical to
those observed in Scenarios I through IV. Shortages to existing junior demands and to future
demands were higher than in Scenario IV but substantially smaller than Scenario m. Modeled
shortages under Scenario V are summarized in Table S-5.

Williams Fork Reservoir remained relatively full over the study period and on only two
occasions briefly dropped below 60,000 af. The potential to exchange water up the Yampa
River was occasionally limited by either the natural flows or the minimum flow constraints
specified in the model. This placed more burden on Elkhead Reservoir to meet the Craig area
demands than occurred in Scenario IV. The result was an increase in the draw on Elkhead
over that of Scenario IV and greater fluctuations in storage levels than in Scenario IV.

Table S-5
Summary of Modeled Demand Shortages
Over 53 Year Study Period
Demand Catel!orv Scenario I . Scenario II Scenario III Scenario IV Scenario V
Potential 1989
Maximum 7,782 4,026 5,841 822 3,379
Average 312 4,062 1,955 40 700
Projected 2015
Maximum. 2,037 3,587 572 0 1,595
Average 50 455 129 0 42
Projected 2040
Maximum 9,242 28,220 15,685 5,807 5,518
Average 537 11,031 4,385 180 803

Notes: ] - Sum of maximum annual shortages for all demands in category.
2 - Average annual shortage to all demands in category.

Environmental Considerations

Instream Flows

An important aspect in formulating near and long term water development projects and
strategies as part of the Feasibility Study was the consideration of fisheries and other wildlife.
Of particular concern were stream flows predicted for the Yampa River mainstem in occupied
habitat areas of the Threatened and Endangered species. The modeled effect of administration
of the Juniper Project contemplated draft, as converted to an instream flow right at Juniper

S-17

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