WSP06521

• File Number: 8111.831
• Description: Arkansas River Compact Administration - Article VIII ‎(H)‎ Investigations
• Basin: Arkansas
• Date: 1/1/1985
• Author: David Pope
• Title: Supplement Report to ARCA Regarding Article VIII ‎(H)‎
• Water Supply Pro - Doc Type: Publication

City a~d Las Animas stream gages and is not reflected by the

adjusted Canon City records used in the mass diagram analy-

sis. The magnitude of these transmountain return flows is

believed to be equivalent to nearly half of the average

annual flow of the Arkansas River measured at Las Animas.

The continued existence of these return flows in the

Arkansas River is not guaranteed because users of transmoun~

tain water are entitled under Colorado water law to reuse

and completely consume transmountain diversions; whether the

users of transmountain return flows along the Arkansas River

are so entitled under interstate law is not controlled by

Colorado law. Pursuant to Colorado law, the Cities of

Colorado Springs and Pueblo currently have applications

pending in Colorado Water Court for approval of a reuse and

exchange plan involving large quantities of transmountain

return flows. If transmountain return flows are not main-

tained, the future available supply for downstream users on

the Arkansas River would decrease significantly. This

decrease in supply would reduce the quantities available for

conservation storage in John Martin Reservoir and usable

state line flows.

It is obvious that transmountain return flows have

affected streamflows, particularly above John Martin

Reservoir. Accordingly, it is equally obvious that de-

pletions of flow above John Martin Reservoir are being

masked by transmountain return flows. It is unreasonable to

assume that transmountain return flows have no impact on

streamflows or to discount their existence as Colorado has

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