WSP10461

• File Number: 8111.808
• Description: Arkansas River Compact Administration - Transit Loss
• Basin: Arkansas
• Date: 1/1/1978
• Author: USGS
• Title: Transit Losses and Traveltimes of Reservoir Releases Along the Arkansas River from Pueblo Reservoir to John Martin Reservoir. Southeastern Colorado
• Water Supply Pro - Doc Type: Publication

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Antecedent Streamflow and Stage-Discharge Relations

The flow of the upper Arkansas River is fairly uniform and predictable;
therefore, antecedent subreach' streamflow in the original model was estimated
from flow at index stations. Streamflows at the upstream and downstream ends
(nodes) of a subreach downstream from Pueblo Reservoir are frequently very
different and unpredictable. As a result, the original computer model was
modified to require antecedent streamflow as input at all nodes.

The computer model also requires stage-discharge information at both
ends of each subreach. In order to add flexibility to the model and to
recognize that individual ratings at gaging stations may not be
representative of an entire subreach, average stage-discharge relations were
used in the individual modified computer model. For example, the individual
ratings for both the gages above Pueblo and near Avondale were combined into
a single average relation that was used for both of those nodes. In the same
manner, average stage-discharge relations were developed from ratings for the
gages near Nepesta and at Catlin Dam, and for the gages at La Junta, at Las
Animas, and below John Martin Reservoir. The resulting relations used for
the seven nodes in the model are shown in table 2.

Inadvertent Diversions and Traveltime

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Those parts of the original computer model dealing with inadvertent
diversions and traveltime were removed from the modified version of the
model. Due to the types of diversion structures in the study reach,
inadvertent diversions are not a significant source of transit loss. Rather
than being estimated with theoretical relationships, traveltime Information
was derived from historic data, as discussed in a later section of this
report.

Determination of Aquifer and River-Channel Characteristics

The hydrologic model used in this study requires values for several
aquifer and river-channel characteristics that are described in detail by
Luckey and Livingston (1975). These characteristics are aquifer transmissiv-
ity, aquifer-storage coefficient, channel-storage coefficient, and length of
alluvium. The model also requires the length of river for evaporation
accounting purposes. These data (table 3) were determined for each subreach
based on previous ground-water investigations in the Arkansas River valley
(Jenkins, 1968; Major, Hurr, and Moore, 1970; Hurr and Moore, 1972; Konikow
and Bredehoeft, 1974; Taylor and Luckey, 1974), on channel configuration
shown on the most recent topographic maps, and on analysis of preliminary
model results.

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