WSP09785

• File Number: 8142.600.30.A
• Description: Trinidad Project - Studies - Other Studies - Purgatoire river transit loss study
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 1/1/1993
• Author: USGS
• Title: Evaluation of Streamflow Traveltime and Streamflow Gains and Losses Along the Lower Purgatoire River Southeastern Colorado 1984-1992
• Water Supply Pro - Doc Type: Report/Study

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0 DAILY ANALYSIS (J @
II STREAMFLOW. * ~
EVENT ANALYSIS *
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Figure 11. Boxplots showing daily mean streamflow gains and losses and daily mean streamflow-event
gains and losses for reach 3 of the study area, 1984-92. :

CONFIDENCE IN ACCURACY
OF ESTIMATES

Overall confidence in the estimation of stream-
flow traveltimes and of streamflow gains and losses
using historical streamflow and diversion records was
considered to be good to fair for reaches 2 and 3,
which compose about 100 mi of the lower Purgatoire
River. Because available information was insufficient
to quantify the return flows and other tributary contri-
butions (ungaged inflows) in reach 3, the magnitude of
errors in assuming that ungaged streamflow in an
irrigated river reach generally was inconsequential
could not be evaluated directly. The streamflow-event
analyses that were made for reaches 2 and 3 did help
to strengthen the confidence ih the accuracy of the
reported estimates of streamflow gains and losses for
these two reaches.
The hydrologic data available for reach I did
not provide adequate information to estimate stream-
flow traveltime and to determine streamflow gains and

josses accurately. Additional information that could
Improve confidence in traveltime estimates and
quantify streamflow gains and losses for specific flow
conditions better include:

,1. Dye-tracer studies conducted dnring two or more
. flows, preferably a low flow and a high flow, to
determine traveltimes for the transport of stream-
I flows to downstream river locations.
I
~. Identification and quantification of ungaged inflows
! to the lower Purgatoire River system, including
the extent of operational practices by canals
(sluicing); the surface routing of irrigation field
tailwater, waste flows, and other sources of return
flows; and the magnitude of streamflow contribu-
tions by tributary streams.
I
i Determination of streamflow traveltime and
petter estimates of streamflow gains and losses
in a complex irrigated surface-water and ground-
'water system, such as in the lower Purgatoire
River, conld be approximated by the nse of computer

22 Evaluation of Streamflow Traveltime and Streamflow Gains and Losses along the Lower Purgatoire River, .
Southeastern Colorado, 1984-92 I
!
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