ISFAPPC04843

• Case Number: 82CW0255
• Stream Name: East River
• Watershed: East River
• Water Division: 4
• Water District: 59
• County: Gunnison
• Instream Flow App - Doc Type: Supplemental Data

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CBMR retained the services of Hydrography Resources to help monitor East River streamflows,
Beginning in 1988 and continuing to the present, Hydrography Resources has made repeated flow
measurement at the snowmaking diversion site during the fall and early winter period. Based upon
these measurements, a new stage/discharge relationship was established using a staff gage located
in the pump house for reference. However, similar to the original water stage manometer system,
the stage/discharge relationship became invalid once the ice covered the East River.

In June of 1991 CBMR engaged the services of Resource Engineering, Inc, (RESOURCE) to review
the streamgaging program and to help devise a procedure to improve streamflow monitoring during
the winter period. This report provides the results of our review,

WINTER GAGING

The continuous measurement of winter streamflow at high elevation sites is extremely difficult,
Cold temperatures and heavy snowpack combine to create icing condition similar to that
experienced by CBMR. Virtually all types of gages, whether they are water stage manometer
systems or conventional water stage recorders are subject to freezing and/or inaccuracies due to
poor stage/discharge relationships,

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Streamflow stations maintained statewide by the U,S. Geological Survey (USGS) experience similar
problems, Daily streamflows at high elevation USGS gages are most often estimated based upon
monthly streamflow measurements, Often, hydrologists must chop ice from the stream surface
to obtain a winter flow measurement, This monthly measurement provides a reasonably accurate
estimate of daily streamflows during the late fall/winter base flow period. During this time
streamflows are relatively consistent from day to day as most of the flow originates from
.gro.yndwaJer ~so.u(ces, This winter gaging procedure is similar to that currently undertaken by
CBMR.

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Due to the high elevation and remote nature of the East River gage site, it is our opinion that a
continuous streamflow monitoring station as required in the Forest Service Agreement is not
practical, The build-up of winter ice and snowpack would necessitate that the ice be chopped and
streamflow measured almost daily in order to define the changing stage/discharge relationships.
As this is not practical, an alternate procedure to calculate daily streamflows is recommended.

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