BOARD00154 ‎(2)‎

• Board Meeting Date: 3/13/2007
• Description: ISF Section - Notice of 2008 Instream Flow Recommendations and Summary of ISF Workshop
• Board Meetings - Doc Type: Memo

Hydrologic Data
Discharge in Arapaho Creek was estimated from gage data collected from USGS gage
09016500 (Fig. 1) aelial apportionment.IAlthough the watershed area above USGS gage
09016500 is approximately 46.9 square miles, only 17.39 square miles lie above the
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Buchanan Creek. Thus, flows through the reach above Buchanan Creek are expected to
be 0.37 that ofthose measured at the usbs gage. This aerial apportionment approach
was used to estimate daily discharge ratJs above the diversion for each day of the period
of record. I .
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Estimates of the daily discharge rates ab6ve Buchanan Creek from 10/1/44 - 9/30/71
were used to calculate the average dischkrge for each day of the year (Fig 2) as well as
the average, minimum and maximum d~ily discharge rate for each month (Table 1).
These data were then used to estimate t~e percentage of days a given flow was exceeded.
These data indicate that, throughout the ;year, the recommended flow was exceeded by 50
percent of observed daily discharges (T~ble I).

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The United State Geological Survey's StreamStats tool was used generate estimates of
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average monthly flows in Arapaho Creek (Table 2). StreamStats can be found at:
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htto:/ /watcr. USgS.gov /osw/streamstats/ colorado. html

StreamStats uses regression equations to provide estimates of discharge for ungaged sites.
This analysis also indicated that througHout the year typical flows through the watershed
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would exceed the recommended flows.

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Precipitation Data
Local climate data from the Grand Lake weather station have also been attached
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(Appendix C).

Existing Water Right Information
At one time or another, three structures held water rights in the Arapaho Creek watershed
that potentially could have impacted ins~eam flows along Arapaho Creek. The Arapaho
Creek Ditch (Structure ID Number: 511~ and the Arapahoe (sic) Ditch and Tunnel
System (Structure ID Number: 992) wefe both located along the main stem of Arapaho
Creek while the Divide Ditch No 2 (Stnicture ID Number: 997) was located along Mill
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Creek, a tributary to Arapaho Creek (Fig I). The water rights for three of these
structures, however, have been abandoned. The Arapaho Creek Ditch rights were
abandoned in 1984, the Arapahoe Creek Ditch and Tunnel System rights were abandoned
in 1980 and the Divide Ditch No 2 rights were abandoned in 1981. For a more complete
description of these structures see the fdllowing Structure Summary Reports.
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