WSP12668

• File Number: 8230.400.30.F
• Description: Durango RICD - Other Reports
• State: CO
• Basin: Colorado Mainstem
• Water Division: 7
• Date: 3/1/2006
• Author: W. W. Wheeler and Associates
• Title: City of Durango Boating Park Hydrology Study
• Water Supply Pro - Doc Type: Report/Study

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1928 through 2004. This 77-year period is representative of ttie long-term conditions in
the Animas River Basin, covering wet, average, and dry periods.

Daily streamflow records at the Lightner Creek gage were published from 1928
through 1949. We have estimated the daily Lightner Creek streamflow during the period
from 1950 through 2004 using the following procedure:

1) For each month during 1928 through 1949, the total Lightner Creek and Animas
River streamflow volumes were calculated. Monthly ratios of Lightner Creek
gage streamflow to Animas River gage streamflow were determined.

2) For the 1950 through 2004 period, the daily Lightner Creek streamflow was
calculated by applying the applicable monthly ratio to the daily Animas River
gage streamflow.

Daily Calculations
By comparing the daily streamflow with the RICD appropriation amounts for
Structures 5 and 9, the number of days in each month (of the 1928 through 2004 study
period) when the flow of the Animas River at the Boating Park equaled or exceeded the
RICD flows was determined. In addition, 1) the available streamflow claimed by the
RICD and 2) the streamflow surplus to the RICD claims were calculated for each month
of the study period. The number of exceeded days is included in Table 1. The
streamflow claimed by the RICD for Structures 5 and 9 is summarized in Table 2 and the
surplus streamflow is summarized in Table 3. As shown in these tables, adequate
streamflow was available to satisfy the proposed RICD appropriation for at least a
portion of most months in the study period. During dry-years such as 2002, there are
extended periods during which the streamflow is less than the RICD claims.

Over the 1928 through 2004 study period, the maximum claimed RICD flows for
Structures 5 and 9 have been satisfied an average of 267 days per year. In other words,
the RICD flows have been satisfied an average of 73 percent of the days in a year.

During those periods when the RICD flows for Structures 5 and 9 are not
satisfied, the City of Durango will place a call on the Animas River for the curtailment of

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