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Discharge.-- PLATTE RIVER BASIN 06711500 BEAR CREEK AT SHERIDAN Location.-- Drainage and Period of Record.-- Lat. 39°39'08",Long. 105°01'57", in NW¼NW¼ sec. 5, T,5 S., R.68 W., Arapahoe County, Hydrologic Unit 10190002 on left bank just downstream from bridge on South Lowell Blvd., at Highway Department maintenance building at northwest city limits of Sheridan, 1.3 mi upstream from mouth, and 2.l mi west of city hall in Englewood. 260 mi². April to Nov. 1914, March 1927 to current year. Monthly data only prior to Oct. 1933. Stevens A-35 graphic stage recorder was removed this year, and Sutron 8210 DCP with digital shaft encoder and phone (speech card) modem in a 42 inch corrugated metal shelter and well with supplemental outside wire weight gage remains. The wire weight gage was damaged by vandalism and has not been repaired. No outside readings were made during the 2009 water year. The DCP can be accessed by phone. Currently, no backup to the shaft encoder is present. Equipment.-- Hydrographic Conditions.-- Gage-Height Record.-- Datum Corrections.-- Rating.-- Discharge.-- Special Computations.-- Remarks.-- Recommendations.-- Flows are controlled by releases from Bear Creek Lake, approximately 6 miles upstream. The land between the gage and the Lake is urban, and sharp peaks are observed as a result of storm runoff. The gage is directly affected by local precipitation since there is a large storm culvert just upstream which drains a large shopping center. The peak flow usually occurs as a sharp, short-duration storm event. The primary record is hourly averaged 15-minute data from satellite with partial year chart back-up. The record is complete and reliable for the entire year, except for a few hours each day on Nov. 23, 2008 and May 14, 2009,and from May 14- Sept. 30, 2009 one 15 min value at 18:00 was missing on each day. The Nov. data was taken from the chart, and all other data was estimated. Possible ice effect was seen on November 26 and December 15. Ice affect was seen on December 21-22, 2008. Corrections were made after clearing debris from the control (which results in a drop in gage height). Corrections in gage height as a result of debris on the control were applied as follows: Oct 2, 2008: -0.03 ft, applied to 0000 Oct. 1 to 1500 October 2. November 13, 2008: -0.03 ft, manually applied back to a high water event on October 5, 2100 that most likely deposited the debris. April 24, 2009, -0.07 ft, applied back to a high water event on April 18 that most likely deposited the debris. The inlets were flushed almost every visit in an attempt to keep the inlets clean and eliminate any flush corrections. Two such flush corrections were necessary and applied: June 17, +0.04 ft applied back a couple of hours to a low point in the hydrograph where the pipe most likely plugged up, and June 29, +0.03 ft applied back one hour to a low point on the hydrograph, where the pipe most likely plugged up. Levels were last run on July 26, 2006. No correction were necessary. The control for all stages is a rock and concrete dam approximately ten feet below the gage with about 5 ft. of drop behind it. Downstream conditions have never been observed to cause backwater at the gage. The dam has an uneven surface, with rebar sticking out in spots. Debris tends to accumulate at low flows, particularly in the fall when leaves are dropping. Rating No. 32 was developed for the 1998 water year, and continued in use for the present year. It is defined by measurements to 661 cfs.. In past years the gage has experienced short peaks well above the rating , so the rating has been extrapolated to 3000 cfs. However, any flows above 1000 cfs need to be considered estimates. Nineteen measurements (Nos. 953 - 971) were made this year ranging in discharge from 6.16 to 147 cfs. They cover the range in discharge experienced except for days with lower mean daily flows on Nov 11, Dec 6, and Apr 15; and hogher mean daily flows on April 25-29, May 1-3, and 25-27, June 2-6, and 26, 2009. The peak flow of 795 cfs occurred at 2145 on Jul 25, 2009 at a gage-height of 4.96 feet with a shift of 0.00 feet. It peak exceeded measurement No. 962 (made on April 29, 2009), by 1.65 ft. in stage. Shifting control method was used for the record year. Shifts were caused by scour and fill of the approach pool and material passing over the control. Shifts were distributed by time with consideration to stage for the entire water year. Measurements show shifts varying from –0.02 to + 0.01 ft. Shifts were distributed by time. All measurements were given full weight except for Nos. 957, 960, 963, 965, and 970 which were adjusted up to 4% to smooth distribution. Consideration to stage was given between No 961 (4/16) and No. 962 (4/29) by using the event peak on 4/18 as a distribution point. Consideration to stage was given between No 967 (7/22) and No. 968 (8/05) by using the yearly peak flow event on 7/25 as a distribution point. Flow conditions are relatively steady year-round and fluctuate little from rain events. The majority of flow represents a controlled release from Bear Creek Lake approximately 6 miles upstream. This steady flow allows for reasonable assumptions to be made during periods of estimated record. Computed record was used for possible ice affect days of November 26 and December 15. December 21- 22 were estimated from temperatures and adjacent good record. The record is rated as good, except for periods of possible ice effect, which are fair and periods of ice effect, which are estimated and poor. Station maintained and record developed by Jana Ash. Continue visits every two weeks to ensure the control stays clear of debris, especially after rain events. The wire weight gage needs to be replaced or a staff pounded into the streambed. If possible, extra visits should be made during extreme cold to break ice in the well. Light construction should be done to remove the catch points on the control to help with debris affecting gage height. The rating above 1000 cfs needs to be confirmed by slope-area or some other indirect method. 2009Water Year