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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. A Sutron 8210 DCP with digital shaft encoder and phone (speech card) modem in a 42 inch corrugated metal shelter and well. Primary reference is an Electric Drop Tape (ETG). The wire weight gage was damaged by vandalism and has not been repaired. No outside readings were made during the 2010 water year. The DCP can be accessed by phone. A backup encoder was installed Dec 16, 2009 as no backup recorder was in place after removal of the A-35 recorder in WY09. The primary shafte encoder was replaced on Jan 6, 2010. Equipment.-- Hydrologic 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 are now two large storm culverts just upstream, another storm drain was added in July of this year which drains a local ball park south of the gaging station. A large shopping center is drained by the storm culvert on the north side of Bear Creek. The peak flow usually occurs as a sharp, short-duration storm event. Flow conditions are relatively steady year-round. The majority of flow represents a controlled release from Bear Creek Lake. This steady flow allows for reasonable assumptions to be made during periods of estimated record. The primary record is hourly averages of 15-minute data from satellite. Record is complete and reliable for the entire year, except for the period of December 26, 2009 through January 6, 2010, when the shaft encoder failed and produced flat-line data; and the periods December 9 and 10, 2009, and February 23, 2010 when ice affected the stage discharge relationship. A gage height correction of +0.02 ft was made February 2, 2010. Corrections in gage height made as a result of cleaning debris off the control were applied as follows: April 7, 2010, -0.01 ft drop in GH occurred after removing a large log from the control. This was applied to March 31, 2010 where a sharp rise was observed in gage height where the log likely was deposited at the control. The inlets were flushed most visits in an attempt to keep the inlets clean and eliminate any flush corrections. A small flush correction of less than 0.01 ft was found on May 3, 2010, but not applied to the record. Levels were last run on July 26, 2006. No corrections were made. The control for all stages is a rock and concrete dam approximately ten feet below the gage with about 5 ft. of drop below 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, developed in 1998 was used 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 and poor. Eighteen measurements (Nos. 972 - 989) were made this year ranging in discharge from 11.1 to 227 cfs. They cover the flow range experienced except for: April 23-30, May 15, September 11-22, 29 and 30, 2010. The peak flow of 599 cfs occurred at 1515 on April 23, 2010 at a gage height of 4.59 ft.with a shift of 0.00 ft. It exceeded measurement No. 982 (made on May 19, 2010), by 0.96 ft. in stage. Shifting control method was used all year. Shifts were caused by scour and fill of the approach pool and material passing over the control. Shifting probably has also been affected by the addition of gravel material introduced during the construction of the storm water culvert on the south side of the channel upstream of the gage. Shifts were distributed by time with consideration to stage for the entire water year. Measurements show shifts varying from –0.03 to + 0.01 ft. All measurements were given full weight except for Nos. 981, 984, and 989, which were adjusted up to 5% to smooth distribution. Measurement Nos. 979 and 980 were adjusted to the same shift as they were made during the same visit. Flows were estimated during periods of ice affect on December 9-10, and February 23 using temperature data and adjacent good record. The period December 26 – January 6 was estimated due to missing encoder data. Flow was estimated by straight line interpretation between adjacent good record. The record is rated good, except for periods of ice effect and missing encoder data, which are estimated and considered fair. Station maintained by Jana Ash and Tony Arnett and record developed by Tony Arnett. Continue visits every two weeks to ensure the control stays clear of debris, especially after rain events. 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. Levels should be run as that has not been done since 2006. Pictures should also be taken of the interior of the gage since new equipment installation. Rating above 1000 cfs needs to be confirmed by slope-area or some other indirect method. 2010Water Year