DWR_2668843

• Title: STREAM FLOW DATA FOR COLORADO
• Year: 2009
• Document Type - Publications and Reports: Streamflow Report

Discharge.--
PLATTE RIVER BASIN
06694920 SOUTH PLATTE RIVER ABOVE SPINNEY RESERVOIR
Location.--
Drainage and Period of Record.--
Lat. 38°59'10",Long. 105°40'52" in NE1/4 Sec 21, T. 12S, R. 74W, Park County, 3.3 miles below the confluence of the Middle
and South Forks of the South Platte River, and 7 miles southeast of Hartsel, CO.
772 square miles. October 1982 to present.
Stevens A-71 graphic water-stage recorder and Sutron SatLink 2 satellite Data Collection Platform (DCP) with a Sutron 56-
0540 shaft encoder (SE) at a 25-foot concrete Parshall flume. The equipment is in a wooden shelter over a concrete well
with inside electric tape gage and a staff gage on the left side at the Ha location. The gage and satellite monitoring
equipment are owned and maintained by the City of Aurora. Aurora operates the gage seasonally and is shut down in the
winter. Colorado Division of Water Resources (DWR) operates the gage for records and is paid by Aurora to provide real
time data.
Equipment.--
Hydrographic Conditions.--
Gage-Height Record.--
Datum Corrections.--
Rating.--
Discharge.--
Special Computations.--
Remarks.--
Recommendations.--
Flows at the gage are affected by releases from Antero Reservoir and natural flows from the South and Middle Fork of the
South Platte River.
The primary record is hourly averages of 15 minute data satellite data with chart back up. The primary record agrees with
the chart to within +/-0.02 ft. The record is complete and reliable except as follows: November 7, 2008 to April 7, 2009,
when the gage was shut down for winter. October 22, 23, 24; and November 5, 6; when stage discharge relationship was
affected by ice. On four days hourly values were compromised by flushing of the intakes. On site observation along with
good chart data was used to fill in missing data without loss of accuracy. Thirty six visits were made to the gage. Two
shaft encoder calibrations adjustments were necessary.
Levels were run on August 27, 2008. The gage was found to be reading within the ±.02 ft. tolerances. No corrections were
made.
The control is a 25-foot Parshall flume with a standard rating. Negative shifting can be caused by moss growth; however
this year significant moss growth was not observed. Positive shifting is possibly caused by the approach conditions. High
flows have been observed to by-pass the flume by leaving the channel and crossing the access road. This is believed to
occur at gage heights greater 4.35 ft. and flows in the 1000 cfs range. The rating is well defined to 466 cfs by
measurements made since 2001. Wading measurements are made downstream of the foot bridge (section width 30.5 ft)
while section rod and cable measurements are made on upstream side (section width 32.1 ft). Bridge is indexed on both
sides to obtain accurate section widths. Thirteen measurements (Nos. 276 - 288) were made during the water year, ranging
in discharge from 36.2 to 466 cfs. They cover the range in discharge except for many days with lower mean daily flows and
higher daily flows on June 2 and June 28, 2009. Peak flow of 506 cfs was recorded at 0315 June 2, 2009 at a gage height
of 2.78 ft. and using a stage-distributed shift of +0.07 ft. The peak exceeded the stage of measurement No. 281 made
May 27, 2009 by 0.14 ft. Using the "Water Measurement Manual" U.S. Department of the Interior Bureau of Reclamation
Third Edition, Figure 8-9, Page 8-44. A 25' Parshall Flume's range of accurately measuring discharge is 15 cubic feet per
second to 1200 cubic feet per second. Anything above or below this range is outside the +/- 5% accuracy. All flows during
the 2009 water year were within this range during the operational period of the gage.
Stage dependent shifting was used for water year. Two variable shift tables were utilized for the record with the exception
of winter estimated periods. PLASPICOVST1 was used from the start of the year to measurement number 284 made on
July 13, 2009 when discharge declined from the peak when the approach to the flume appears to have been scoured
reducing shifting for the remainder of the year. PLASPICOVST2 was applied from measurement 284 to the end of the year
to account for the channel changes. Measurements 278 and 280 were adjusted 3% and 1%, respectively, to fit the stage-
shift relationship.
Estimates were made as follows: November 7, 2008 to April 7, 2009, when the gage was shut down for winter. Daily
discharge for this period was estimated using Aurora’s accounting. October 22, 23, 24, 2008 ice estimation using adjacent
periods of good record. November 5, 6, 2008 ice estimation using adjacent periods of good record. During the period
when estimates were taken from Aurora’s Spinney Mountain Reservoir accounting, the estiamtes are based on reservoir
elevation readings, and tend to show step-wise changes. The frequency of the reservoir elevations readings is daily;
however surface ice on the reservoir affects the readings, so the accuracy of daily discharges is questionable.
The record is good, except for the following periods which are estimated and poor: November 7, 2008 to April 7, 2009,
when the gage was shut down for winter; and days of ice-affect: October 22, 23, 24, 2008; November 5, 6, 2008; and April
18, 2009. Record developed by Mike Wild.
None.
2009Water Year