DWR_2668843 - Laserfiche WebLink

Discharge.-- PLATTE RIVER BASIN MIDDLE SAINT VRAIN AT PEACEFUL VALLEY Location.-- Drainage and Period of Record.-- Lat. 40 07’ 55”,Long. 105 31’ 00”, NE1/4 NW1/4 Sec. 24, T.2 N., R.73 W. Gage established on May 14, 1998 by State of Colorado, Division of Water Resources personnel. This gage will be a partial year record station. Graphical stage recorder, digital shaft encoder and Sutron 8210 Satellite Monitoring Data Collection Platform (DCP) in a 42-inch corrugated metal pipe shelter and 42-inch steel stilling well. The primary reference is a metal drop tape and adjustable reference point (RP) located on the equipment shelf of the shelter. No other supplemental references are available. On October 16, 2008 the Sutron 8210 DCP and Sutron 8500 SE were replaced with a Sutron Satlink 2 DCP and a Sutron 56-0540 SE. Equipment.-- Hydrographic Conditions.-- Gage-Height Record.-- Datum Corrections.-- Rating.-- Discharge.-- Special Computations.-- Remarks.-- Recommendations.-- 16.8 square miles of drainage, comprised wholly of uninhabited forested lands with varying topography. Gage is located in the Indian Peak Wilderness Area of Roosevelt National Forest, at the Peaceful Valley / Camp Dick United States Forest Service campground facilities. No known diversions occur upstream from the gage. Marked diurnal flow occurs during peak snowmelt months. Due to heavy winter conditions and the remoteness of this gage, year-round operation of the gage is not possible. The primary record is hourly averages of 15-minute telemetered data with graphical chart record as backup. The record is complete and reliable, except for the following periods: October 13-16, 22-24, 2008 and November 5-12, 2008 when the gage was affected by ice ; and, November 13, 2008 to May 10, 2009 when the gage was closed for winter and no gage- height information is available . Installation of the new DCP and shaft encoder October 16, 2008 resulted in missing data values. These values were estimated using GH data before and after the construction with consideration to ice affect as ice still remained in the channel. Artificially elevated stage values of .01 ft. to .02 ft. incurred by performing discharge measurements immediately downstream from the gage, when the Hydrographer was directly in front of the inlet. The affect is considered to be negligible to the record, but the measurement GH’s were adjusted to the correct value. Levels were run on October 16 and 31, 2008 and then again on October 14, 2009. On October 31, 2008 several new reference marks were added to the station: RM #1, RM #2, and RM #3. Levels run on October 16, 2008 were used to establish a new RP index for the gage as the instrument shelf was replaced on this date. Levels were not run prior to replacement of the instrument shelf. Therefore, the gage was assumed to be stable this year, and this assumption is supported from level history showing no movement in the base gage since 1998 when the gage was initially indexed. Levels run on October 31, 2008 were run to verify new RP index and establish additional reference marks (RM). The RP was discovered to be an average of 0.014 ft. low in elevation, no correction was made. When levels were run on October 14, 2009, the RP was discovered to be an average of 0.014 ft. low in elevation, no correction was made. The control for low to moderate stages is a rock riffle approximately 15-feet downstream of the gage composed of embedded cobble and boulders. The high water control is a sharp bend and gradient change in the stream channel approximately 40-feet downstream for the gage. The low to moderate control is subject to shifting boulders moving in to and out of the control area as well as material embedding and being released from the rock riffle. Moss and debris accumulation is not an issue at this gage. Rating No. 4 in use since October 1, 2004 was continued this year. Rating No. 4 is defined by measurements from 4.6 to 176 cubic feet per second (cfs). Twelve discharge measurements (Nos. 87-99) were performed this year ranging in discharge from 4.41 to 260 cfs. Measurements made this water year cover the range in stage except for June, 27, 2009, where mean daily GH exceeded the highest measured GH by .03 ft. of stage. The peak flow of 346 cfs occurred at 2000 on June 26, 2009 at a stage of 3.39 feet with a shift of -0.19 ft. It exceeded measurement No. 94 made on June 27, 2009 by 0.17 feet of stage. Shifting control method was used all year. Unadjusted shifts ranged from +0.01 to -0.19 feet. Shifts were distributed by time from Oct 1, 2008 to Jun 9, 2009. Shifts were distributed by stage using two variable stage-shift relationships: MIDSTECOVST01, based on Msmt. Nos. 92-94, was applied from Jun 9-27, 2009, and MIDSTECOVST02, based on Msmt Nos. 94-99, applied from Jun 27 – Sep 30, 2009. Discharge values during periods of ice effect were estimated from surrounding good record with consideration of temperature trends. This is a partial year record. No record was kept for the winter period (November 13, 2008 to May 10, 2009). Very few measurements have been made in the upper ranges in flow. The high water measurement that defines the peak was made from the downstream bridge where holiday traffic required the use of 20 second counts. The record is good except during periods when the gage was ice affected, which is estimated and fair. The instantaneous peak is rated fair due to lack of rating definition. Station maintained and record developed by Patrick Tyler. Efforts should be taken in continuation of upper end rating development as conditions allow. Peak diurnal stages and higher flow rates occur in late May to early June around 22:00 to 24:00 hrs and short in duration making rating development at high flows difficult. Levels should be run in the spring at the opening of the station to verify the discrepancy in the RP elevation. Levels should also be run annually for the next several years to verify stability of newly established reference marks. 2009Water Year