01N060 – Bertrand Creek near mouth
Technical Notes: 2010 Water Year
Chuck Springer

The telemetered stream gaging station on Bertrand Creek near the mouth operated throughout 
Water Year (WY) 2010 without interruption.  During this time, eight discharge measurements 
were made and no additional discrete manual stage readings were taken at this station.  
Cumulative potential error for this station for water year 2007 was ±21%.


Rating Curve

This station began WY 2010 on Rating Table 101.  Table 101 covers a range of discharge from 0 
to 112 cfs.  Three of the 12 discharge measurements used to develop this rating were taken 
during WY 2010.  The measured flows for this rating, ranging from 0 to 56 cfs, cover only 50% 
of the rating curve.  However, flows exceeded the highest measured flows only 1% of the time 
during the two months Table 101 was in effect during fall 2009.  Flows between 56 and 112 cfs 
were extrapolated using a log offset (e = 1.4) to temporarily straighten the rating curve in log 
space.  Since this rating table had high flows that were unique from any other rating for this 
station and the rating occurred during two distinct and relatively short time periods, the field 
survey data to support a high flow modeling effort could be collected.  Thus flows greater than 
112 cfs (twice the highest measured flow) are not reported.
 
In November 2009, a series of storm events partially washed away the debris pileup downstream 
of the gaging station, effectively “scouring” the channel control segment of the rating curve.  
This shift is represented by Table 11.  Three of the nine discharge measurements used to develop 
this rating were taken during water year 2010.  Table 11 covers a range of discharge from 0 to 
630 cfs.  The measured flows for this rating ranging from 0 to 314 cfs cover only 50% of the 
rating curve.  However, flows exceeded the highest measured flows only 3% of the time during 
the month Table 10 was in effect during winter 2010.  Flows greater than 314 cfs were 
extrapolated using a log offset (e = 1.4) to temporarily straighten the rating curve in log space.

Sometime between January and March 2010, the remainder of the debris pileup downstream of 
the gaging station washed away, further scouring the channel control segment of the rating curve.  
This shift is represented by Table 12.  A total of five of the 15 discharge measurements used to 
develop this rating were taken during WY 2010.  Table 12 covers a range of discharge from 0 to 
1,260 cfs.  The measured flows for this rating ranging from 0 cfs to 633 cfs, covers only 50% of 
the rating curve.  However, flows did not exceed the measured range of flows during the nine 
months that Table 9 was in effect during WY 2010.  Flows greater than 633 cfs were 
extrapolated using a log offset (e = 1.1) to temporarily straighten the rating curve in log space.

The calculated potential error for flows derived from rating curves used during water year 2010 
for this station is ±14%.



Stage Record

The station logged continuously throughout WY 2010 without interruption.  The staff gage at 
this site is generally readable to within 0.02 ft throughout the range of flows.  Conditions 
surrounding the terminal end of the bubbler orifice are similar to those around the staff gage.  
The stage height readings typically differed from manual staff gage readings by 0.04-0.07 ft, but 
by as much as 0.15 ft.  Time-weighted corrective adjustments were made to the continuous stage 
record whenever the logged and measured stage values differed.  All adjustments are 
documented in the Hydstra Data Workbench.

The calculated potential error of the continuous stage data for this station is ±6%.

Future Efforts

This station experiences frequent rating shifts.  Ongoing frequent discharge measurements are 
necessary at this station to ensure accuracy.