01N060 – Bertrand Creek near mouth
Technical Notes: 2008 Water Year
Chuck Springer

The telemetered stream gaging station on Bertrand Creek near the mouth operated throughout 
Water Year (WY) 2008 without interruption.  During this time, ten discharge measurements were 
made and 19 discrete manual stage readings were taken at this station.  Cumulative potential 
error for this station for WY 2007 was ±23%.

Rating Curve

This station began WY 2008 in transition from Rating Table 12 to Table 7 (see WY 2007 
technical notes for a description of Table 12).  Table 7 covers a range of discharge from 1.1 cubic 
feet per second (cfs) to 1,260 cfs.  Three of the 16 discharge measurements used to develop this 
rating were taken during WY 2008.  The measured flows for this rating, ranging from 2.2 to 633 
cfs, covers only 50% of the rating curve; however, flows exceeded the highest measured flows 
only 1% of the time that Table 7 was in effect during WY 2008.  Flows greater than 633 cfs were 
extrapolated using a log offset (e = 1.3) to temporarily straighten the rating curve in log space.
 
A large storm event in December 2007 caused a small amount of scouring on the sand banks at 
this station shifting the mid-range of the rating curve slightly.  This shift is reflected by Table 8.  
Since high and low flows were not affected by this fill on the banks, statistics cited above for 
Table 7 also apply to Table 8.  Six of the 15 discharge measurements used to develop this rating 
were taken during WY 2008.

A moderate storm event in August 2008 caused a fill of the low end of the rating curve, which is 
represented by Table 9.  Table 9 covers a range of discharge from 0 to 1,260 cfs.  Five of the 16 
discharge measurements used to develop this rating were taken during WY 2008.  The measured 
flows for this rating, ranging from 18.5 to 633 cfs, covers less than 50% of the rating curve.  
Flows exceeded the lowest measured flows 80% of the time that Table 9 was in effect during 
WY 2008.  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 WY 2008 for this 
station is ±18%.

Stage Record

The station logged continuously throughout WY 2008 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 differed from manual staff gage readings by variable amounts, 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.