01C070 – Hutchinson Creek near Acme
Technical Notes:  2006 Water Year 
Chuck Springer

The telemetered stream gaging station on Hutchinson Creek near Acme operated 
throughout water year 2006, with only one major interruption (see “Stage Record” 
section below).  A large storm event in January 2006 caused channel fill at this station, 
altering the stage-discharge relationship and shifting the rating curve.  Interestingly, this 
event was much smaller in magnitude than events during the previous two years of 
record; however it was the first event to change the stage-discharge relationship since the 
onset of data collection.  Minimum summer flow for this station was 4.4 cubic feet per 
second (cfs) in late-August, which is consistent with previous years of record.

Rating Curve

Water year 2006 started with Rating Table 1.  This rating curve covers a range of 
discharge from 4.0 cfs to 635 cfs. The range of stage encountered during the water year 
was 2.75 feet.  The range of discharge encountered during the water year was from 4.4 
cfs in August 2006 to 319 cfs in January 2006.  The measured discharge, ranging from 
4.2 cfs to 140 cfs covers only 43% of the magnitude of flows encountered during the 
water year.  However, flows exceeded the highest measured flow only 6% of the time.  
All low flows encountered during the water year were within the measured range.  Flows 
greater than 140 cfs were modeled using Manning’s equation to estimate velocities based 
on channel geometry and energy slope, along with a surveyed high flow cross-section.  
The accuracy of flows derived from this model is estimated to be within 25%.

Stage Record

The station logged continuously for most of water year 2006.  The battery for the station 
died on January 23, 2006, and was not replaced until February 8, 2006.  Data from 
01F070 S.F. Nooksack River at Potter Road correlated well with this station (r2 = 0.87), 
and was used to estimate the continuous record of stage during this period.  A linear 
equation was applied to the individual stage values (y = 0.443x – 1.508) to adjust the 
magnitude of the stage values and the amplitude of storm events and diurnal variations 
based on the relationship between the two stations.  The resulting data values were then 
further adjusted to manual stage readings taken on January 26, 30, February 7, and 8, 
2006.  The flow in the stream channel at this site is fairly laminar at the terminal end of 
the orifice pipe.  However, the station seems to be prone to gradual instrument drift, 
which is measured as the difference between logged and measured stage values.  Drift at 
this site usually ranged between 0.01 and 0.04 feet.  Time-weighted corrective 
adjustments were made to the continuous stage record whenever the difference between 
logged and measured stage values resulted in a 5% or more difference in discharge.  All 
adjustments are documented in the Hydstra Data Workbench.  From mid-November 2005 
to mid-January 2006 the continuous data at this site was unusually noisy.  This noise in 
the data was likely caused by woody debris that became temporarily lodged against the 
slant pipe, creating turbulence.  The decision was made not to smooth or flag data during 
this time period, since the mean daily discharge values should still be accurate.

Future Efforts

High flow measurements (>140 cfs) are needed at this site.  Also, the lower staff gage 
was bent slightly downstream during winter storm events.  This staff gage will need to be 
straightened and re-surveyed.