01C070 – Hutchinson Cr. nr Acme
Technical Notes:  2005 Water Year 
Chuck Springer

The telemetered streamgaging station on Hutchinson Creek near Acme operated 
throughout water year 2004.  A series of storm events in October and November caused 
fairly extensive flooding in the Nooksack basin, mainly in the agricultural lowlands.  At 
this station, even though these events resulted in the highest peak discharge in the 
station’s two and a half years of record, they did not cause any noticeable changes in 
channel geometry or in the relationship between stage and discharge.  A large rain-on-
snow event in mid-January effectively marked the beginning of spring snowmelt.  
However, abundant spring rainfall kept flows from dropping dramatically until mid-July.  
Despite abundant rainfall through the spring and early-summer, minimum summer flow 
was 4.5 cfs in September 2005; nearly 15% lower than in the previous two water years of 
record.

Rating Curve
The rating curve for the station covers a range of discharge from 3.4 cfs to 690 cfs. The 
range of stage encountered during the water year was 4.1 feet.  The range of discharge 
encountered during the water year was from 4.5 cfs in September 2005 to 686 cfs in 
November 2004.  The measured discharge, ranging from 4.2 cfs to 121 cfs covers only 
17% of the magnitude of flows encountered during the water year  .  However, flows 
exceeded the rating curve only 8% of the time.  All low flows encountered during the 
water year were within the measured range.  Flows greater than 121 cfs were modeled 
using the established relationship between stage and velocity during the highest measured 
flows, along with a surveyed high cross-section.  The accuracy of flows derived from this 
model is estimated to be within 15%.

Stage Record
The station logged continuously throughout water year 2005 without interruption.  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, but was as high as 0.16 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.

Future Efforts
Storm event flow measurements are needed at this site to augment the upper range of the 
rating curve.  Also, mid-range flow measurements are needed between 1.5 feet and 
1.9feet of river stage.  A re-survey of the high flow cross-section will be conducted in 
summer 2006.

cws