01G100 – M.F. Nooksack R. above Clearwater Cr.
Technical Notes:  2006 Water Year
Chuck Springer

The instantaneous stream gaging station on the Middle Fork Nooksack River above 
Clearwater Creek was monitored throughout water year 2006.  During the water year, 
three discharge measurements were made and 28 instantaneous stage readings were taken 
at this station.

Rating Curve

This station started water year 2006 amid a phased, or prorated, shift from rating Table 3 
to rating Table 4.  This minor shift was caused by channel fill that occurred sometime 
during a series of large storm events between late September and mid-November 2005.  
During these storm events, tree fall near one side of the channel caused bed material to 
accumulate, elevating the stage height at moderate flow levels.  Since the thalweg was 
unaffected, low flows remained the same.

From mid-November to the end of the water year, the station operated under rating  
Table 4.  This rating table covers a range of discharge from 75 cubic feet per second (cfs) 
to 4,300 cfs.  Three of the seven discharge measurements used to develop this rating were 
taken during water year 2006.  The measured flows for this rating, ranging from 150 cfs 
to 1,300 cfs, cover only 27% of the rating curve.  However, discharge exceeded the rating 
curve only 4% of the time during the water year.  Two percent of flows are below the 
lowest measured flow, and 2% of flows are higher than the highest measured flow.  The 
calculated potential error for flows derived from this station’s rating curve is ±13%.

Flows greater than 1,300 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 calculated potential error for high flows derived from this model is 
±20%.  This represents only the potential error in modeling the measured discharges, and 
not the total error of the modeled flows.

Stage Record

Continuous data collection was halted at this site after the station was vandalized in 
December 2004.  Since that time, continuous stage data from the downstream USGS 
station 12208000 M.F. Nooksack River near Deming has been correlated with the 
discrete stage readings from this station.  Time-weighted adjustments were then 
performed on the resulting data set to calibrate the continuous data to the manual stage 
readings.  The correlation and all adjustments are documented in the Hydstra Data 
Workbench.  The calculated potential error for the continuous data is 17%.  This error 
calculation assumes accuracy of the data obtained from USGS.



Future Efforts

Vandalism continues to be a problem at this station.  Ongoing replacement of staff gages 
will be necessary to maintain this data record.  Also, the high gradient of this river makes 
sediment transport a nearly-continuous process.  The rating curve can be subject to 
frequent shifts, and frequent discharge measurements are necessary to maintain accuracy 
in the rating curve.