01D100 – Sumas River @ Telegraph Road
Technical Notes:  2006 Water Year
Chuck Springer

The instantaneous streamgaging station on the Sumas River at Telegraph Road was 
monitored throughout water year 2006.  During the water year, seven discharge 
measurements were made and 34 instantaneous stage readings were taken at this station, 
at stages ranging from 1.90 feet to 10.34 feet.

Rating Curve

This station was monitored throughout water year 2006 on rating table 5, which was 
established in January 2005.  The rating table covers a range of discharge from 7.8 cfs to 
1,430 cfs.  Seven of the 13 measurements used to develop this rating were taken during 
water year 2006.  The measured flows for this rating, ranging from 10.6 cfs to 219 cfs, 
cover only 15% of the rating curve.   However, during water year 2005, only three of the 
instantaneous stage readings fell outside the measured range of flows.  Two readings 
were lower than the lowest measured flow, and one reading was higher than the highest 
measured flow.  The resolution of rating table 5 at flows below 32 cfs is extremely poor.  
Rating curve segments below 32 cfs are qualified as estimates.  The calculated potential 
error for flows derived from the rating curves used during water year 2006 for this station 
is ±21%.

Flows greater than 219 cfs had been modeled as part of the water year 2005 review.  
Refer to the 2005 technical notes for details.  

Stage Record

The stage record for this station is comprised of discrete (instantaneous) staff gage 
readings taken during weekly visits.  A linear regression of staff gage readings versus 
depth to water surface readings taken from a reference point on the Telegraph Road 
Bridge yielded no outliers during water year 2006.  Confidence is high that there were no 
erroneous readings during the water year.

Future Efforts

Due to fine-grained substrate, coupled with rampant algae and grass growth during the 
summer months, the discharge rating for this station shifts frequently (the rating shifted a 
few days after water year 2006 ended).  Ongoing discharge measurements at frequent 
and regular intervals will be necessary at this site.