01G100 – M.F. Nooksack R. above Clearwater Creek

Technical Notes:  2005 Water Year
Chuck Springer
  
The staff gage station on the Middle Fork Nooksack River above Clearwater Creek was 
monitored throughout water year 2005.  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, these events caused noticeable changes to channel 
geometry, impacting 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 late-August.  
Minimum summer flows for water year 2005 were the same as those for the previous 
water year.

RATING CURVE

The rating curve for the station for water year 2005 covers a range of discharge from 75 
cubic feet per second (cfs) to 4,340 cfs.  The range of stage encountered during the water 
year was 3.9 feet.  The range of discharge encountered during the water year was from 
125 cfs in late-February 2005 to 3,790 cfs in late-November 2004.  The measured 
discharge, ranging from 150 cfs to 1,300 cfs covers only 30% of the magnitude of flows 
encountered during the water year.  However, discharge exceeded the measured range of 
flows only 15% of the time during the water year; discharge was above the measured 
range 3% of the time, and below the measured range 12% of the time during the water 
year.  Flows greater then 1,300 cfs were modeled using the established relationship 
between stage and velocity during the highest measured flows, along with a surveyed 
high flow cross-section.  The accuracy of flows derived from this model is estimated to 
be within ±20%.

STAGE RECORD

Staff gage readings taken at this site were correlated with stage height data from USGS 
station 12208000 – M.F. Nooksack R. nr Deming (coefficient of determination (r2)= 
0.91), which is located 4.6 miles downstream.  These stage values were adjusted based on 
the results of the correlation, and further adjusted to weekly observations taken at the 
Ecology site.  The resulting continuous data record was then applied to the established 
rating curve for the site to produce an estimated continuous record of discharge.

FUTURE EFFORTS

More discharge measurements are needed at this station to augment both the high and 
low ends of the rating curve.  Cross-sectional and longitudinal surveys will take place 
during the summer of 2006.

cws