01R090 - California Cr. @ Valley View Rd.
Technical Notes:  2005 Water Year
Chuck Springer

The instantaneous streamgaging station on California Creek at Valley View Road was monitored 
throughout water year 2005.  During the water year, two discharge measurements were made and 
41 discrete stage readings were taken at this station.

Rating Curve

The purchase of an Acoustic Doppler Current Profiler (ADCP) by the Department of Ecology in 
2005 made measuring discharge at this station possible for the first time.  Rating Table 1 was 
developed for this station beginning in April 2005.  Flows encountered during water year 2005 
range from less than 2 cubic feet per second (cfs) to 33.5 cfs.  Two of the three discharge 
measurements used to develop this rating were taken during water year 2005.  The measured 
flows for this rating, ranging from 2.5 to 118 cfs and cover nearly the entire range of flows 
encountered while Rating Table 1 was in effect during water year 2005.  Six of the discrete stage 
readings exceeded the lowest measured flow.  Johnson’s method was used (e = 1.4) to 
temporarily straighten the stage-discharge relationship.  Interpolations between discharge 
measurements and extrapolations to half of the lowest measured flow and twice the highest 
measured flow were then performed.  The calculated potential error for flows derived from 
Rating Table 1 is ±12%.

In late July 2005, aquatic weed growth began to impede flow, impacting the stage-discharge 
relationship.  This process continued through the rest of the summer and into the fall.  A 
discharge measurement made on October 5 captured this shift in progress, and an intermediate 
rating table (Table 2) was developed to reflect the gradual shift up to that point.  Water year 
2005 ended in transition to this rating table, which will be discussed in the water year 2006 
technical notes.

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, or “tape down” readings taken from a reference point on the Valley View Road Bridge 
yielded two outliers during water year 2005.  In both cases, it was determined that readings 
taken in the field were transposed.  Because this could not be determined conclusively, all 
readings (staff gage and tape down) taken on both dates were flagged as estimates.

Future Efforts

This station shifts seasonally due to rampant grass and algae growth.  Ongoing frequent 
discharge measurements and when possible, point of zero flow measurements will be necessary to 
monitor these shifts.