01R090 - California Cr. @ Valley View Rd.
Technical Notes:  2007 Water Year
Chuck Springer

The instantaneous streamgaging station on California Creek at Valley View Road was monitored 
throughout water year 2007.   During the water year, four discharge measurements were made 
and 30 discrete stage readings were taken at this station.

Rating Curve

This station started water year 2006 on Rating Table 4.  Flows encountered while Table 4 was in 
effect during water year 2007 range from 4.7 to 6.4 cubic feet per second (cfs).  One of the six 
discharge measurements used to develop this rating were taken during water year 2007.  The 
measured flows for this rating, ranging from 4.3 to 118 cfs, cover the full range-of-flows 
encountered while Rating Table 4 was in effect during water year 2007.  Johnson’s method was 
used (e = 2.4) to temporarily straighten the stage-discharge relationship.  Interpolations between 
discharge measurements and extrapolations to half the lowest measured flow and twice the 
highest measured flow were then performed.  The calculated potential error for flows derived 
from this rating table is ±13%.

A storm event in November 2006 caused substantial channel fill, shifting the stage-discharge 
relationship back to Rating Table 3.  Flows encountered while Rating Table 3 was in effect 
during water year 2007 range from 2.6 to 127 cfs.  The measured flows for this rating, ranging 
from 15 to 118 cfs cover 83% of the range of flows encountered.  Five of the 18 discrete stage 
readings exceeded the lowest measured flow, and one exceeded the highest measured flow.  
Johnson’s method was used (e = 4.4) to temporarily straighten the stage-discharge relationship.  
Interpolations between discharge measurements and extrapolations to half the lowest measured 
flow and twice the highest measured flow were then performed.  The calculated potential error 
for flows derived from this rating table is ±13%.

Another storm event in April 2007 scoured the channel at this site.  This shift is represented by 
Rating Table 5.  The exact timing of this shift was not known, however one discharge 
measurement was taken while the shift was in progress.  The shift was thus phased such that the 
discharge predicted by the transitional rating on the date of this measurement matched the 
measured discharge.  Flows encountered while Rating Table 5 was in effect during water year 
2007 range from 2.3 to 31.7 cfs.  The measured flows for this rating, ranging from 4.7 to 118 cfs, 
cover all but the lowest 8% of the range of flows encountered.  Seven of the 16 discrete stage 
observations exceeded the lowest measured flow.  Johnson’s method was used  
(e = 2.0) to temporarily straighten the stage-discharge relationship.  Interpolations between 
discharge measurements and extrapolations to half the lowest measured flow and twice the 
highest measured flow were then performed.  The calculated potential error for flows derived 
from this rating table is ±21%.

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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 
did not yield any obvious outliers during water year 2007, indicating that there likely were not 
any severely erroneous readings.  However, the standard deviation of this regression was 0.05 ft. 
so it is possible that minor errors in the readings would go undetected.

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.