01R090 - California Cr. @ Valley View Rd.
Technical Notes:  2006 Water Year
Chuck Springer

The instantaneous streamgaging station on California Creek at Valley View Road was monitored 
throughout water year 2006.  During the water year, six discharge measurements were made and 
34 discrete stage readings were taken at this station.

Rating Curve

This station started water year 2006 in transition from Rating Table 1 to Rating Table 2.  This 
shift was caused by aquatic weed growth at the site during summer 2005.  (See the water year 
2005 technical notes for this station for a discussion of Rating Table 1.)  One discharge 
measurement taken on October 5, 2005 was taken amid this transition.  The shift from Rating 
Table 1 to Rating Table 2 was prorated such that the discharge predicted by the transitional 
rating on October 5, 2005 matches the discharge measured on that date.  

Flows encountered while Rating Table 2 was in effect during water year 2006 range from  
1.8 cubic feet per second (cfs) to 118 cfs.  Two of the four discharge measurements used to 
develop this rating were taken during water year 2006.  The measured flows for this rating, 
ranging from 15 to 118 cfs, cover nearly 90% of the range-of-flows encountered while Rating 
Table 2 was in effect during water year 2006.  However, eight of the 12 discrete stage readings 
exceeded the lowest 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.

A storm event in January 2006 caused a channel scour.  This shift is represented by Rating  
Table 3.    Flows encountered while Rating Table 3 was in effect during water year 2006 range 
from less than 2.2 to 64.6 cfs.  The measured flows for this rating, ranging from 4.3 to 118 cfs 
cover nearly all of the range of flows encountered; however, 16 of the 28 discrete stage readings 
exceeded the lowest measured flow.  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 the rating curve used during water year 
2006 for this station is ±13% for Rating Table 2, and ±14% for Rating Table 3.

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 one outlier during water year 2006.  It was determined that this outlier was due to a 
misread tape down.  Because this could not be determined conclusively, all readings (staff gage 
and tape down) taken on the date in question 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.