01Q070 - Dakota Cr. @ Giles Rd.
Technical Notes:  2006 Water Year
Chuck Springer

The instantaneous streamgaging station on Dakota Creek at Giles Road was monitored 
throughout water year 2006.  During the water year, four discharge measurements were made 
and 35 discrete stage readings were taken at this station.

Rating Curve

This station started water year 2006 on Rating Table 3.  Flows encountered while Rating Table 3 
was in effect during water year 2006 range from 0.6 cubic feet per second (cfs) to 167 cfs.  Four 
of the 12 discharge measurements used to develop this rating were taken during water year 2006.  
The measured flows for this rating, ranging from 1.3 to 173 cfs, cover nearly the entire range of 
flows encountered while Rating Table 3 was in effect during water year 2006.  Only three of the 
discrete stage readings exceeded the lowest measured flow.  Johnson’s method was used  
(e = 2.9) 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 station finished the water year in transition for Rating Table 3 to Rating Table 4.  Rating 
Table 4 will be discussed in the water year 2007 technical notes.

The calculated potential error for flows derived from the rating curve used during water year 
2006 for this station is ±18%.

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 Giles Road Bridge yielded 
one outlier during water year 2006.  It was determined that the tape down reading was most 
likely erroneous; however, because this could not be determined conclusively, the staff gage 
reading on the date in question was flagged as an estimate.

Future Efforts

This station tends to see beaver activity every summer, followed by washouts of those dams 
during winter storm events.  Ongoing frequent discharge measurements and, when possible, point 
of zero flow measurements will be necessary to monitor these shifts.