USGS Scientific Investigations Report 2010–5008 Use of Continuous Monitors and Autosamplers to Predict Unmeasured Water-Quality Constituents in Tributaries of the Tualatin River, Oregon

Table 16. Preliminary functional model forms for total suspended solids, total phosphorus, and Escherichia coli bacteria at non-target tributary sites in the Tualatin River basin, Oregon, 2002–04.

[Model forms are based on autosampler-only data. If the adjusted-R² of the optimum model, based on minimization of Mallow’s Cp, was greater than 0.5, then the functional form of the optimal model is shown, without model coefficients. If the adjusted-R² was less than 0.5, then no model is shown and the result is listed as N/A (not applicable). Turb, Q, and SC are the explanatory variables of turbidity (in Formazin Nephelometric Units), discharge (in cubic feet per second), and specific conductance (in microsiemens per centimeter), respectively. Abbreviations: TSS, total suspended solids; TP, total phosphorus; E. coli, Escherichia coli bacteria; log, base 10 logarithm; f, a function of indicated constituents]

Site	Functional model form
Site	TSS	TP	E. coli
Beaverton Creek at SW 170th Ave.	logTSS=f(Turb,SC,Q)	logTP=f(Turb,SC,Q)	N/A
Chicken Creek at Scholls-Sherwood Highway	logTSS=f(Turb,SC,Q)	logTP=f(Turb,SC,Q)	N/A
Rock Creek at Woll Pond Way near Hillsboro	logTSS=f(Turb,SC,Q)	logTP=f(SC,Q)	N/A
Gales Creek at Old Highway 47	logTSS=f(Turb,SC,Q)	logTP=f(Turb,SC,Q)	logE. coli=f(Turb,SC,Q)