Phosphorus and E. coli Measurements in Oregon Creek Subbasins During 1996 Low Flow

Phosphorus and Escherichia coli concentrations were measured at 59 total sites across the Fanno and Bronson Creek subbasins in September 1996. The dataset was collected as part of a cooperative study between the Unified Sewerage Agency of Washington County, Oregon, and the U.S. Geological Survey. It characterizes summer base-flow water quality conditions in these tributaries of the Tualatin River Basin.

Use Cases

• Analyze spatial patterns of total phosphorus concentration (0.1-0.2 mg/L range) across 19 main-stem and 22 tributary sites in Fanno Creek.
• Identify sites exceeding the E. coli recreational contact criterion (406 organisms/100 mL), which occurred at 70% of Fanno Creek sites.
• Compare contamination levels between the Fanno Creek and Bronson Creek subbasins, where E. coli exceedances differed (70% vs. one-third of sites).
• Investigate potential pollution sources by correlating elevated phosphorus levels at specific sites like Pendleton Creek with described local factors.
• Model ground-water discharge influence on base-flow phosphorus levels using concentration data near the estimated background level of 0.14 mg/L.

Strengths

• Data collected from 59 distinct sampling sites across two subbasins provides spatial coverage.
• Measurements target a specific hydrological condition (summer base-flow), allowing for controlled seasonal analysis.
• Report includes specific concentration ranges and exceedance rates against a regulatory criterion (406 E. coli/100 mL).

Limitations

• Dataset is from a single sampling period in September 1996, lacking temporal variability or long-term trends.
• Sample size is limited to one low-flow event, not capturing conditions during storms or other seasons.
• Specific column names, data formats, and row counts are not provided in the description.

Provenance

Source

U.S. Geological Survey in cooperation with the Unified Sewerage Agency of Washington County, Oregon.

Collection Method

Field sampling of water quality and stream discharge during base-flow conditions.

Time Range

September 1996 (specifically September 10, 1996, for Fanno Creek).

Freshness

1996-09-24

Geography

Fanno Creek and Bronson Creek subbasins within the Tualatin River Basin, northwestern Oregon, USA.