Willamette River - Vertical Profiles

The City of Portland Bureau of Environmental Services started a new monitoring program in the Willamette River in the summer of 2000 with a sample frequency of two weeks from July to October. Temperature, conductivity, pH, and dissolved oxygen samples were taken every 10 feet at four locations, Table 2.  Vertical profiles were taken from the east and west banks and from the middle of the river for each location. Figure 10 shows temperature profiles for the summer 2000 in the middle of the river at Waverly Country Club. Figure 11 shows dissolved oxygen profiles for the same location and time period. Profiles for the other locations are in Appendices E through H.

Temperature and dissolved oxygen measurements collected by BES in the Willamette River (RM 1.1 to RM 17.9) do not show significant stratification during the summer 2000 below the10-ft depth (Figure 10 and Figure 11). Unfortunately, the sampling program did not measure the near surface temperature and dissolved oxygen above the 10-ft depth except on the first day of the monitoring program (July 12, 2000). In Figure 10 and Figure 11, slight stratification seems to exist in the top 10-ft of the river. Additional vertical profiles for temperature and dissolved oxygen are shown in the websections on temperature and dissolved oxygen. Conductivity and pH show small variations below the10-ft depth. Data for the top 10-ft is also missing for all days except 7/12/2000. Conductivity and pH profiles can be found in the websections with the same name.

Temperature stratification in the Willamette River (RM 1.1 to RM 17.9) could be a consequence of higher water level elevations in the Columbia River than in the Willamette River. This occurs at the end of spring and beginning of the summer. The difference in water levels produces a Columbia River water intrusion in the Willamette River moving upstream creating a bottom wedge of Columbia River water (Bloom, 2000).