The best (but by no means a completely satisfactory) quantitative 

 measure of the organic pollution burden carried by a stream at the time 

 of sampling is the Biochemical Oxygen Demand (bOd) « The BOD deter- 

 mination represents the Quantity of oxygen consumed in a sealed water- 

 sample during a five-day incubation period at 20'^ C. The five-day 

 BOD grossly approximates tv/o^thirds of the total quantity of oxygen 

 that will be reauired fo." complete satisfaction of tl-ie oxygen-consuming 

 wasteso The reverse of the DO concentrations ordinarily is used to 

 assess BOD determinations, namely; a five-day BOD betv/een zero and 

 three parts per million is considered to indicate light pollution, a 

 five-day BOD between Three and five parts per million as indicating 

 moderate to moderately heavy organic pollution, and determinations 

 exceeding five parts per million as indicative of serera pollutiono 



Conductivitys per se^, does not measure offensive pollution in 

 that an increase in the electrical conductivity merely indicates an 

 increase in the ionic concentration which may, or may not, be composed 

 of ions toxic to fish lifeo It is used, primarily as an index of 

 inorganic pollutiono 



Considering the results obtained from stream sampling during the 

 September-October^ 1948^, reconnaissance survey, the following tentative 

 conclusions appear warranted; 



lo Main -Stem Willamette River o 



The main-stem Willam&tte, betv/een the Springfield Bridge above 

 Eugene and the Steel Brid,r:e in Portland, was surveyed on October 14, 

 15 and 16o Several par-cial surveys were made both before and after 

 the main survey. 



The results of the complete mid-October survey indicated that, 

 in spite of an increasing BCD and Gonductivit;y and some decrease in 

 DO at progressive dovmstream stations, no oxygen block existed at, 

 the timeo Superficially j, at least, the river was open to the 

 passage of migratory fishes. The 1948 results differed in this major 

 respect from those obtained by Merr^.'field and Wilinot during a comparable 

 period in 1944o The 1943 DO and ROD data, s\iperimposed upon the DO 

 data from Merryfield and Wilnot (1945), are shovm in Figure 1. 



The difference in the DO picture obtained during October, 1944, 

 and during October 1948, unquestionably stemmed from the much greater 

 volixrae of river discharge prevailing during 1948o As shown in Figure 2, 

 the river discharge during the 1948 survey v/as much greater than that 

 prevailing at the time of the 1944 survey by Merr}''field and Wilmoto 



14 



