II. 1948 STUDIES 



Ao Reconnaissance Survey ^ September -October , 1948 o 



Pollution research was added to the work program of Western 

 Fish=Cultural Investigations on July Ij 1948<, A cooperative project 

 vrith the Section of Sanitary Engineering at Oregon State College was 

 effected immediately thereafter© By the time that funds available 

 for pollution studies were known, personnel concentrated,, and 

 laboratory facilities readiedj, the 1948 low-water stage of the 

 Willamette had passedo Likewise, the summer of 1948 was accompanied 

 by relatively high river flows and cool temperatures and it did not 

 constitute a critical year for evaluating pollution at its maximtim 

 effect. 



It was decided that a reconnaissance survey of the Willamette 

 and its m&ior tributaries comprised the best use of the limited time 

 available for field studies before the onset of the fall reins o It 

 was fully recognized that a survey of this t7'pe would be subject 

 to all the limitations inherent to spot sampling and that the r--3'.]lhs 

 would be indicative but not conclusive » The survey should reveal all 

 potential sources of pollution qualitativelj/- if not quantitatively 

 and thus indicate areps for future and more critical study. 



Standard procedures were employed for the dissolved oxygen 

 and biochemical oxygen demand tests. The field studies were under-- 

 taken on September 9„ 1948, and each major tributary sampled at 

 progressive intervals downs tream--starting at a point above all 

 apparent sources of major pollutiono 



The results obtained during the six-week period before river 

 stages rose significantly with increasing rainfall are listed on 

 Table lo 



Bo I nterpretation of Results 



Five parts per million of dissolved oxygen customarily are 

 accepted as the threshold betv;een a satisfactory and an unsatis- 

 factory environment for cold-water fisheso Dissolved oxygen 

 concentrations ranging >-etween three and five parts per million 

 are considered to indicate moderate pollution by oxygsn^Gonsuming 

 wastes, and concentrations below three parts per million indioatr/e 

 of severs pollutiono A reduced dissolved oxygen concentration '.DO;, 

 often expressed in terms of percentage saturation to compensate for 

 variations in temperature, indicates only the degrading effecta of 

 oxygen-consuming wastes that have occurred up to the time and place- 

 of saiipling, and it offers no index of any further degradation that 

 may be expected from the oxygen-consuming wastes. 



