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Upper Chehali« River Svitem Water Quality 



Ab seen in Chapter 5, the water quality problem in the rnxd-Chehalis is 

 reasonably well documented. However, there are a number of areas where 

 information could be improved. 



Continuous water quality monitoring .- There are some problems with existing 

 water quality monitoring. For example, oxygen is measured each month at one 

 time of day, although periodB of daily oxygen lows lasting less than a month 

 are strongly suspected. Continuous oxygen monitoring should be invoked, 

 especially at known problem locations. Nutrient levels should be monitored 

 often enough to detect changes in loading over the season. Enough stations 

 need to be chosen to isolate the effects of all major point sources, and 

 define the relative importance of tributaries as nonpoint sources. Monitoring 

 should occur annually from July through mid-October. 



Extent of water quality problems .- Existing plans for analysis have apparently 

 not yet been focused sharply on all degraded qualities of the water. In 

 particular, no plans have been made to use existing temperature models to 

 determine how increased shading may reduce the temperatures. The models should 

 be used to predict the cooling effect of bank revegetation, with the goal of 

 directing tree planting efforts where they can do the most good. 



Acute toxic contamination .- Additional information is needed to further reduce 

 the risk of acute toxic contamination, for example from improper or illegal 

 waste disposal from agriculture or light industry. 



Relation between water quality and quantity .- Detailed investigations are need 

 to increase understanding of the relation between water quality and water 

 quantity. For example, municipal and agricultural water withdrawal may 

 influence temperature and nutrient concentration. 



Septic contamination of river .- A hydrological study is desirable to determine 

 whether the aquifer in the vicinity of Centralia has a net flow into or out of 

 the Chehalis river during the summer. This would help the CRC and the Lewis 

 County Conservation District decide how much emphasis to place on the 

 connection between septic systems and river nutrient loading. It would also 

 help the City plan for future water supply. 



Water Quantity 



Wynoochee Dam 



There may be opportunity for further enhancement of Wynoochee River summer 

 flows, since the City of Aberdeen now uses far less than its water right. The 

 history of determining actual Wynoochee "fish flows" should be reviewed, and 

 arguments for and against a full-scale instream flow study should be made 

 explicit. If an instream flow study were chosen as the basis for negotiating 

 flows, the necessary field work could be completed in one to two years. 



