8. Ratio of length to width. 



9. Ratio of width to depth as water 

 surface falls during depletion 

 period. 



Impoimdments studied were the Yale 

 and Merwin Reservoirs on the Lewis River, 

 Grand Covilee Equeilizing on the Columbia 

 River Basin Main Canal, and the Roosevelt, 

 McNary and Bonneville Reservoirs on the 

 Columbia River. Relatively email and shal- 

 low impoundments, like the Bonneville and 

 Rock Island Reservoirs, were observed to 

 have no appreciable effect on downstream 

 water temperature. 



Table I3 shows the average monthly 

 temperature changes through the reservoirs 

 for the months when data had been obtained. 



The data from which these temperature 

 differences were obtained were limited, 

 excepting for Lake Roosevelt where daily 

 temperatures were available from Fish and 

 Wildlife Service thermograph records. Other 

 temperature differences were observed from 

 one to four times monthly. A discussion of 

 this table follows: 



Yale: Impoundment comnenced in this 

 reservoir on August 1, 1952. It is a medium 

 depth, average sized reservoir, having a 

 length to width ratio of I3.6. The Lewis 

 River, flowing into the reservoir, heads up 

 in the glaciers on Mt. Adams and Mt. St. 

 Helens and flows through timbered country to 

 the reservoir. For this reason, the river 

 is relatively cold the year around and the 

 reservoir discharges a water wanaer than the 

 inflow for most of the year. The large 



Table 13- — Average monthly temperature change in water frcn 

 upstream to downstream of resemrolrs* 



* Plus sign Indicates temp, rise In degrees F through reservoir; minus, temp, fall; - Indicates no data. 



1 Data for 1954-55 traa University of Washington data. 



^ Data for 1944-45 emd 47 from Fish and Wildlife Service thermograph ivcords. 



3 Temp, above McNary Dam measured at Pasco. This shows temp, change euscountlng for wamer or colder 

 Snake River Inflow below Pasco. 



•-J. 



