|Document Type:||Journal Article|
|Title:||Timing and extent of a flow reversal in the lower Columbia River|
|Author:||Shirley M. Clark, George R. Snyder|
|Journal:||Limnology and Oceanography|
Two thermal electric plants are scheduled for installation on the lower Columbia River. They would use Columbia River water as coolant and discharge it back to the river.
Reversal of Columbia River hydraulic flow occurs up to 40 km from the river mouth throughout the year. During low discharge, the reversal point moves farther upstream than during high discharge. During the filling of John Day Reservoir in April 1968, a period of low discharge existed in the Columbia River below John Day Dam. This reduced flow period produced river discharge rates similar to those estimated for the future. Thus an excellent opportunity to study flow reversal at the site of the proposed waste heat discharge, under anticipated future flow conditions, was made available. On 17 April 1968, such a study was undertaken near Prescott, Oregon.
This study showed that an extensive upstream movement of water can occur near Prescott during low flow stages of the Columbia River. Under these conditions, thermal electric plants would use the· same water more than once for cooling their condensers and repeatedly subject fixed masses of water to their heated effluents. Reversal of the river flow would cause a periodic concentration of rejected heat from the thermal electric plant in sections of the river downstream, producing an increase in the temperature of isolated volumes of water that is above the average rise for the river. The study points out a possible difficulty inherent in placing a thermal pollutant source on a reversing river flow. This problem should be studied intensively to evaluate the biological risk before final designs of the proposed installations are accepted.