HOLLISTER, G. 



1936. Caudal skeleton of Bermuda shallow water 

 fishes. I. Order Isospondyli : Elopidae, Megalopi- 

 dae, Albulidae, Clupeidae, Dussumieriidae, En- 

 graulidae. Zoologica (N.Y.) 21:257-290. 



1937a. Caudal skeleton of Bermuda shallow water 

 fishes. II. Order Percomorphi, Suborder Perces- 

 oces: Atherinidae, Mugilidae, Sphyraenidae. 

 Zoologica (N.Y.) 22:265-279. 



1937b. Caudal skeleton of Bermuda shallow water 

 fishes. III. Order Iniomi: Synodontidae. Zool- 

 ogica (N.Y.) 22:385-399. 



1940. Caudal skeleton of Bermuda shallow water 

 fishes. IV. Order Cyprinodontes : Cyprinodonti- 

 dae, Poecilidae. Zoologica (N.Y.) 25:97-112. 



1941. Caudal skeleton of Bermuda shallow water 

 fishes. V. Order Percomorphi : Carangidae. Zool- 

 ogica (N.Y.) 26:31-45. 



HuBBS, C. L., AND K. F. Lagler. 



1958. Fi.shes of the Great Lakes region. Revised 

 ed. Cranbrook Inst. Sci., Bull. 26, 213 p. 

 Lagler, K. F., J. E. Bardach, and R. R. Miller. 



1962. Ichthyology. J. Wiley, N.Y. 545 p. 



Grant L. Miller 



3058 Crescent Drive 



Salt Lake City, UT 8U106 



Sherrell C. Jorgenson 



Bureau of Sport Fisheries and Wildlife 

 Great Lakes Fishery Laboratory 

 P.O. Box 6U0, Ann Arbor, MI ^8107 



FREQUENCY AND DURATION OF FLOW 



REVERSAL IN THE LOWER COLUMBIA 



RIVER, APRIL 1968-MARCH 1970 



The hydraulic head generated by some heights 

 of tide can result in changes in direction of cur- 

 rent in the lower Columbia River when volume 

 discharges fall below a critical value. In connec- 

 tion with this phenomenon, Clark and Snyder 

 (1969) conducted a study to determine the tim- 

 ing and extent of reversal of flow during an 

 extreme condition of low discharge of water 

 from the river. They determined that flow re- 

 versals could increase the accumulation of dis- 

 charged effluents per given volume of river 



water by as much as 3.5 times over the accumu- 

 lation at mean flow rates. Their report showed 

 the need for a continuing record of direction of 

 current in the lower Columbia River to deter- 

 mine the importance of flow reversal at different 

 discharge rates. To help satisfy this need, a 

 floating laboratory (Snyder, Blahm, and McCon- 

 nell, 1971) was established on the lower Colum- 

 bia River at river kilometer 117.5 (river mile 73) 

 near Prescott, Oreg., where speed and direction 

 of current were recorded. This report describes 

 the flow-reversal phenomenon at river kilometer 

 117.5 from data collected between April 1968 

 and March 1970. 



Procedure 



The velocity of the river current was measured 

 with a Savonius meter' suspended from the lab- 

 oratory to determine the frequency and duration 

 of flow reversal in the lower Columbia River. 

 With the exception of 21 days, the flow was mon- 

 itored continuously for a 2-year period. Flow 

 data obtained at Prescott were related to the 

 daily discharge of the river and to the time and 

 height of ocean tides near the river's mouth at 

 Astoria, Oreg. 



Daily average flow for the period 1 April 1968 

 to 30 June 1969, was "gauged flow" furnished 

 by the U.S. Geological Survey office in Portland, 

 Oreg.; daily average flow for the period 1 July 

 1969 to 31 March 1970, was from information 

 furnished by U.S. Geological Survey offices in 

 Portland, Oreg., and Tacoma, Wash. Time and 

 height of oceanic tides were for Astoria, Oreg.; 

 these data were obtained from tide charts of 

 the NO A A (National Oceanic and Atmospheric 

 Administration) National Ocean Survey. 



Our observations of direction and speed of 

 current were used to determine the duration and 

 frequency of flow reversals. Only those flow 

 reversals of 60-min duration or longer were con- 

 sidered to constitute true reversals. Duration 

 of flow reversal was defined as the time interval 

 between positive downstream flows wherein the 



* Reference to trade names does not imply endorse- 

 ment by the National Marine Fisheries Service, NOAA. 



312 



