INTERCHANGE OF STREAM AND INTRAGRAVEL 

 WATER IN A SALMON SPAWNING RIFFLE 



by Walter G. Vaux 



Fisheries Aid 



Fisheries Research Institute 



University of Washington 



Seattle, Washington 



ABSTRACT 



Dissolved oxygen is supplied to intragravel water in a salmon spawning riffle 

 through (1) interchange of water from the stream into streambed gravel, and (2) 

 ground-water flow. The primary variables that control interchange are gradients 

 in the stream profile, permeability of the gravel bed, and dimensions of the bed. 



The delivery of dissolved oxygen to intragravel water and the way in which rate 

 of delivery is affected by stream profile, permeability, and dimensions of the bed 

 are explained. 



INTRODUCTION 



While buried in the gravels of streams for 

 6 to 9 months, eggs and larvae of the Pacific 

 salmon (Oncorhynchus) are subjected to various 

 environmental factors causing mortality, such 

 as floods and freezing (Royce, 1959). Other 

 important factors that affect mortality are 

 dissolved oxygen content and rate of flow of 

 intragravel water* that bathes buried salmon 

 eggs and larvae (Wickett, 1958). 



Oxygen dissolved in intragravel water is 

 consumed by biological and chemical proc- 

 esses and must be resupplied by diffusion, 

 ground-water flow, or circulation between 

 aerated stream water and water in the gravel. 

 The circulation between stream and intra- 

 gravel water is called interchange and is 

 either an upward or downward flow. 



The Fisheries Research Institute started 

 studies of interchange in 1948 under the direc- 

 tion of Dr. William F. Thompson. These 

 studies were interrupted in 1949 and were not 



resumed until 1957 when they became part of 

 a project to study effects of logging on produc- 

 tivity of pink salmon (Oncorhynchus gorbuscha) 

 in streams of Southeastern Alaska.* In 1957 

 the occurrence of interchange was qualita- 

 tively demonstrated in a spawning riffle by 

 injecting dye into the gravel through stand- 

 pipes and detecting the appearance of dye at 

 the surface of the gravel downstream from 

 the point of injection. In 1958 and 1959 pre- 

 liminary studies were conducted by the writer 

 in a small flume at the University of Wash- 

 ington Chemical Engineering Laboratory to 

 identify some of the variables that control 

 interchange. During the summer of 1959 

 studies conducted in a pink salmon spawning 

 riffle in Indian Creek in the Kasaan Bay 

 area of Southeastern Alaska (fig. 1) provided 

 qualitative verification of the dependence of 

 interchange on stream gradient and pro- 

 file. 



The study of interchange is being continued. 

 In addition to field investigations, a quantitative 



'The term "intragravel water" refers to water oc- 

 cupying interstices in gravel beds. 



* Contract with Bureau of Commercial Fisheries, 

 U,S. Fish and Wildlife Service. 



