88 U. S. BUREAU OF FISHERIES 
Studies of impounded waters were continued at Elephant Butte 
Reservoir, in cooperation with the United States Reclamation Service 
and the National Research Council, and at Lake Mead in cooperation 
with the same agencies and the National Park Service. 
HYDRAULIC SECTION 
HARLAN B. HoLmes, in charge 
For a number of years the Bureau of Fisheries has felt the need for 
a well-organized section in the Division of Scientific Inquiry in 
which the combination of biological and engineering talent could 
be applied to fish and fishery problems created by the construction 
of dams, reservoirs, and diversions for the purposes of power, iri- 
gation, navigation, and flood control. ‘The perpetuation of fish popu- 
lations following the development of such projects requires a detailed 
analysis of the changes in biological and physical conditions, and of 
the biological requirements of the fish that inhabit the areas involved. 
As a general rule, Re solution of those problems involves the con- 
struction of fishways to enable upstream migrants to pass over dams 
and other ee ne and the installation of screens to prevent the 
entrance of downstream migrants into irrigation diversions and 
hydraulic turbines, in which they would be lost or injured, 
For the study of these problems of fish protection, and the con- 
struction and operation of fishways, screens, and other protective 
works, there has been created within the Division of Scientific In- 
quiry a Hydraulic Section. Mr. Harlan B. Holmes has been ap- 
pointed to the position of Aquatic Biologist, in charge, and Mr. Olaf 
W. Lindgren has been employed in the capacity of Associate Hy- 
draulic Engineer. Funds for this section first became available in 
July 1938, but activities were not beeun until late in the year when 
Mr. Lindgren entered the service. Mr. Holmes, who for a number 
of years has been loaned to the War Department, Corps of Engineers, 
in connection with fish problems at the Bonneville Dam, was not 
available to the Bureau of Fisheries until October 1939. Other mem- 
bers of the biological staff of the Seattle Laboratory have taken 
part in the work of fish protection. 
The work of the Hydraulic Section during the year has included 
the partial construction of 4 large fish screens in Federal irrigation 
canals, the reconstruction of 2 existing screens, the operation of 6 
screens throughout the irrigating season, aid in the study of fish 
problems in connection with the Shasta. Dam Project, being con- 
structed on the Sacramento River in California, and a preliminary 
study of fish problems in connection with many other Federal water 
projects. Consulting assistance in connection with fishway and 
screen problems also has been furnished to the conservation agencies 
of several States. 
All of the screens operated by the Bureau of Fisheries were on 
Federal canals in the Yakima Valley; the Kittitas, Tieton, and Sun- 
nyside canals on Bureau of Reclamation projects; and the Ahtanum, 
Old Indian, and Wapato canals operated by the Indian Service. 
One of the screens reconstructed during the year is in the Pishkun 
Reservoir of the Sun River Project in Montana. It is a bar-type 
