Science and Education Administration, U.S. Department of 

 Agriculture, and the U.S. Fish and Wildlife Service. Information on 

 the distribution of these aquatic pests and the problems they cause to 

 irrigation or multiple use water systems has been obtained over the 

 years through the cooperation of personnel of the Water and Power 

 Resources Service and private irrigation districts. Many aquatic 

 organisms were obtained from authoritative references listed in the 

 bibliography. The authors wish to thank the many individuals whose 

 contributions have made publication of this identification guide 

 possible. 



The original text was prepared by N. E. Otto, presently Supervisory 

 Biological Scientist, and T. R. Bartley, chemist, both of the Division 

 of Research, Engineering and Research Center; the final review and 

 preparation of the original edition were performed by E. H. Larson, 

 Division of Engineering Support, Bureau of Reclamation, Engineering 

 and Research Center, Denver, Colorado. Also, the original illustrations 

 were prepared by D. W. Cunningham of the Bureau of Reclamation, 

 Lower Missouri Regional office in Denver. 



TTie additions and revisions for this second edition were authored 

 by J. S. Thullen, Botanist, Division of Research, and edited by M. J. 

 Cochran of the Technical Publications Branch, both of the 

 Engineering and Research Center. The additional illustrations used 

 in the second edition were prepared by J. M. Evans, Supervisor, 

 Graphic Arts Unit, also of the Engineering and Research Center. 



