PREFACE 



Extensive infestations of obnoxious plants and certain aquatic 

 animals cause problems on irrigation systems, such as reduction in 

 carrying capacity of the system, increased evaporation and seepage, 

 clogging of structures, adverse environmental impacts, and water loss 

 through transpiration. Because of the many problems created by these 

 growths, steps are usually necessary to control them or prevent their 

 occurrence. 



The methods employed to control these plants and animals differ 

 widely due to differences in the organisms, such as growth habitat, 

 organism metabolism, size, growth stage, and genetic characteristics. 

 Correct identification of the organism is therefore important to the 

 proper control recommendation. 



The simplified identification guide was prepared in response to 

 requests from irrigation project operators and other personnel involved 

 with biological problems requiring identification aids. It consists 

 essentially of an illustration and a narrative description of some of the 

 commonly observed organisms that become pests on the operation of 

 irrigation systems in the Western United States. Not all animal pests 

 that inhabit irrigation systems are included because many of these 

 common ones such as muskrat, certain fish, and crayfish are readily 

 recognizable by irrigation operating personnel. Some of the more 

 serious and marginal ditchbank weeds have been included to illustrate 

 a few typical problems on canals and drains. 



The narrative descriptions have been written primarily for use by 

 Water and Power Resources Service field personnel and water user 

 organizations directly concerned with the problems. They are not 

 intended to be taxonomic descriptions of the species discussed. The 

 illustrations include drawings of the entire organisms, with inserts to 

 depict key identifying features, both vegetative and floral. Living 

 material was used in most cases for reference in preparing the drawings. 

 Individual species will vary in size, coloration, and other detailed 

 features from those depicted. The overall characteristics illustrated are 

 intended to show the field personnel sufficient features to permit a 

 tentative identification. Should confirmation of this identification be 

 needed, it is suggested that specimens be sent to a local experiment 

 station or to the Chief, Division of Research, Code D-1522, 

 Engineering and Research Center, Denver, Colorado, for examination. 



The information used in this booklet was obtained from various 

 sources. A considerable portion of it has been derived from aquatic 

 weed research studies conducted by the Water and Power Resources 

 Service (formerly Bureau of Reclamation) in cooperation with the 



