of a heated effluent into the hypolimnion will be 

 desirable, such practice is not recommended and 

 water for cooling should not be pumped from the 

 hypolimnion to be discharged to the same body of 

 water. 



(2) The normal daily and seasonal tempera- 

 ture variations that were present before the addi- 

 tion of heat due to other than natural causes 

 should be maintained. 



(3) The recommended maximum temperatures 

 that are not to be exceeded for various species of 

 warm- water fish are given in table III-l. 



Cold Water Biota: Because of the large number 

 of trout and salmon waters which have been de- 

 stroyed, made marginal, or nonproductive, remain- 

 ing trout and salmon waters must be protected if 

 this resource is to be preserved. 



Inland trout streams, headwaters of salmon 

 streams, trout and salmon lakes, and the hypolim- 

 nion of lakes and reservoirs containing salmonids 

 and other cold water forms should not be warmed 

 or used for cooling water. No heated effluents 

 should be discharged in the vicinity of spawning 

 areas. 



For other types and reaches of cold-water 

 streams, reservoirs and lakes, the following re- 

 strictions are recommended: 



( 1 ) During any month of the year heat should 

 not be added to a stream in excess of the amount 

 that will raise the temperature of the water more 

 than 5 F (based on the minimum expected flow for 

 that month). In lakes, the temperature of the 

 epilimnion should not be raised more than 3 F by 

 the addition of heat of artificial origin. 



(2) The normal daily and seasonal temperature 

 fluctuations that existed before the addition of heat 

 due to other than natural causes should be main- 

 tained. 



TABLE III-l 



[Provisional maximum temperatures recommended as compati- 

 ble witli tlie well-being of various soecies of fish and 

 their associated liiota] 



93 F: Growth of catfish, gar, vi^hite or yellow bass, 



spotted bass, buffalo, carpsucker, threadfin shad, 



and gizzard shad. 

 90 F: Growth of largemouth bass, drum, bluegill, and 



crappie. 

 84 F: Growth of pike, perch, walleye, smallmouth bass, 



and sauger. 

 80 F: Spawning and egg development of catfish, 



buffalo, threadfin shad, and gizzard shad. 

 75 F: Spawning and egg development of largemouth 



bass, white and yellow bass, and spotted bass. 

 68 F: Growth or migration routes of salmonids and for 



egg development of perch and smallmouth bass. 

 55 F: Spawning and egg development of salmon and 



trout (other than lake trout). 

 48 F: Spawning and egg development of lake trout, 



walleye, northern pike, sauger, and Atlantic 



salmon. 



Note. — Recommended temperatures for other species, not 

 listed above, may be established if and when necessary in- 

 formation becomes available. 



(3) The recommended maximum temperatures 

 that are not to be exceeded for various species of 

 cold-water fish are given in table III-l . 



Dissolved Oxygen 



The following environmental conditions are 

 considered essential for maintaining native popula- 

 tions of fish and other aquatic life. 



( 1 ) For a diversified warm-water biota, includ- 

 ing game fish, DO concentration should be above 



5 mg/1, assuming normal seasonal and daily 

 variations are above this concentration. Under 

 extreme conditions, however, they may range be- 

 tween 5 and 4 mg/1 for short periods during any 

 24-hour period, provided that the water quality 

 is favorable in all other respects. In stratified 

 lakes, the DO requirements may not apply to the 

 hypolimnion. In shallow unstratified lakes, they 

 should apply to the entire circulation water mass. 



These requirements should apply to all waters 

 except administratively established mixing zones. 

 In lakes, such zones must be restricted so as to 

 limit the effect on the biota. In streams, there must 

 be adequate and safe passageways for migrating 

 forms. These must be extensive enough so that the 

 majority of plankton and other drifting organisms 

 are protected (see section on zones of passage). 



(2) For the cold-water biota, it is desirable that 

 DO concentrations be at or near saturation. This 

 is especially important in spawning areas where 

 DO levels must not be below 7 mg/1 at any time. 

 For good growth and the general well-being of 

 trout, salmon, and their associated biota, DO con- 

 centrations should not be below 6 mg/1. Under 

 extreme conditions, they may range between 6 

 and 5 mg/1 for short periods provided the water 

 quality is favorable in all other respects and nor- 

 mal daily and seasonal fluctuations occur. In large 

 streams that have some stratification or that serve 

 principally as migratory routes, DO levels may 

 range between 4 and 5 mg/1 for periods up to 



6 hours, but should never be below 4 mg/1 at any 

 time or place. 



(3) DO levels in the hypolimnion of oligo- 

 trophic small inland lakes and in large lakes should 

 not be lowered below 6 mg/1 at any time due to 

 the addition of oxygen-demanding waste or other 

 materials. 



Carbon Dioxide 



According to our present knowledge of the sub- 

 ject, it is recommended that the "free" carbon 

 dioxide concentration should not exceed 25 mg/1. 



Oil 



Oil or petrochemicals should not be added in 

 such quantities to the receiving waters that they 

 will— 



33 



