XV 



PAGE 



1896 435 



Statistics 435 



Effect of recurrent floods 436 



Relation of production in channel and backwaters 437 



Effect of midwinter flood 438 



1897 441 



Statistics 441 



Relations of backwaters to channel 442 



Effect of prolonged low water 442 



1898 : 444 



Statistics 444 



The vernal pulse 446 



Comparison of channel and backwaters 447 



1899 449 



Statistics 449 



High winter-production 449 



Characterization of years 450 



Characterization of localities 451 



Relation of environmental factors to production 454 



Hydrographic conditions and plankton production 454 



Statement of the problem 454 



Effect of area 455 



Effect of depth 456 



Effect of age of the water 458 



Waters of recent origin 458 



Time requisite for development of plankton 459 



Impounding function of backwaters 460 



Current and rate of renewal 460 



Direct effect of current 460 



Effect of rate of renewal 461 



Net effect of run-off and renewal 462 



Fluctuations in hydrographic conditions 463 



Importance in fluviatile environment 463 



Cause of floods 463 



Effect of rising levels on channel 463 



Effect of rising levels in backwaters 464 



Recovery from flood 465 



Result of declining levels 465 



Production and total movement in levels 466 



High and low water periods in channel 466 



Levels and production in these periods during the year 467 



Summary 469 



High and low water in backwaters 470 



Effect of season in initial stages of flood-fall 470 



Temperature and plankton production 471 



Contrast of warm and cold seasons 471 



The vernal rise in temperature 472 



Seasonal distribution of production and temperatures 472 



