1922.] Fauna of the Chilka Lake : Observations in liambiia Bay 681 



level is that the water of low salinity, hitherto confined at the southern end, spreads 

 further north. In course of time the level sinks to a minimum and subsequently, 

 under suitable conditions of wind and tide, volumes of salt water enter from the 

 sea and entirely fill the outer channel. This in 1914, had already taken place before 

 the month of February. Under normal conditions the waters of the main area 

 probably rise in salinity owing to successive inflows from the Bay of Bengal, until a 

 maximum is reached in July. By August the monsoon floods have commenced, the 

 water level rises rapidly and a repetition of the annual cycle begins." 



In order, therefore, to obtain so far as was possible an insight into the annual 

 changes that take place in the salinity of the water in Rambha Bay, two series of 

 observations were carried out, in August, 1919, and in April, 1920, respectively. 

 These months were selected as being the most likely periods in which to get the 

 desired information, since in August the influx of fresh water would be causing a rise 

 in level and a fall in salinity, while in April, there should be a large influx of salt water 

 entering the lake from the sea. 



In the following pages I propose first to consider these two periods separately 

 and afterwards to compare and correlate the results obtained. 



I. Observations in August, 1919. 



During the early part of my visit to the Chilka Lake, from August nth to 16th, 

 1919, the local conditions were more or less constant and, on the whole, the wea- 

 ther was fine with light winds from the south and south-west; there were 

 occasional light showers of rain and a somewhat heavier shower, accompanied by a 

 north-easterly wind, occurred on August 16th, and lasted for about an hour. On 

 August 17th, however, there was a heavy storm with strong wind from the north- 

 east which caused a considerable rise in the height of the lake. The reverse effect, 

 of a strong wind from the south-west lowering the level of the water in Rambha 

 Bay, has been recorded by Annandale and Kemp (loc. cit., p. 11). Unfortunately I had 

 no means available of measuring the actual amount of the rise of level that 

 occurred, but it must have been several inches, and simultaneously the waves raised 

 by the wind must have caused a considerable disturbance and admixture of the 

 water in the upper levels. Obviously then observations taken after this date (August 

 17th) are not comparable with those recorded earlier, and I have therefore considered 

 them separately. 



Wherever it was found possible, three observations — on the surface, at 5 feet 

 and 10 feet depth — were made at each station, but where the shallowness of water 

 did not permit of observations at this latter depth, I took two observations, at the 

 surface and at 6 feet depth respectively, and the results obtained are given in extenso 

 in the Appendix, Table 1. As my investigations were of necessity made on different 

 days and therefore under slightly different conditions of temperature, etc., it might be 

 argued that the results obtained are, in view T of the shallowness of the water in 

 the Bay and the varying effects of radiation and conduction of heat through the 

 different layeis of water, not strictly comparable with each other. I have, therefore 



