17 



head required for an effective scour ; in this ease nothing fur- 

 ther can be done to open the bar till the following year when 

 in May we have the coincidence of a low level of the lake and 

 high tides in the sea without. Under such conditions the bar 

 may be temporarily opened from the sea side by taking advan- 

 tage of the head of water provided by a high spring tide and 

 by building a groyne on the windward side of the projected 

 opening to check accumulation of sand and to direct more 

 effectively the scour of the first tidal water that enters the lake. 

 Such an operation is at once more costly and less effective than 

 when the opening be made in the reverse direction. It may 

 even fail entirely and at all times requires great care and judg- 

 ment to carry out successfully. The whole operations which 

 cost over Es. 5,000 are of temporary benefit only, as the bar 

 closes again by silting within a period varying from six weeks 

 to two months owing to the lack of flood- water scour to 

 counteract the silting tendency of the southerly winds and 

 current. 



Shrinkage of the water-level on the extraordinary scale 

 seen at periodical intervals in Pulicat lake, associated as it 

 doubtless is with a notable increase in salinitv, exercises 

 naturally a most baneful influence on all sedentary life, plant 

 as well as animal, within the normal limits of the lake ; if 

 the lake organisms be not dried up upon the general recession 

 of the water, they are almost certain to be killed by the 

 excessive salinity of the water in the pools remaining or by the 

 excessive heat to which thev are exposed. Only in the deep 

 channel near the bar can there be comparative safety. 



If the dangers associated with an abnormal fall in the 

 w r ater-level be survived, life within the lake finds another 

 danger in the great height to which floods may swell the lake 

 and reduce salinity far below the normal. Fortunately the area 

 of its w T ater-spread is so extensive that it can absorb and distri- 

 bute a great volume of flood water without a marked rise in 

 level. Unless the monsoon rains be particularly heavy, the 

 rise in the lake level is gradual and does not ascend much above 

 highest spring tide level when the bar is closed. As the water 

 became super-saline during the process of drying up during the 

 hot season, so the flood water of a moderate monsoon has the 

 effect of bringing salinity back to the normal. 



In exceptionally wet years when very heavy rain falls 

 continuously for days together, the moderating influence of the 

 great area of the lake is overcome and the level steadily rises 

 until such time as the head of water becomes so powerful as 

 to force open the bar or till an artificial cut through the beach 

 hastens this event. With the attention now given to ensuring 

 3 



