No. 6 (1917) A NOTE ON TREATMENT OF SWAMPS, ETC. 163 



burrow pits where it is impossible to drain them, is either to fill 

 them in or treat them similarly to ordinary ponds by clearing 

 weeds, etc. and stocking with suitable fish. Fortunately at the 

 present time a large number of small fish find their way into some 

 of the pits and help to keep the larvae down. In some districts 

 however, these fish are netted out wholesale by fishermen using 

 casting nets of the smallest mesh. I would suggest that Govern- 

 ment adopt the following methods of dealing with these pits: — 



(1) If the levels permit, drain the pits off; if not, 



(2) fill in or, where they are extensive and hold water for 

 long periods, 



(3) link up each burrow pit by digging an open trench 

 between ihem, taking care that the sides of the trench are suffi- 

 ciently sloped to prevent the top soil falling in and blocking them. 

 Clear all pond weeds and debris and stock with suitable fish. 

 These trenches will permit the free access of fish to all the pits 

 and should any of the higher level depressions dry for a short 

 period re-stocking when they fill again, would occur naturally. 



(4) Prohibit all fishing in these pits. 



(5) When new tanks are being constructed or repairs being 

 made to old bunds make it compulsory to take the earth for the 

 bund from the bed of the tank and not from outside the bund. 



SHALLOW SWAMPS, ISOLATED POOLS, ETC. 



In dealing with shallow swamps, isolated pools, etc. in malaria- 

 infected districts, I would suggest that the best method would be 

 to trench the entire areas and drain off wherever possible. If it is 

 found impossible to drain a swamp in a malarial tract owing to 

 the nature of the country, then construct a pond at its lowest 

 level and drain the swamp by open trenches into the pond. This 

 pond would have to be kept clean similar to the others mentioned 

 above and stocked with suitable fish. It may be necessary to cross- 

 trench to get at all the little puddles of water held up ; but if 

 properly done and kept in order, it would, I think, certainly pay 

 in the long run. Many isolated pools which form from percolation 

 or from heavy rains could in most cases be drained off by these 



open trenches. 



OPEN WATER CHANNELS. 



Where water is taken by small open channels for irrigation 

 purposes, etc. in malaria-infected areas its course should be clearly 



