1836.] 



Irrigation of the Delta of Tanjore. 



315 



of Seringham, and it seldom divided more favourably in the low freshes, 

 than for one half to flow down the Cauvery, and one half down 

 the Colleroon, while the cultivation under the former is about six times 

 the extent of that under the latter river. Thus it constantly happened 

 that while the Cauvery had one fourth of a proper supply of water, the 

 Colleroon had much more lhan it required; and often a much greater 

 quantity was flowing to waste to the sea by the Colleroon, than would 

 have been sufficient to complete the supply of water to Tanjore, and 

 this at a time when many thousand vaylies of paddy were perishing 

 for want of it. By means of this annicut and the sluices above men- 

 tioned, the water, in moderate and low freshes, can be divided in such 

 proportions as the principal Collector may require. There are many 

 sluices in the body of the annicut by which the sand can be let Off, and 

 by which also the distribution of the water can be partly regulated. 

 This work consists of three parts, into which it is divided by two is- 

 lands in the river.* The other new annicut is situated at the head of 

 the Vaddavaur above mentioned, which waters the talook of Mannar- 

 goody in South Arcot. It is intended to give that talook, and also the 

 talook of Chellumbrum, a more constant supply of water ; it is also 

 proposed to cut a channel from the south end, to convey an additional 

 supply of water to the north-east talooks of Tanjore; by thus obtain- 

 ing a complete control of the water in the lower part of the Colleroon, 

 no more need be allowed to pass the head of Seringham, than is abso- 

 lutely required for the cultivation under the last mentioned river, and 

 hence, in the low freshes, the water will all be distributed to the culti- 

 vation, and, in a good measure, divided in the proper proportions. 

 Canal sea end, 



The number of works of different kinds constructed in the Delta for 

 controlling and distributing the water, is roughly estimated as follows : 



• Large annicuts or wiers 4 



Smaller do. 6 



Sets of under-sluices , 5 



Large calingulahs 4 



Other smaller works of masonry, namely head sluices, 

 surplus sluices, aqueducts, small under sluices, an- 

 nicuts and calingulahs bridges, tunnels, by judgment, 



probably 10,000 



Embankments to the rivers upwards of 2,000 miles. 



Roads raised from 2 to 8 feet above the paddy field .. . 200 do. 



Irrigating and surplus channels probably not less than 20,000 do. 



* The northern division of this annicut has since been breached during a. fresh in the 

 river, but it can be repaired without difficulty ; the two other divisions remaining unin- 

 jured, a very great additional quantity of water has been thrown into Tanjore, and the 

 effects have been very important, 



