IRRIGATION, 33 



breaking of the dam, caused ])y a 6i-incli rain over a great part of the 

 watershed, the run-oti' in one night was more than three times the 

 capacity of the reservoir. 



Near the town of Kelizane a small masonry dam has been ))uilt 

 across the Mina River. This dam has a height of 45 feet above the 

 the bottom of the rocky gorge in which it is built. It was originally 

 planned to hold up a small storage reservoir, but this has become tilled 

 with sediment, and now the dam serves only for the direct diversion 

 of the water of the stream. The discharge of the Mina is small. 

 Though the canal system fed by this barrage covers an area of 20,000 

 acres, the land actually irrigated is not of large extent. The water of 

 this stream, when examined toward the end of July, 1902, was found 

 to carry 123 parts of soluble matter per 100,0»)0 parts of water. Of 

 this, 26 parts were ])icarbonates, 1 part carbonate, 60 parts chlorids, 

 and 36 parts sulphates. 



Another masonry work of importance is that across the Djidiouia 

 River near St. Aime, in western Algeria. It is 164 feet long, 55.8 

 feet high above the foundation, and 91.9 feet high, foundation included. 

 The base has a thickness of 36.1 feet, and the top 13.1 feet. The 

 reservoir has a capacity of 2,000 acre-feet, and is intended to irrigate 

 from 7,500 to 10,000 acres. 



Since it was built this reservoir has become almost completely tilled 

 with silt. In all reservoirs in Algeria the accunndation of silt has 

 given trouble, but only at St. Aime have attempts been made to 

 remedy the evil. M. Jaudin, a hydraulic engineer, has invented a 

 machine for stirring up and removing the silt. His apparatus consists 

 of a metal tu))e or conduit 20 inches in diameter, the lower end of 

 which penetrates the dam near its bottom. The free portion is kept 

 afloat ])y buoys and is attached by flexible joints to a floating scow. 

 The connections are made so as to allow the scow to float from side to 

 side of the reservoir, and the end of the pipe can be raised and low- 

 ered as desired. The diti'erence in level between the end of the 

 pipe projecting through the dam and that attached to the scow pro- 

 duces a strong current through the pipe. As the pipe is moved along 

 the mud is sucked into it and is carried below the dam. The clay 

 drawn into the pipe is found to be so well packed and so stitf that it 

 has to be cut out by a special cutting apparatus built like a steam screw. 

 In spite of the cutting apparatus, the water thus removed carried only 

 from 4 to 5 per cent of silt. The inventor claims that under favorable 

 conditions he can remove water containing 16 per cent of silt. The 

 expense of operating the apparatus is estimated at $35,000 a year, and 

 the cost of installation for a fairly large dam would be $540,000. The 

 inventor was under contract to remove the silt from this reservoir at 

 20 cents per cul)ic meter (15.4 cents per cubic yard). 



28932— No. 80—05 3 



