lERIGATIOlSr. 31 



to drop from terrace to terrace, leaving- a tiny reservoir at each stage, 

 from which water could be taken at need for irrigating small gf^rdens 

 and orchards. At the mouth of the ravine was a larger distributing 

 reservoir, with a dam of stone and masonr}^ for diverting- water into 

 the irrigation canals, which branched out over the lower lands beyond. 

 The safet}" of the larger dam was assured b}^ the presence of these 

 smaller reservoirs farther up the stream. By this method not onl}- 

 Avas water secured for irrigation, but the force of the current in times 

 of tlood was eftectually cliecked. For a roaring, nmdd}^ torrent, 

 sweeping all before it and carrj'ing awa}' great masses of the soil, 

 was substituted a gentle stream of clear water, incapable of destructive 

 erosion. 



Durinp- the long centuries of Arab domination most of these irriga- 

 tion works fell into ruin. Some, however, were patched up from 

 time to time, and were used by the Arabs to irrigate their small fields 

 and gardens. Soon after the French conquest the all-importance of 

 some provision for the artificial watering of the land was perceived, 

 and the construction of large storage and diversion reservoirs along 

 Algerian streams was begun. At first this work was done by the 

 engineer service of the French armv. 



COAST REGION. 



Irrigation in Algeria to-dav reaches its maximum development in 

 the larger vallevs and plains of the coast region. A number of 

 important irrigation districts have been established, and reservoirs and 

 canals have been constructed. At ]Marengo, on the Meurad, the first 

 storaee reservoir constructed bv the French was finished in 1857. 

 The. dam, built of earth, is 266 feet long and 90 feet high. The bar- 

 rage of the Cheurfas is built across the Sig, a short distance south of 

 St. Denis du Sig. It took the place of a Turkish dam which was 

 washed out in 1858. The present reservoir stores 2,100 acre-feet and 

 supplies water for the irrigation of 5,000 acres in winter and 2,000 

 acres in summer. A larger dam, 6 miles farther upstream, was com- 

 pleted in 1881. This dam was of masonrj', 98.4 feet high, 62.2 feet 

 thick at the base, and 13.1 feet thick at the top. The capacity. of the 

 reservoir was calculated at 11.600 acre-feet. On February 8, 1885, 

 the dam broke, carrying with it also that farther downstream. This 

 break is said to have been caused by the infiltration of water through 

 the rock around the dam. The foundation was of soft sandstone, in 

 many places hardly sufficiently indurated to warrant its being called 

 rock. The dam which was then built on the site of the older one is 

 on the same general plan as its predecessor, but instead of being built 

 on a straight line, the new portion is at an angle of 128 degrees with 

 the old work, the angle pointing downstream. The object of con- 

 structino- the daui in this w^av was to obtain a better foundation. It 



