59 



the dam lietween April and July will be washed away. A lock has 

 been provided at the western end of the dam. 



This desig-n has proved to be the best for dams where the material 

 on which the foundation rests is not solid. It would doul)tless give 

 g-ood service in the Platte, Arkansas, and other American rivers where 

 the beds of the streams are similar to that of the Nile north of Assuan. 



The Assiut dam cost |1, 986,030. The stone was transported from 

 quarries farther up the river and the cement and ironwork were brought 

 from England. The Ibraimia Canal head gate, located on the west 

 side of the river just upstream of the dam, cost |370,(mX). It is of the 

 same general type as the dam except that it is provided with gates 

 which are designed to withstand the flood water. As reservoir con- 

 struction progresses on the upper reaches of the Nile, dams similar to 

 the one just completed at Assiut will have to be erected wherever large 

 canals are taken from the river. 



DRAINAGE. 



In Eg3"pt, as elsewhere, irrigation and drainage go together. The 

 Nile and the canals deposit material along their courses, and, after 

 running in one channel for a long period, this deposit raises the chan- 

 nel above the level of the surrounding country. The water ultimately 

 overflows their banks and runs across the low adjacent country, making 

 for itself shorter routes to the sea. This change in channels has taken 

 place many times since Egyptian history was first recorded. 



The delta is almost entirely separated from the sea l)y lakes which 

 are supplied by rainfall, by water escaping from the river, by water 

 from the canals, and l)y drainage from the holds. The boundary 

 between these lakes and the sea is maintained by w^ave action of the 

 Mediterranean. The process of draining them would be compara- 

 tively simple were it not that in some cases their surfaces are below sea 

 level. Before perennial irrigation was generally extended throughout 

 the delta, evaporation alone kept down the level of these lakes and 

 they did not injure the bordering farming lands. Many drains had 

 been dug, however, by the earlier irrigators. During the periods 

 when Egypt was occupied ])y Turks, Arabians, and others, who paid 

 but little attention to the condition of the farming class or to the suc- 

 cess of agriculture, many drains were a])andoned. while others were 

 used as canals. Large areas, once good farming lands, reverted to 

 salt marshes. It is with great difliculty that this land is ])eing 

 reclaimed at the present time. Into such a state of disorder had 

 things drifted w^hen the English took charge in 1S82 that many of 

 ■these early drains w^ere used for canals and cantds for drains. ]Many 

 thousand acres wdiich had previously been agricultural land reverted 

 to the original swampy condition. These are ])eing slowly reclaimed. 



