STORAGE RESERVOIRS. 105 



violent and destructive floods which are characteristic of other tributaries of the Po 

 are largely absent from those streams which flow through the lakes. 



" The flow of the Rhine in its upper source is said to be subject to much less varia- 

 tion than other streams similarly conditioned except as to natural reservoirs. 



"There are many thousands of other lakes scattered over the globe that act as 

 regulators of the streams which drain them, their efficiency in this respect being pro- 

 portional to the percentage which their areas bear to the tributary watersheds. Certain 

 it is that the aggregate influence of these reservoirs is very great, and the striking 

 difference often noted in the characteristics of the flow of streams with similar water- 

 sheds may largely be traced to this cause. 



Artificial Reservoirs. " While it is impracticable to imitate nature on the scale of 

 her own work in the construction of reservoirs, her example has nevertheless been 

 followed very extensively on a smaller scale. In fact, works of this character have been 

 built for a variety of purposes since the remotest antiquity. The storage of water for 

 feeding canals is a prominent example. The greatest reservoir systems yet constructed 

 have been designed to maintain the navigable condition of natural waterways. Many 

 reservoirs have had as a prominent reason for their construction the prevention of floods 

 in the valleys below them, although this has seldom if ever been an exclusive reason. 

 Storage of water for city supply, the development of power, and other industrial uses, 



is one of the most familiar of modern enterprises. Finally the field of irrigation, which 



i 



already presents many examples of great reservoirs, bids fair to outstrip all other fields 

 in the production of works of this character. In all these examples of reservoir con- 

 struction the purpose has been to correct the inequalities of nature to prevent the 

 rapid and destructive flow of rivers at seasons when not needed, and to augment and 

 re-enforce that flow when the need does exist. 



"One of the most extensive artificial systems ever built is to be found in Russia 

 at the head waters of the Volga and Msta rivers. The Volga River, the greatest in 

 Europe, 2325 miles long, and navigable nearly its whole length, rises in the province 

 of Tver, within 200 miles of St. Petersburg, and empties into the Caspian Sea in the 

 opposite extremity of European Russia. The Msta River has its sources interlaced 

 with those of the Volga, but flows in the opposite direction, and its waters find their 

 way, through the Volkhoff River, to Lake Ladoga, and ultimately to the Baltic Sea. 



"The sources of the Volga and Msta are in a flat, marshy, wooded country, about 

 665 feet above sea-level, covered with innumerable lakes, presenting conditions not 

 unlike those which prevail at the sources of the Mississippi River in our own country. 

 For a long period in the past these two river systems were connected by artificial 

 waterways, and the seaport of the upper Volga was upon the Baltic. The extreme 

 low water which is characteristic of the Volga and other Russian streams prevents 

 navigation in their natural condition except in seasons of high water. To ameliorate 

 this condition, advantage was early taken of the exceptional reservoir faqilities offered 

 by the lakes referred to, and dams of a cheap character were constructed across their 



