80 THE IRRIGATION AGR. 



United States where agriculture is carried on by means of irrigation, 

 as to the natural advantages for the storage of water for irrigation 

 purposes, with the practicability of constructing reservoirs, together 

 with the capacity of streams and the cost of construction and capacity 

 of reservoirs, and such other facts as bear on the question of storage 

 of water for irrigation purposes." 



In October, 1888, an appropriation was made for the purpose of in 

 vestigating the extent to which the arid region of the United States 

 can be redeemed by irrigation and for the selection of sites for reser- 

 voirs and other hydraulic works necessary for the storage and utili- 

 zation of water for irrigation and the prevention of floods and over- 

 flows. 



In an act approved August 30, 1890, it was specified that reservoir 

 sites heretofore located or selected shall remain segregated and reserved 

 from entry or settlement, and reservoir sites hereafter located or 

 selected on public lands shall in like manner be reserved from the 

 date of the location or selection thereof. In a subsequent act, ap- 

 proved March 8, 1891, it is provided that the reservoirs shall be re- 

 stricted to the land actually necessary for the construction and main- 

 tenance of reservoirs. 



By the act of August 18, 1894, a specific appropriation was made, 

 "for gaging the streams and determining the water supply of the 

 United States, including the investigation of underground currents 

 and artesian wells in arid and semi-arid sections." In later acts there 

 has been included the preparation of reports upon the best methods of 

 utilizing the water resources of these sections. 



MAPS AND ESTIMATES. 



Under the authority thus given work has been carried on syste- 

 matically by the Division of Hydrography, and each year reservoir 

 sites have been discovered and surveyed. In the discovery of res- 

 ervoir sites assistance is given by the Division of Topography in the 

 course of the preparation of contoured maps showing elevations of the 

 surface. These maps also furnish information concerning the extent 

 and character of the catchment areas tributary to various streams. 



Differences exist in the character of the surveys in various locali- 

 ties. In many places only a reconnoissance has been made, this being 

 sufficient to develop the fact that a suitable basin exists. At the 

 other extreme, detailed surveys of some localities have been made, 

 showing by contours at 1-foot or 5-foot intervals the entire basin to be 

 flooded, and also on a larger scale the site of the proposed dam. Bor- 

 ings to bed rock have also been made the Survey being in possession 

 of two complete diamond drill machines with all the equipment for 

 work of this character. From the maps and borings estimates of the 

 cost of construction have been prepared, and plans drawn showing the 

 character of structure proposed, the information being complete for 

 making an appropriation for construction. As a matter of course, if 



