CKAPTKR XXVI. 211 



with a central core cf sheet steel, in the form of plates riveted to- 

 gether 'and imbedded in masonry at bottom and on either side, con- 

 necting it with the bedrock abutments. The dam is 565 feet long, 

 20 feet wide on top, and contains about 140,000 cubic yards of rock. 

 It forms a reservoir covering 1,000 acres, and having a capacity of 42,190 

 acre-feet. The tributary watershed has an area of 100 square miles, but 

 with a run-off which cannot be relied upon to fill the reservoir with 

 frequency or regularity. It is necessary, therefore, to construct an 

 expensive conduit 11 miles long, from the Cottonwood, to bring a 

 supply to the reservoir. This conduit is to have a capacity of 220 cubic 

 feet per second, and will head at the Barrett dam, some 50 feet above 

 the base of the latter. 



The Moreno dam, which is still unfinished, will have an extreme 

 height of 150 feet, and is of similar character to the lower Otay dam, 

 except that the embankment is to be made watertight by a layer of 

 ;is=phalt concrete upon its upper face, connecting with a concrete toe 

 wall that extends to bedrock at the bottom of the dam. The elevation 

 of the dam is 3,100 feet above sea level, and has a tributary watershed 

 of 135 square miles, reaching to an extreme elevation of over 6,000 

 feet. The capacity of the reservoir at the 150-foot level is 46,733 acre- 

 feet, extending over 1,370 acres of surface. 



The Barrett damsite at the 160-foot contour has a capacity of 35,160 

 acre-feet. The dam to be erected is simliar in plan to the lower Otay. ^ 



These three reservoirs are to be united in one system, and supply 

 water for irrigating lands lying between San Diego and the Mexican 

 border, consisting of high mesas and valleys reaching back some ten 

 miles or more from the ocean. The rolling nature of the topography, 

 AS well as the economical use of water, will necessitate its conveyance 

 in pressure pipes of iron and wood. The city of San Diego, as well as 

 Coronado Beach, will receive at least a portion of its domestic supply 

 from these sources. 



THE BSCONDIDO DAM, 



In the northern portion of San Diego county lies one of the fairest 

 valleys of California, whose character is implied by its Spanish name, 

 Escondido, (hidden), surrounded and sheltered by rugged hills. Some 

 13,000 acres of this valley, including the town of Escondido, was or- 

 ganized into an irrigation district under the Wright law, and in 1894-95 

 constructed a notable dam in the adjacent mountains, to which was 

 torought a water supply from the San Luis Rey river, through a canal 



