Fig. 18.—Canal and Station on Payette River, Idaho.
From these illustrations it may be seen that in many cases, in comparatively level country, a water-power can be fully developed only by means of canals or pipe lines, and the generating stations cannot be located at the points where the water is diverted.
Thus far the cases considered have been only those with moderate heads and rather large volumes of water. In mountainous country, where rivers are comparatively small and their courses are marked by numerous falls and rapids, it is generally necessary to utilize the fall of a stream through some miles of its length in order to effect a satisfactory development of power. To reach this result, rather long canals, flumes, or pipe lines must be utilized to convey the water to power-stations and deliver it at high pressures.
In cases of this kind the cost of the canal or pipe line may be the largest item in the power development, and it may be an important question whether this cost should be reduced or avoided by the erection of several small generating plants instead of one large one. California offers numerous examples of electric-power development with water that has been carried several miles through artificial channels. An illustration of this class of work exists at the Electra power-house on the bank of the Mokelumne River, in the Sierra Nevada Mountains. Water is supplied to the wheels in this station under a head of 1,450 feet through pipes 3,600 feet long leading to the top of a near-by hill. To reach this hill the water, after its diversion from the Mokelumne River at the dam, flows twenty miles through a canal or ditch and then through 3,000 feet of wooden stave pipe.
Another example of the same sort may be seen in the power-house at Colgate, on the North Yuba River, in the chain of mountains above named. Water taken from this river passes through a wooden flume nearly eight miles long to the side of a hill 700 feet above the power-house, and thence down to the wheels through steel and cast-iron pipes, five in number and thirty inches each in diameter.
Even with long flumes, canals, and pipe lines, it may be necessary to locate a number of generating stations along a single river of the class now under consideration in order to utilize its entire power. Thus on the Kern River, which rises in the Sierra Nevada Mountains and empties into Tulare Lake, two electric power-stations are under construction, and surveys are being made for three more. Of these stations, the one at the lowest level will operate under an 872-foot head of water, and this water, after its diversion from the river, will pass through twenty-one tunnels, with an aggregate length of about ten miles, and through six flumes mounted on trestles and having a total length of 1,703 feet.
Next up-stream is a station near the point where water is diverted for the plant just named. This second station will work under a head of 317 feet, and water for it will come from a point farther up-stream by canals, tunnels, and flumes, with an aggregate length of eleven and one-half miles. At three points still higher up on this river it is the intention to locate three other power-stations by conducting the water in artificial channels, about twelve and one-half, fifteen, and twenty miles in length respectively.
Farther south in California, on the Santa Ana River and Mill Creek, extensive power developments on the lines just indicated have been carried out. On Mill Creek, about six miles from the city of Redlands, is an electric station operating under a head of 530 feet, with water in part diverted from the stream a little less than two miles above and brought down through a steel pipe 10,250 feet long and thirty inches in diameter. This pipe line also takes water from the tail race of another generating plant at its upper end. With some additions and modifications, the station just described is the famous Redlands plant, built in 1893, and believed to be the first for three-phase transmission in the United States.
