METHODS OF IRRIGATION.
There are three methods in use in supplying water to the arid lands. The first and the one most generally adopted for obvious reasons is the gravity system. The waters are impounded in lakes or artificial reservoirs and carried thence in large main canals, winding about the hills so as to secure a low uniform grade. Once established, no other force is needed but the usual flow of the water.
Another method resorted to when the gravity system is impossible is to pump the water from the big rivers into smaller reservoirs leading to the canals, the pumps being kept busy only during the months in which the water is needed. This method is quite successful, but requires a somewhat larger annual expenditure. It is being used in some extensive projects, the water being taken out of the Columbia river.
The third method is in securing the water by means of artesian wells. This method is naturally limited to small areas, the projects being undertaken by individual private owners. Several spots have been found in the arid belt where this method is successful.