The Grand Coulee Dam

Abstract

THE Columbia River in the United States is second in size only to the Mississippi. Owing to the fact that its source is high in a region of melting enows in the mountains of western Canada and Montana, its discharge is more continuous than that of all the arid regions of the west and the middle west combined. In an article in the Scientific American of April, Grace Kirkpatrick gives an interesting account of the Grand Coulee (Grand Valley) dam which engineers are now busily constructing. In prehistoric times the Columbia River, then much larger than it is to-day, was dammed by a glacier, and the torrents of water which poured through the high cliffs bordering the river flowed down and formed the Grand Coulee. The walls of the valley are in some places 1,000 feet high. The upper 20 miles of the river are being closed with dams at each end to form a huge reservoir. The Columbia River sweeps across the State of Washington and forms for many miles the border between Washington and Oregon. On the plateau above its canyon-like banks are millions of arid acres known as the Columbia Basin which if suitably irrigated would be one of the most fertile lands in the world. The dam is being built in two units, the high dam and the low dam. The latter is exclusively a power development while the high dam will be used for power, irrigation, storage and navigation development. The dam will raise the waters of the Columbia so that they can be pumped into the reservoir of the Grand Coulee and will then flow over the parcned acres of the Columbia Basin. The blocking of the river will create the largest artificial lake in the world. It is 151 miles long and will extend into Canada. The spillway in the centre of the high dam will be 1,800 feet long and no less than 325 feet high.