The most serious problem with which engineers have to deal in the irrigation of arid land from a turbid river is the getting rid of silt, and this problem is a particularly difficult one in the Imperial Valley, owing to the immense amount of sediment that the irrigating water contains. The Colorado River, until after it passes the Grand Cañon, is almost everywhere a swift, turbulent stream, with great eroding capacity. As Mr. E. C. LaRue has said, in a brief but graphic description of it, “When the snows melt in the Rocky and Wind River Mountains, a million cascade brooks unite to form a thousand torrent creeks; a thousand torrent creeks unite to form half a hundred rivers beset with cataracts; half a hundred roaring rivers unite to form the Colorado, which flows, a mad, turbid stream, into the Gulf of California.” (“Colorado River and Its Utilization,” a Geological Survey report, Government Printing Office, Washington 1916.) Such a river, naturally, dissolves the earth and gnaws the rocks over which it tears its way, and takes up millions of tons of solid matter, in the shape of gravel, sand and finely pulverized soil. This great volume of sediment, when finally dropped, not only tends to change the river’s course by creating bars at or near its mouth, but gradually fills up the irrigating ditches and canals and thus lessens their carrying capacity. A single day’s supply of water for the Imperial Valley contains silt enough to make a levee twenty feet high, twenty feet wide, and one mile long. (Imperial Valley Press, July 25 1916). If this silt is not dredged out, sluiced out, or collected in a settling basin, it eventually raises the beds of the canals, fills the ditches, and chokes up the whole irrigation system. The managers of the California Development Co. had difficulty, almost from the first, in keeping their waterways open. As more and more land was brought into cultivation, more and more water was required, while the silting up of the canals lessened the ability of the company to meet the constantly increasing demand. There was a shortage as early as the winter of 1902-3; but the situation did not become serious until the following year, when the main canal, for a distance of four miles below the intake, became so silted up that it could not possibly carry the volume of water that was imperatively needed. An attempt was made to remedy this state of affairs by putting in a waste-gate, eight miles below the intake, for the purpose of sluicing out the channel in time of high water.