Mexican territory a few miles below Yuma, and
intended for irrigation of California south of the Sink, escaped
control, and the river, taking the canal as a new channel, recreated in
California a great inland sea--to the bed of which it had frequently
been turned formerly, for example, in 1884 and 1891--and for a time
practically abandoned its former course through Mexican territory to the
Gulf of California. But it was effectively dammed in the early part of
1907 and returned to its normal course, from which, however, there was
still much leakage to Salton Sea; in July 1907 the permanent dam was
completed. From the Black Canyon to the sea the Colorado normally flows
through a desert-like basin, to the west of which, in Mexico, is Laguna
Maquata (or Salada), lying in the so-called Pattie Basin, which was
formerly a part of the Gulf of California, and which is frequently
partially flooded (like Coahuila Valley) by the delta waters of the
Colorado. Of the total length of the Colorado, about 2200 m., 500 m. or
more from the mouth are navigable by light steamers, but channel
obstacles make all navigation difficult at low water, and impossible
about half the year above Mojave. The whole area drained by the river
and its tributaries is about 225,000 sq. m.; and it has been estimated
by Major J. W. Powell that in its drainage basin there are fully 200,000
sq. m. that have been degraded on an average 6000 ft. It is still a
powerful eroding stream in the canyon portion, and its course below the
canyons has a shifting bed much obstructed by bars built of sediment
carried from the upper course. The desert country toward the mouth is
largely a sandy or gravelly aggradation plain of the river. The regular
floods are in May and June. Others, due to rains, are rare. The rise of
the water at such times is extraordinarily rapid. Enormous drift is left
in the canyons 30 or 40 ft. above the normal level. The valley near Yuma
is many miles wide, frequently inundated, and remarkably fertile; it is
often called the "Nile of America" from its resemblance in climate,
fertility, overflows and crops. These alluvial plains are covered with a
dense growth of mesquite, cottonwood, willow, arrowwood, quelite and
wild hemp. Irrigation is essential to regular agriculture. There is a
fine delta in the gulf. The Colorado is remarkable for exceedingly high
tides at its mouth and for destructive bores.

In 1540, the second year that Spaniards entered Arizo