streams
the property of the state, and a great body of irrigation law and
practice has grown up about this provision. The riparian doctrine does
not obtain in Colorado. In no part of the semi-arid region of the
country are the irrigation problems so diverse and difficult. In 1903
there were, according to the governor, 10 canals more than 50 m. in
length, 51 longer than 20 m., and hundreds of reservoirs. In 1899 there
were 7374 m. of main ditches. The average annual cost of water per acre
was then estimated at about 79 cents. The acres under ditch in 1902 were
greater (1,754,761) than in any other state; and the construction cost
of the system was then $14,769,561 (an increase of 25.6% from 1899 to
1902). There are irrigated lands in every county. Their area increased
8.9% in 1899-1902, and 80.9% from 1890 to 1900; in the latter year they
constituted 70.9% of the improved farm-land of the state, as against
48.8 in 1890. The land added to the irrigated area in the decade was in
1890 largely worthless public domain; its value in 1900 was about
$29,000,000. As a result of irrigation the Platte is often dry in
eastern Colorado in the summer, and the Arkansas shrinks so below Pueblo
that little water reaches Kansas. The water is almost wholly taken from
the rivers, but underflow is also utilized, especially in San Luis Park.
The South Platte is much the most important irrigating stream. Its
valley included 660,495 acres of irrigated land in 1902, no other valley
having half so great an area. The diversion of the waters of the
Arkansas led to the bringing of a suit against Colorado by Kansas in the
United States Supreme Court in 1902, on the ground that such diversion
seriously and illegally lessened the waters of the Arkansas in Kansas.
In 1907 the Supreme Court of the United States declared that Colorado
had diverted waters of the Arkansas, but, since it had not been shown
that Kansas had suffered, the case was dismissed, without prejudice to
Kansas, should it be injured in future by diversion of water from the
river. The exhaustion, or alleged exhaustion, by irrigation in Colorado
of the waters of the Rio Grande has raised international questions of
much interest between Mexico and the United States, which were settled
in 1907 by a convention pledging the United States to deliver 60,000
acre-feet of water annually in the bed of the Rio Grande at the Acequia
Madre, just above Juarez, in case of drought this supply being
dimi