8180

• UCREFRP Catalog Number: 8180
• Author: Hamilton, S. J.
• Title: Hypothesis of Historical Effects From Selenium on Endangered Fish in the Colorado River Basin.
• USFW Year: 1999.
• USFW - Doc Type: \
• Copyright Material: YES

Hypothesis of Historical Effects from Selenium

exceeding 40 years of age (produced in the early 1950s), with natural recruit-
ment undetected, and a population crash anticipated (Marsh, 1993). Similar
isolated populations of razorback sucker in reservoirs in the Salt and Gila river
basins in Arizona were initially abundant after impounding, but later disap-
peared in the 1950s as they aged (Hubbs and Miller, 1953; Minckley, 1973).
Dill (1944) noted in the lower Colorado River basin that Colorado
pikeminnow, bonytail, and razorback sucker were rare shortly before or after
1930 (he noted some observers claimed the decline occurred around 1925),
but in previous decades had been numerous. Deacon (1978) related that
declines in native fishes of the mainstream Colorado River were associated
with a very active period of dam building with concomitant increases in
irrigated agriculture, especially since 1930. Others believe the decline of the
Colorado pikeminnow, bony tail, and razorback sucker in the lower Colorado
River basin occurred in the 1930 to 1935 period following the completion of
Hoover Dam and the drought of 1934 (Minckley, 1973; Miller, 1961). How-
ever, Wiltzius (1978) and Bestgen (1990) noted the decline of razorback
sucker in the upper Colorado River basin predated the 1930s and the possible
influence of dams.

IRRIGATION ACTIVITIES IN THE GRAND AND GUNNISON RIVER
BASINS

Irrigation in the Colorado River basin was first undertaken by Native Ameri-
cans between A.D. 1000 and 1400 (Carlson and Muth, 1989). Settlement of the
Grand Valley in the upper Colorado River basin began in 1881, and the first
irrigation project, the private Grand Valley Canal, delivered water in 1886
(Butler et at., 1989). The federal Grand Valley Project was authorized in 1912,
and the first project water delivered in 1915. There are about 970 km of
irrigation drains in the Grand Valley (Butler et at., 1989). Virtually all the flow
in drainages in the Grand Valley Project area is from irrigation return flow and
drainage water (Butler et at., 1989). These drainages are ephemeral or inter-
mittent upstream of irrigated areas, but were perennial in the irrigated area
because of ground water recharge almost entirely from the irrigation systems.
Irrigation by settlers in the Uncompahgre and Gunnison river areas began
as early as the late 1880s. By 1890, about 12,140 ha of land were irrigated with
water from the Uncompahgre River (Butler et ai., 1991). One of the first five
irrigation projects undertaken by the federal Reclamation Service established
in 1902 was the Uncompahgre Valley Project (also known as the Gunnison
River Diversion or the Gunnison Tunnel Project). The 9.3-km tunnel was
authorized in 1903 and completed in 1910. In some years the entire flow of the
Gunnison River was diverted to the arid Uncompahgre Valley for irrigation,
with return flows entering the Uncompahgre River, which in turn reentered
the Gunnison River at Delta, CO. By 1909, before completion of the tunnel
and the expansion of irrigation in the Uncompahgre Valley, there were
274 km of associated canals, 644 km of laterals, and 330 km of drains in the
Gunnison Valley (summarized in Wiltzius, 1978). In 1958 there still were

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