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

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Table 1. Historical events in the decline of endangered rash in the Colorado River basin. (continued)

Date Event

1935 Hoover (Boulder) Dam closed forming Lake Mead.

1936 Colorado River at Yuma, AZ, contained 4 ~g/L selenium (Byers el al., 1938).

1935-36 Elevated selenium in water at mouth ofUncomphagre River (220 ~g/L), mouth of Gunnison River (80 ~gIL), and Colorado

River near Grand Junction (30 ~gIL), whereas above irrigation activities the Colorado River contains I ~gIL (Williams and

Byers, 1935; Byers, 1936). Drains in Uncomphagre River valley contain 320-700 ~gIL selenium, and in Grand Valley

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contain 1,980-2,680 ~g/L (Byers, 1936).

1936

Selenium in water at Gunnison River mouth varies with irrigation activities and ranged from 5 to 55 ~g/L (Byers el a/.,

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1936, Anderson el a/., 1961). The San Juan River had 6 ~g/L at its mouth and 400-700 ~g/L in various drains, but I ~g/L

above irrigation activities (Byers el a/., 1938).

1936

73-178 kg per day of selenium loading from Gunnison River to Colorado River (Anderson el a/., 1961).

1942

Razorback sucker, Colorado pikeminnow, and bony tail rare in lower Colorado River (Dill, 1944).

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1946

Razorback sucker still unconunon in Gunnison River (Chamberlain, 1946; Hubbs and Mi1\er, 1953).

1950s

Razorback sucker abundant in Lake Mead.

Razorback sucker disappeared from reservoirs on the Gila and Salt rivers (Hubbs and Miller, 1953; Minckley, 1973).