TESTIMONY OF DR. LARRY J. PAULSON DIRECTOR, LAKE MEAD LIMNOLOGICAL RESEARCH CENTER UNIVERSITY OF NEVADA, LAS VEGAS PRESENTED TO HOUSE COMMITTEE ON INTERIOR AND INSULAR AFFAIRS 8 SEPTEMBER, 1983, NEEDLES, CALIFORNIA Mr. Chairman and Members of the Committee: I am a Research Professor and Director of the Lake Mead Limnological Research Center at the University of Nevada, Las Vegas. My research specialty is limnology--the study of physical, chemical and biological properties of freshwater lakes and reservoirs. I work full-time studying the limnology in reservoirs on the Colorado River. I have conducted numerous limnological investigations for the Bureau of Reclamation, Environmental Protection Agency, Fish and Wildlife Service and state agencies. The principal purpose of my research is to assist the agencies in solving various management problems of the Colorado River. I have knowledge of the matters before the committee and wish to offer the following statements to assist in your investigations of the flooding in the Colorado River. The historical runoff data for the Colorado River represent one of the most complete records available for any river system in the nation. Runoff records date back to 1878 for Yuma and to 1895 for several other locations (1,2). Runoff estimates have been reconstructed for most locations from high water marks or other river gages and provide fairly accurate records for the past 100 years (3). The highest spring runoff known to have occurred in the Colorado River was in 1884 (4). Estimates place the April-July natural (virgin) runoff at 30.2 million acre-feet (Figure 1). The natural runoff is that which would have occurred without depletions or regulation. Natural spring runoff was estimated at 18.021 million acre-feet in 1917, 17.007 million acre-feet in 1920 and 17.000 million acre-feet in 1983 (Figure 1). Natural spring runoff ranged from 15-17 million acre-feet in 1907, 1909, 1914, 1921, 1952 and 1957 (Figure 1). There were several years where it ranged from 13-14 million acre-feet (Figure 1). In 1983 the actual flow at Lees Ferry during April-July was 9.095 million acre-feet. About 5.5 million acre-feet of runoff was stored in upstream reservoirs for a total of 14.6 million acre-feet (Figure 1). There are several years on record when the measured spring runoff either exceeded or was comparable to that in 1983 (Figure 1). Spring runoff in 1983 clearly was not a record. Bureau officials now estimate that natural runoff for the water year will be a record at 24.7 million acre-feet. The 1983 water year runs from October 1982 through September 1983. Depletions in the upper basin and runoff in August and September will have to be high in order for annual runoff to reach 24.7 million acre-feet. Even if the projection is correct, it will still not be a record. 1884 1907 1909 1914 1917 1920 1921 1929 1941 1942 1952 1957 1965 1983 H-NATURAL -MEASURED Figure 1. Natural and measured spring (April-July) runoff in millions of acre-feet at Lees Ferry. Measured runoff for 1965 and 1983 adjusted for storage in upstream reservoirs. (Natural runoff estimates from reference (8); measured runoff from U.S. Geological Survey Water Supply Paper Nos. 1313, 1733 and 1925; data for 1983 based on U.S. Bureau of Reclamation Lower Colorado Region provisional records) Spring runoff in 1884 was higher than the annual runoff estimated for 1983. However, at this stage, it is pointless to further argue over record runoff. It was not record spring runoff, or record annual runoff that caused the flooding. The volume in Lake Powell exceeded the level of the spillways on 8 June, 1983 (Table 1). The combined Lake Powell inflow was 5.172 million acre-feet during 1 April to 8 June (Table 1). The maximum mean daily inflow of 111,500 cfs into Lake Powell occurred on 28 June. By then, water levels were 6.7 feet above the spillways and discharges from Glen Canyon Dam were averaging about 85,000 cfs. The volume in Lake Mead exceeded the level of the spillways on 3 July. The inflow to Lake Mead from Grand Canyon during 1 April to 3 July was 6.130 million acre-feet (Table 1). Discharges from Hoover Dam were increased to 38,000 cfs on 16 June and have averaged about 40,000 since that time. Lake Powell was in flood operations by early June at a spring inflow of about 5 million acre-feet. Peak monthly runoff in the Colorado River usually occurs during June, as it did in 1983. The June inflow into Lake Powell was 5.361 million acre-feet, and another 3.574 million acre-feet entered the reservoir in July (Table 1). The June and July inflows were not particularly unusual, and in fact were very similar to those experienced as recently as 1957. The measured June inflow into Lake Mead from Grand Canyon in 1957 was 5.541 million acre-feet and July was 4.033 million acre-feet (5). |