Document Type

Report

Publication Date

January 1984

Abstract

Problem Statement: Rising levels of the Great Salt Lake are severely impacting private and public property. in the private sector, the mineral industry, the railroad, and a number of recreation enterprises are suffering major damages. In the publi sector, the State of Utah is esperiencing large losses inflicted on roads and highways, waterfowl and related wildlife areas, and park and recreation facilities. The lake is partitioned by a semipervious railroad causeway into a north and a south arm with the sourth arm having about twice the water surface area and usually being two or three feet higher because it receibes nearly all the surface runoff from tributary rivers. in the last two years, the largest rainfall years of record (exceeded only the approximations made for 1866), record inflows, and record low evaporation rates have brought the largest historical rise in the lake water surface. Over this period, the sourth arm lake level rose to 4200.25 (June 1981), dropped to 4198.20 (October 1981), rose to 4200.85 (June 1982), dropped to 4199.80 (September 1982), and then rose to 4205.00 (July 1983). The south arm level dropped to about 4204.6, on August 15, but by January 15, 1984, the water surface reached an elevation of 4206.15. The north arm was about 2.5 feel lower. The lake level was the highest since 1887 when the lake was retreating from a high of 4207.7 in the previous year. The measured inflow of 5.3 million acre feet (maf) during the water year ending Sept. 1983, was the largest of record, surpassing estimated and more approximate values of 4.5 maf for 1872 and of 4.1 maf for 1909. The rise of 5.2 feet in 1983 surpassed the previously highest values of 3.4 feet in 1862 and 1907. in 1983, precipitation was 68 percet above normal, and evaporation was 86 percent of normal. Sequences from water years 1851 through 1983 of river inflows (Bear, Weber and Jordan), precipitation on the lake, evaporation from the lake, and annual high stages are given in Table 1. The flows are adjusted to represent present land and water use conditions, lake levels are historical readings on the south arm, and numbers given for the earlier years were not measured (except for two intermittent precipitation gages in the Salt Lake City area) but estimated through correlations and lake water blanace computations by the Utah Division of Water Resources and the Utah Water Research Laboratory. Objective planning of a strategy for dealing with this problem requires defining technically workable control methods, estimating their effects on probable lake lebels, translating effects on levels to effects on damges, and comparing the benefits of the damage reduction achieved with costs. This summary report presents estimates of probable lake levels under current conditions and the changes in these probabilities that could be expected with various lake level control alternatives (breaching the causeway, pumping into the western desert, and constructing reservoirs for irrigation development in the tributary basin). It also presents benfit estimates for these alternatives. Methodology is described in Bowles, James, and Chadwick (1984).

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