The effects of restricted circulation on the salt balance of Great Salt Lake, Utah

During the 1970-1972 water years a net load of dissolved solids of 0.26 billion tons moved from the south to north part of Great Salt Lake, Utah, through the causeway of the Southern Pacific Transportation Co. The load loss from the south part during the 1972 water year was only 0.01 billion tons, thus indicating that the salt balance between the two parts of the lake was near equilibrium for inflow conditions such as those of 1972. The future balance of dissolved-solids load in the lake for the existing (1972) causeway conditions depends principally upon the quantity of fresh-water inflow to the lake. For simulated inflow rates resulting in rising stages, the net dissolved-solids load increased slightly in the south part during a 10-year period. If the rate of rise of lake stage is great enough (greater than rates simulated for a 10-year period in a digital computer model), however, net load movement could be to the north part. And if the lake stage drops at the simulated rate for a 10-year period, the net effect would be a loss of 0.27 billion tons of dissolved-solids load from the south to the north part and the deposit of 1.08 billion tons of sodium chloride in the north part. The salt balance in Great Salt Lake can be changed by increasing the number of culverts or by widening the culverts in the causeway. The width of culvert opening necessary to bring the lake near chemical equilibrium depends upon the inflow conditions and desired salt balance. A culvert width of 500 ± 100 feet would be required to bring the dissolved-solids concentration in the south part to within about 85 percent of that in the north part and to limit precipitation of sodium chloride in the north part to less than 0.1 billion tons (for lake altitudes above 4,192 feet) for all the simulated inflow rates. A culvert width of 750 ± 150 feet would be required to bring the dissolved-solids concentration in the south part to within about 90 percent of that in the north part. Widening of culverts in excess of 500 feet would result in relatively little additional gain of net load of dissolved solids in the south part. The model was based largely on data collected during the 1971-1972 water years. The predictive 1Hydrologist, U. S. Geological Survey. accuracy of the model will be improved if the equations used in the model are refined on the basis of data collected in the future on the causeway and in the lake.