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Show waters of Farmington Bay and the main body are free to mix ( Gwynn, 1998a). Brine returning to the bay from bidirectional flow tends to resist mixing with the fresher water, and remains in a fairly coherent " tongue" which extends some distance to the south underneath the lighter Jordan River/ brine mixture. This forms a stratified brine condition within the central, deeper portions of Farmington Bay. The salt content of the upper Farmington Bay waters is maintained through vertical mixing of the tongue of denser, main body brine with the fresher water above it ( Gwynn, 1998a). Bear River Bay Bear River Bay is similar to Farmington Bay as a brine system. It is separated from the main body of the lake by the rock- fill causeway which contains a midpoint, bridged opening through which bidirectional flow takes place. The brine is stratified within the deeper portions of Bear River Bay. The upper layer of water contains 1- 2 percent salt. Below the upper layer of water lies a tongue of salty water which periodically moves into the bay by the bi- directional flow through the opening in the railroad causeway. The salinity of the lower brine tongue is similar to that of the adjacent main body of the lake. The thickness of the tongue of denser brine and that of the overlying less- saline water depends upon the rate of inflow into the bay and on prevailing wind conditions. South winds raise the level of the lake at the causeway, forcing the tongue of main body brine farther into the bay, making it thicker. North winds lower the level of the south arm at the causeway, causing the brine to extend a shorter distance into the bay, and it becomes thinner. When the tongue of main body brine thickens and extends farther into the bay, the overlying fresher brine layer thins ( Butts, 1998). Gilbert Bay The salinity ( total- dissolved- solids) of Gilbert Bay varies inversely with lake elevation, and since 1966 has fluctuated from a high of 250 grams/ liter in 1966 ( approximately 21 percent salinity) to a low of about 50 grams/ liter in 1986 ( approximately 5 percent total salinity). The south arm of the lake receives nearly all of the freshwater inflow to the lake, including flows from the Jordan, Weber and Bear Rivers, and numerous, minor, east- and south- shore streams. ( See Figure 3.) From 1966 until about mid- 1991, the south arm of the lake was density- stratified into two brine layers. A dense, turbid, hydrogen sulfide- laden brine extended from an elevation of about 4180 feet to the bottom of the lake. A less dense, clearer, odor- free brine extended upwards from about 4180 feet in elevation to the surface. The two brines were separated by a relatively sharp transition zone. The deeper, denser brine layer disappeared in mid- 1991, after the high- water years ( 1983- 87). During the 1980s, the surface elevation of the lake rose from about 4200 feet to nearly 4212 feet by 1986- 87. The disappearance of south- arm stratification is probably due to diminished north- to- south return flow through the causeway brought about by the apparent changes in the hydraulic conductivity ( permeability) in the northern railroad causeway ( See Appendix I). Since mid- 1991, brines of the south arm have been thoroughly mixed from top to bottom. This may have been caused by the addition of fill 44 |