OCR Text |
Show 121 cake1' theory, shown in Item 4, is most distressing because the dense layer of brine is several miles from shore around most of the Lake. In addition, the quality of the North Arm bottom layer brine may deteriorate to the sewage- like condition of the deep South Arm brine. The effects of creating additional openings in the causeway depend largely on the width and design of the opening or openings. It is certain, however, that additional openings would decrease the difference in elevation between the two arms of the Lake and would facilitate flow from south to north at depth, decreasing the difference in density. Increased southward flow at depth would increase surface flow of shallow low- density brines northward to maintain water inventory in the north. If these changes in flow rate were not significant in size, the present trend of the Lake might not be changed. If these changes in flow rate were large, it could provoke the stratification in the North Arm mentioned earlier ( Item 4). The Lake would be a " two- layer cake" with relatively fresh water on top and a stable dense brine layer at the bottom of both arms of the Lake. One possible solution to the causeway problem is the installation of one or two new causeway openings with controllable gates, permitting adjustments to be made as necessary. Item 5 shows one possibility with controllable gates. Table 24 shows the predicted effect of various sized openings in the causeway if the openings had been made in fall 1974. Elevations are predictions based on past elevation trends. In summary, the table shows that with a 200- foot opening the total depth of the causeway, the South Arm would be .2 feet lower than under existing conditions at the Lake's |