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Show inflow, although inflow exceeds evaporation during cooler, wetter weather cycles, and evaporation exceeds inflow during hotter, dryer cycles. All water which is diverted from the lake ( except the WDPP) is utilized for mineral extraction by evaporation and is included in the annual evaporation. At the average water elevation of 4200 feet above sea level, GSL has a surface area of 1,500 square miles, making it the fourth largest terminal lake in the world. GSL is hypersaline, with average total dissolved salt concentrations in its various arms ranging from about 8 percent to more than 26 percent. The average depth of the lake is approximately 14 feet, so that small changes in lake level either expose or inundate large areas of lake shoreline. For example, at a lake elevation of 4200 feet above sea level, the lake's waters cover 1,079,259 acres. At 4204 feet, lake waters inundate a total of approximately 1,223,000 acres. Seasonal and long- term fluctuations in lake level produce dramatic changes in the lake's shoreline. These fluctuations are an integral part of the lake ecosystem. Pumping from the lake would reduce peak elevations but allow natural fluctuations to continue. The physical configuration of the lake and its high salinity create a " buffering" effect on the rate of evaporation of the lake. In general terms, as the lake rises, it increases significantly in surface area and declines in salinity. These factors contribute to an increase in annual lake water evaporation, and tend to slow the rise of lake level. Conversely, when the lake level drops, the surface area diminishes and the salinity increases, reducing the total annual evaporation. The lake, therefore, has a natural mechanism to prevent drying up and has a tendency to slow its own rate of rise. It has been suggested that a one- time removal of water from the lake, while noticeable at the time of removal, will eventually " heal" itself through this buffering effect, returning to pre- removal elevations. Long- term increases in diversions will, however, produce long- term changes in lake level. Water Development Impacts on Lake Level Over the last 20 to 30 years, studies have attempted to define the effects of water development and other human- caused water use on lake level. The studies indicate that 100,000 acre- feet of annual depletion in the basin, the average level of the lake would be approximately one foot lower. The effect of this depletion on the lake elevation is greatest at low lake levels. The diversion of 100,000 acre- feet does not result in the depletion of 100,000 acre- feet if part of the diverted water returns to the lake. Water diverted for agricultural uses and for municipal and industrial uses ( M& I) is not entirely depleted, and significant quantities are returned to the system as return flows. Also an average increase of 100,000 acre- feet of inflow per year to the lake would raise the average lake level by approximately one foot. These studies have also shown that the lake would be approximately five feet higher without any human- caused depletions. It is expected that depletions to the inflow of GSL from historical sources will continue through water development on tributaries to the lake and other human- caused water uses. In the Jordan and Weber Basins, which have been 16 |