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Show causeway, there were times that the entire lake was at saturation, similar to the north arm today. The brine shrimp survived, as we still have brine shrimp today. While we have brine shrimp in the south arm today and not in the north, the opposite was true during the 1980s high- water years. During that time, the north arm had a salinity of about 16 percent and the south arm was around 5 percent. The majority of the brine shrimp were living in the north arm. Having a two- salinity system lake may provide a means of protection to the brine shrimp as the lake fluctuates through its natural cycles. Work is presently ongoing by the GSL planning team, DWR and other private and public entities to learn more about the lake, its dynamic nature and its ecology. Additionally, USGS is updating its water salt balance model which can be used to determine the effects that different actions ( causeways, channels, pumping, dikes, etc.) would have on the lake as a whole. Future decisions on lake management will take into account the results of these studies. The driving concern for increasing the salinity of the south arm without changing the overall present nature of the lake is the historical salinity range. Breaching was done to lower the south arm relative to the north arm, not to relieve long- term flooding. Maintaining the north arm as a storage area ( higher than the south arm) was investigated and rejected due to cost, difficulty and overall disruption of the salinity and nature of the lake. The pumping project removes water from GSL, reducing the peak of high lake levels by increasing evaporation. Since the WDPP is already in place, a new dike, etc., to serve the same purpose as the pumps has not been recommended. None of the alternatives investigated in the 1980s could manage the level of the lake. The WDPP was selected to increase evaporation from the lake. A downward- grading, full- breach- depth channel would need to be constructed from the breach opening out into the south arm. The water salt balance model indicates that lowering the breach to lake bottom will have some positive effect on salinity distribution. Lowering the bottom of the breach, therefore, is being considered as part of the solution. The concept of re- plumbing and pumping a full return cycle would leave the minimum salt load possible in the West Desert if the project is used again. The alarm is based upon lack of brine shrimp populations in the north arm and declining brine shrimp in the south arm of the lake, a circumstance that can be remediated by addressing the salinity imbalance. The water- salt balance model being developed by USGS will determine if changes have occurred to the long- term cyclic nature of the lake's water chemistry. 288 |