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Show Physical Subsystems Physical subsystems are the physical environment or setting and include basin geology, global and local climate, hydrology, lake level fluctuation, hydrodynamics and lake chemistry. The geologic setting and geography of the landscape creates this watershed and terminal basin. These influence the behavior of other physical components. Lake geomorphology which includes the erosion, transport and distribution of sediments and their patterns in the ecosystem are not well understood ( SRC, 1999b). Hydrologic processes cause fluctuations of lake volume, lake level and salinity. All are strongly influenced by each other and respond to regional and global climatic factors. ( See the " Hydrology" section.) Climatic forces drive watershed response and lake level fluctuations at multi- year, decadal and longer time scales. The ability to predict these changes is very limited. Resource managers deal with uncertainty in the long- term behavior of lake hydrology and at best can predict lake levels in the short term ( one to three years) along with some associated management implications and ramifications ( SRC, 1999b). Socioeconomic Subsystems Socioeconomic subsystems relate to human interactions that influence ecosystem response. This subsystem includes population, economic and other human- related interactions with a system. Salt extraction, mineral production, brine shrimp harvesting and oil and gas reserves are also important lake economic resources. Tourism and recreation are additional important lake uses. Rapid urbanization and agricultural expansion is occurring in portions of the GSL uplands and the watershed. This area contributes the vast majority of fresh water inflows to the lake. These human- induced impacts change the amount and temporal distribution of runoff into the lake, as well as the quality of runoff water. These changes affect lake level, water chemistry and ultimately other subsystem components. Management strategies may also influence lake level and chemistry, air and water quality. Upstream and watershed activities such as discharges, development and water allocation all interact with other lake ecosystems and all three conceptual subsystems. The political and economic arenas drive management actions within this subsystem. Activities within socioeconomic subsystems occur and affect the lake at seasonal to multi- year time scales. Biological/ Ecological Subsystems These subsystems focus on biological and ecological interactions. Lake level fluctuations, salinity and water quality affect the dynamics of the lake's ecosystems. This has implications for wetland habitats and the population dynamics of brine shrimp, brine flies and birds. There are further implications for tourism and commercial brine shrimp harvesting. Nutrient availability, air and water quality have ecological consequences. Lake managers have yet to fully understand these interactions and the affect of lake chemistry on biota ( some research is currently underway). The physical arrangement sets the stage for biological subsystems' ability to function. Temperature, light, salinity, •> 101 |