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Show tozoans, and 13 species of algae. ZoBell et al. ( 1937) worked on the bacterial flora of the lake. Recently, work has progressed toward understanding the interactions between organisms in the lake and the fate of pollution which enters the estuaries ( bays) of Great Salt Lake. Porcella and Holman ( 1972) reported on the relationship between nutrients, algal growth, and brine shrimp in the southern arm of Great Salt Lake. Coburn and Eckhoff ( 1972) and Meide and Nicholes ( 1972) report on the fate of pollution input to the Great Salt Lake estuaries. Still needed, however, is a complete ecological study of Great Salt Lake on a seasonal basis. Over the years, various government agencies ( federal, state, and local) and other groups have collected considerable quantities of data relating to the water resource system of Great Salt Lake. For example, records of lake levels have been maintained on a monthly basis by the U. S. Geological Survey since 1875. Even so, data deficiencies exist for many aspects of the system, and these inadequacies will become more apparent as the modeling process is continued. The LAKE COM Report ( 1973, p. 14) lists five specific areas of data deficiency pertaining to the lake system as follows: 1. Evaporation and rainfall. 2. Lake currents and general water movement patterns within the lake. 3. Geologic or subsurface conditions as indicated by seismic and gravity soundings. 4. The effects of high sulfur concentration levels in the lake brines on the extraction of other salts. 5. Groundwater conditions beneath the lake, including subsurface inflow rates. The preceding list is not intended to be exhaustive, but was a list of the major areas of data deficiency discovered by LAKE COM during their investigation. As part of this study a preliminary investigation was conducted to evaluate the adequacy of available data, defined in terms of spatial and temporal resolution requirements, as currently invisioned for the development of a management model of the lake system. The results of this survey are summarized by Table 3. The data for the various categories in the table have been rated as adequate, reasonably adequate, or not adequate for the three general areas of the Great Salt Lake basin ( watershed, nearshore, and lake). Model Formulation Model formulation is the step between the conceptual model and the working model indicated by Figure 3. The form of the model which is used is dependent entirely upon the requirements of the problem ( the objectives) and the data which are available for the study. Some insight into this process might be obtained by comparing a model to predict the effects of increased fresh water inflows on average lake salinity concentrations with a model developed to predict the fate of oil spills in the lake. In the case of the first model, brine concentrations at specific locations in the lake are not needed and so the spatial resolution can be gross. However, the second model requires a high degree of resolution in the space dimension. Thus, the requirements of the problem always are a prime consideration in model formulation and design, including the selection of appropriate time and space increments. The hierarchical- multilevel structure shown by Figure 7 is achieved through the combination of several models which become submodels in the hierarchical structure ( Haimes, 1973). Two layers are recognized in the hierarchical structure, namely, an information layer ( first layer) and a prediction and optimizing layer ( second layer). The second layer is composed of two levels: ( 1) societal and economic goals and considerations ( first level); and ( 2) political and decision- making considerations ( second level). The first layer represents the various physical aspects of the system, while the first dels for each of the six major uses of the lake system as listed earlier in this report. Clearly, any decision in the second level of the second layer which requires a change in some aspect of the physical system ( first layer) in order to accommodate a particular use in the first level of the second layer will create an adjustment throughout the entire system which will have a tradeoff affect on other societal activities. For example, a societal activity such as oil drilling might cause oil spills which will have an impact on the ecology of the lake, and in turn influence tourism and recreation. Thus, it is possible to view the second layer shown by Figure 7 as the cause and the first layer as the effect on the physical system, which in turn has a further effect on the second layer. The second level of the second layer represents the decision- making processes which coordinate and evaluate these cause and effect interactions and the trade- offs among the various societal uses and activities. At the lowest layer of the hierarchy ( first layer), the impacts of decisions and policies made by man and society on the Great Salt Lake system from a hydro- logical, limnological, and ecological point of view over a short, intermediate, and long time horizon are analyzed. 33 |