CONCEPTUAL ECOLOGIC MODELING IN REGIONAL ENVIRONMENTAL MANAGEMENT AND LAND PLANNING: A CASE STUDY OF LAKE TAHOE WATER COLOR TRANSPARENCY

The main value of conceptual ecologic modeling (CEM) for land use planners is for visualizing and understanding the factors affecting their problems. CEMs of land use problems are usually feasible and provide the general analysis planner's most often need.; I used CEMs to study the protection of lake water color and transparency. I developed a general then a detailed CEM of natural factors affecting those qualities. I estimated the areal distribution of nutrients (nitrogen and phosphorus) and potential suspended sediments on watersheds. I developed other detailed CEMs of nutrient and sediment release and delivery to the lake, their horizontal and vertical dispersal in it, lake nutrient cycling, their effect on water color and transparency via increased lake organic matter production, and suspended sediment deposition.; Management of nutrient stores and accumulation processes is needed to offset water quality damages caused by urbanization. Careful, periodic removal of biomass and litter deposits and quick reestablishment of forest cover are the only feasible methods.; CEMs for the lake revealed that capability classification based solely on a site's qualities is inadequate. It does not account for the antagonistic or synergistic effects of off-site conditions. Classification must include upslope and downslope conditions affecting the net consequences of land alterations. I recommend a classification scheme using ratings of above and below ground conditions affecting release and transmission of nutrients and sediments along the fall line on which projects are proposed. I include a rating of channel delivery efficiency from the base of fall lines to the lake.; The complexity of information in CEMs poses potential communication difficulties. Planners encourage public participation in their analysis process. They must also explain the reasons for their recommendations to decisionmakers. This problem can be readily overcome by using modern science communication techniques. The graphical nature of CEMs is inherently advantageous for communication.; CEMs are useful for organizing and synthesizing scientific information on many planning problems, for communicating understanding of possible consequences of alternative land use decisions and as stimuli of insights producing a comprehensive range of environmental management alternatives.