Review of selected features of the Natural Systems Model and suggestions for applications in South Florida suggestions for applications in South Florida

The south Florida ecosystem has been greatly altered during the last 100 years. Drainage of the south Florida watershed began in the early 1880's, and by the early 1990's about 50 percent of the historic Everglades had been drained. In response to flooding and to provide water for a variety of human uses, a complex water-management system that includes levees, well fields, pumps, canals, and control structures was constructed throughout south Florida. Today, the south Florida ecosystem includes urban areas near the coast where nearly 4 million people live, intensively developed agricultural areas in the northern Everglades, and rangelands and wetlands throughout the region. The South Florida Water Management Model (SFWMM) was developed by the South Florida Water Management District (SFWMD) in the late 1970's and early 1980's to simulate the hydrology and the highly managed water system in an approximately 7,600-mi square mile area of south Florida. The effects of water-management activities, including ground-water pumping and canal control-structure operations, on time-varying ground-and surface-water conditions and on canal flows are simulated for selected land-use and water-management scenarios. The SFWMM is currently used by the SFWMD to evaluate feasible water-supply alternatives for projected land use and water demand in south Florida during the next 10-20 years.

A multimillion dollar, interagency effort is underway to restore significant portions of the south Florida ecosystem and to enhance the quantity, quality, and timing of freshwater flows to the remaining Everglades. A key component of this restoration effort involves returning hydropatterns (primarily frequency, duration, depth, and spatial extent of water inundation) at selected key locations in the Everglades to those which might have occurred in the natural system before human-induced changes altered the landscape and hydrology, or pre-drainage conditions. The Natural System Model (NSM) was developed to simulate the pre-drainage condition hydrology of south Florida. The NSM has been proposed as the "best available tool" for estimating hydropattern targets for restoration efforts. A study was being conducted to determine if the NSM can provide a reasonable simulation of south Florida hydrology for pre-drainage conditions, or the natural system, using recent climatic data. The absence of measured hydrologic, topographic, and vegetation data from the natural system for model construction and testing required the application of novel procedures to determine if NSM results are "reasonable". Only selected components and features of the model were being reviewed because of the limited resources and time available for the review.