The figure on the left shows the estimated water depths and flow patterns under predrainage condition for a typical year. The map on the right shows the same for the current managed system. The mounding of water behind interior levees and the relative drying out of portions of WCAs and the ENP compared to the natural condition can be seen on the map on the right. Estimation of the environmental demands of the Everglades is a relatively difficult task. Typically, environmental demands are expressed in the form of desirable water depths, flows and hydroperiods. In order to determine the amount of water required to meet desired depths and hydroperiods, the infrastructure and its operations need to be predefined. Currently, the only authorized "environmental deliveries" are to ENP and they amount to about 400 thousand acre feet. The projected Everglades demands under restored conditions are estimated to be considerably higher. For the Restudy, the estimated "target demands" for the Caloosahatchee Estuary, St. Lucie Estuary, and Biscayne Bay in 1000 acre feet are 490, 550 and 630 respectively.

(Click on images below for a larger version.)

Spatial Distribution of Average Rainfall

Rainfall Deviations from Average in inches (Average = 52 inches) Monthly Distribution

(Above) Spatially averaged rainfall in South Florida is about 50 inches every year and about 70% of this rainfall occurs during the wet season months of June through October. The Lower East Coast (LEC) urban area receives about 10 inches more than the interior. (Below) The primary sources for meeting the increasing LEC urban demands are: rainfall, surface deliveries to canals from the regional system (LOK+WCAs), and uncontrolled seepage + groundwater flow from west to east.

(Above) The Regional system in the Lower East Coast (Lake Okeechobee and Water Conservation Areas) provides water to maintain the coastal canals, meet some of the urban demands, and control salt water intrusion along the coast. Surface water deliveries to the LEC urban area account for about 12% of the total urban demand. During drought periods, this demand can increase by as much as 100 percent. (Below) Agricultural demands in the system are primarily associated with the Lake Okeechobee Service Area which includes the Everglades Agricultural Area. This figure shows the magnitude of the demand to be met by Lake Okeechobee.

Supplemental Irrigation Demands on Lake Okeechobee

Sources: Natural System Model and the South Florida Water Management Model developed by the SFWMD Hydrologic Systems Modeling Division.