Modeling Phosphorus Dynamics in Everglades Wetlands and Stormwater Treatment Areas

Abstract

Longitudinal gradients in phosphorus (P) stored in the water column, vegetation, and soils develop in the wetlands where inflow P concentrations exceed background levels. Before the mid 1990's, the Everglades regional P gradient ranged from 100–200 mg L−1 in marsh inflows to background levels of 4–8 mg L−1. Subsequent implementation of P controls, including agricultural Best Management Practices and Stormwater Treatment Areas (STAs), has reduced the average inflow concentration along the northern edge of the Water Conservations Areas to approximately 30–50 mg L−1. Additional P controls are being implemented and further measures beyond those currently planned will be required to restore the entire marsh. The authors describe the evolution and application of relatively simple mass-balance models to simulate P storage and cycling processes along P gradients in the STAs and marsh. The models are practical tools with historical and future applications to designing P control measures involving source controls, water management, reservoirs, and STAs, as well as forecasting marsh responses to implementation of those control measures.