Modeling Lake Recovery Lag Times Following Influent Phosphorus Loading Reduction.

Area of Science:

• Environmental Science
• Limnology
• Water Quality Management

Background:

• Internal nutrient feedback loops can hinder lake restoration efforts.
• Phosphorus enrichment is a primary driver of eutrophication in freshwater lakes.
• Understanding recovery dynamics is critical for effective water resource management.

Purpose of the Study:

• To develop a mechanistic framework for modeling recovery lag times in phosphorus-enriched lakes.
• To estimate the time required for lakes to reach target phosphorus concentrations after external load reductions.
• To assess the impact of sediment phosphorus dynamics on lake recovery timelines.

Main Methods:

• A parsimonious, mechanistic model based on first-order kinetics in a two-compartment system.
• Incorporation of phosphorus storage and release from benthic sediments.
• Bayesian parameter modeling utilizing published data and prior lake calibration.

Main Results:

• Estimated mean lag time to 50% decline in water column phosphorus concentration is 13.1 years.
• Estimated mean lag time to 75% decline in water column phosphorus concentration is 39.0 years.
• Generated maps of estimated recovery times across a midwestern state and HUC-8 watersheds.

Conclusions:

• Internal phosphorus loading from sediments significantly influences lake recovery rates.
• The developed framework provides valuable insights for predicting lake response to reduced external phosphorus inputs.
• Results highlight the long-term commitment required for restoring phosphorus-impaired lakes across the continental United States.