Watershed‐Level Uncertainties: Implications for Phosphorus Management and Eutrophication

Abstract

Abstract Eutrophication is often the critical problem associated with surface waters having impaired water quality. Managing eutrophication in lakes and reservoirs typically involves the control of phosphorus inputs since it is often the limiting nutrient and because nitrogen and carbon are difficult to control. Management activities to address water quality impairment require a watershed‐level approach. However, uncertainty and stochasticity are ubiquitous in watershed‐level assessment and management. We describe and demonstrate a method for incorporating uncertainty analyses in watershed‐level modeling using Wister Lake in Oklahoma as an example. Natural stochasticity, parameter error, and error due to aggregation of data are quantified separately to allow for a comparison of the various sources of uncertainty in modeling activities. Parameter error was found to be the greatest contributor to overall output uncertainty. Several example management scenarios are presented to illustrate the utility and flexibility of including uncertainty quantification in watershed‐level management and decision making.