Uncertainty in critical source area predictions from watershed-scale hydrologic models

Area of Science:

• Environmental modeling
• Hydrology
• Water quality management

Background:

• Watershed models identify critical source areas (CSAs) for targeted conservation.
• CSAs export disproportionately high amounts of nutrients and sediment.
• Uncertainty in CSA simulations can hinder effective resource allocation.

Purpose of the Study:

• To assess uncertainty in critical source area (CSA) simulations.
• To evaluate the agreement of multiple models in identifying CSAs.
• To inform stakeholders about the reliability of CSA predictions.

Main Methods:

• Utilized an ensemble of four Soil and Water Assessment Tool (SWAT) models and one SPAtially Referenced Regression On Watershed attributes (SPARROW) model.
• Simulated CSAs for flow, phosphorus, nitrogen, and sediment in the Maumee River watershed.
• Quantified uncertainty by analyzing the variation in CSA locations across different models.

Main Results:

• Models showed agreement on a subset of CSA locations, suitable for confident targeting.
• Significant disagreement among models regarding CSA locations was prevalent.
• On average, only 16%-46% of identified CSAs were consistent across models.

Conclusions:

• Simulated CSA locations exhibit substantial uncertainty and variability across models.
• Comprehensive uncertainty analyses are crucial for reliable CSA identification in conservation planning.
• Ignoring model uncertainty can lead to inefficient targeting of conservation resources.