U.S. Watershed Nitrogen and Phosphorus Budgets for Streams and Lakes

2.64 million stream segments and 378,088 lakes have watershed and local catchment nitrogen and phosphorus budgets derived from a 30-year annual time-series (1987-2017). The dataset integrates the U.S. EPA's Next Generation National Nutrient Inventory with the StreamCat database using a tabular dasymetric apportionment process. It was developed by the U.S. Environmental Protection Agency.

Use Cases

• Modeling legacy agricultural surplus of phosphorus across watersheds to assess long-term water quality impacts.
• Correlating anthropogenic nitrogen inputs with downstream lake eutrophication risk using catchment-scale budgets.
• Analyzing spatial trends in agricultural surplus of nitrogen across ~2.64 million stream segments.
• Evaluating the relationship between natural phosphorus outputs and specific watershed characteristics over a 30-year period.

Strengths

• Covers 2.64 million stream segments and 378,088 lakes across the contiguous United States.
• Provides a 30-year annual time-series of nutrient budgets from 1987 to 2017.
• Includes major anthropogenic and natural inputs, outputs, and surplus metrics for both nitrogen and phosphorus.
• Workflow components are publicly available for replication and underwent spatial quality assurance.

Limitations

• The underlying county-level NNI data may mask sub-county variability in nutrient flows.
• The 2017 end date for the time-series may not reflect recent land-use or agricultural practice changes.
• Specific row counts and column details for the final derived datasets are not provided in the description.

Provenance

Source

U.S. Environmental Protection Agency.

Collection Method

Tabular dasymetric apportionment to downscale county-level NNI data, followed by the StreamCat accumulation framework.

Time Range

1987 to 2017.

Freshness

Data last updated on the platform in April 2026, though the source time-series ends in 2017.

Geography

Contiguous United States.