A Spatially Explicit Model for Estimating Annual Average Loads of Nonpoint Source Nutrient at the Watershed Scale

Tao Zhang

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


The overloaded nonpoint source (NPS) nutrients in upper streams always result in the nutrient enrichment at lakes and estuaries downstream. As NPS pollution has become a serious environmental concern in watershed management, the information about nutrient output distribution across a watershed has been critical in the designing of regional development policies. But existing watershed evaluation models often encounter difficulties in application because of their complicated structures and strict requirements for the input data. In this paper, a spatially explicit and process-based model, Integrated Grid's Exporting and Delivery model, was introduced to estimate annual in-stream nutrient levels. Each grid cell in this model was regarded as having potentials of both exporting new nutrients and trapping nutrients passing by. The combined nutrient dynamics of a grid is mainly determined by the grid's features in land use/land cover, soil drainage, and geomorphology. This simple-concept model was tested at some basins in north Georgia in the USA. Stations in one basin were used to calibrate the model. Then an external validation was employed by applying the calibrated model to stations in the other neighbor basins. Model evaluation statistics implied the model's validity and good performance in estimating the annual NPS nutrients' fluxes at the watershed scale. This study also provides a promising prospect that in-stream annual nutrient loads can be accurately estimated from a few public available datasets.

Original languageEnglish (US)
Pages (from-to)569-581
Number of pages13
JournalEnvironmental Modeling and Assessment
Issue number6
StatePublished - Jun 2010
Externally publishedYes

Bibliographical note

Funding Information:
Acknowledgements Portions of this research were funded by the Graduate Scholarship at the Florida State University. Thanks to X. Yang, V. Mesev, J. Elsner, J. Stallins, and B. Hu for their valuable advice and contributions to the development of this model. The comments of M. Winsberg greatly improved the manuscript. The anonymous reviewers also provided me thoughtful and helpful reactions.


  • Annual Nutrient Load
  • IGED
  • Nonpoint Source Pollution
  • Spatial and Temporal Scales
  • Spatially Explicit Model
  • Upper Chattahoochee River Basin
  • Watershed Scale


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