SPARROW nutrient modeling: Great Lakes, Ohio, Upper Mississippi, Red River Basins (MRB3)

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SPARROW models for the Great Lakes, Ohio, Upper Mississippi and Red River Basins (MRB3) predict long-term average loads, concentrations, yields, and source contributions of nitrogen and phosphorus to the Great Lakes.

SPARROW (SPAtially Referenced Regressions On Watershed attributes) models track the transport of nutrients (particularly nitrogen and phosphorus) from local inland watersheds to regional, coastal waters by explaining spatial patterns in stream water-quality conditions in relation to human activities and natural processes.

Ongoing 2012 Midwest SPARROW Models

Figure showing phosphorus delivered from throughout the MRB3 basin

(a) Total phosphorus delivered to each of the Great Lakes, (b) total phosphorus deliveries to the Great Lakes, subdivided by each contributing source, and (c) total phosphous delivered from the entire MRB3 basin.

 

As part of Cycle 3 in the National Water-Quality Assessment Program, the capabilities of SPARROW will be expanded to include additional contaminants and to simulate changes in nutrient (or other contaminant) fluxes over time. Updated MRB3 SPARROW models are now being developed using nutrient input data from 2012 and further refined environmental-setting information. These models are being developed using smaller catchments (delineated using NHD Plus) to enable improved spatial descriptions of nutrient sources. The models will use updated nutrient loads from sites throughout MRB3 (and possibly Canada) and incorporate more data from smaller watersheds than the previous models.

 

2002 MRB3 SPARROW Models 

The Great Lakes, Ohio, Upper Mississippi and Red River Basins (MRB3; Upper Midwest) SPARROW models were based on 2002 nutrient-input data and included watersheds that deliver nitrogen and phosphorus to the Great Lakes (published in the Journal of the American Water Resources Association in 2011) and Upper Mississippi and Ohio River Basins.
 The 2002 MRB3 models indicated:

  • 2002 U.S. nutrient loadings to Lakes Michigan and Ontario were similar to those in the 1980s, whereas loadings to Lakes Superior, Huron, and Erie had decreased.
  • Highest loads were from tributaries with the largest watersheds, but the highest yields were from areas with intense agriculture and large point sources of nutrients.
  • Input from agricultural areas was a dominant source of nutrients, contributing 33-44% of the phosphorus and 33-58% of the nitrogen to each of the Great Lakes, except for areas around Superior with little agriculture.
  • Point sources were also important in some areas, contributing 14-44% of the phosphorus and 13-34% of the nitrogen to each of the Great Lakes.
  • Watersheds around Lake Erie contributed nutrients at the highest rate (similar to intensively farmed areas in the Midwest) because they have the largest nutrient inputs and highest amount delivered downstream, while those around Lake Superior contributed the least nutrients.
  • Nutrient deposition in lakes and reservoirs intersecting the tributaries to the Great Lakes was important in reducing nutrient delivery to the lakes.

Read the full press release on the 2002 MRB3 SPARROW model results.