I am posting this six-year old open-access JAWRA paper by USGS folks Dale M. Robertson and David A. Saad because it has had a lot of activity in the past few days. Wonder why? See Elaine Hanford's comment below for one explanation, and then there's the 'infamous' western Lake Erie toxic algae blooms.
Below is the full citation and abstract. Click here or on the title to gain free access to the paper.
Robertson, Dale M. and David A. Saad, 2011. Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models. Journal of the American Water Resources Association (JAWRA) 47(5):1011-1033. DOI: 10.1111/j.1752-1688.2011.00574.x
Abstract: Nutrient input to the Laurentian Great Lakes continues to cause problems with eutrophication. To reduce the extent and severity of these problems, target nutrient loads were established and Total Maximum Daily Loads are being developed for many tributaries. Without detailed loading information it is difficult to determine if the targets are being met and how to prioritize rehabilitation efforts. To help address these issues, SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed for estimating loads and sources of phosphorus (P) and nitrogen (N) from the United States (U.S.) portion of the Great Lakes, Upper Mississippi, Ohio, and Red River Basins. Results indicated that recent U.S. loadings to Lakes Michigan and Ontario are similar to those in the 1980s, whereas loadings to Lakes Superior, Huron, and Erie decreased. Highest loads were from tributaries with the largest watersheds, whereas highest yields were from areas with intense agriculture and large point sources of nutrients. Tributaries were ranked based on their relative loads and yields to each lake. Input from agricultural areas was a significant source of nutrients, contributing ∼33-44% of the P and ∼33-58% of the N, except for areas around Superior with little agriculture. Point sources were also significant, contributing ∼14-44% of the P and 13-34% of the N. 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 delivery ratio.
I have long been intrigued by the SPARROW model, which is used in the Robertson and Saad paper. A model named after a small bird? It actually is an acronym: SPAtially Referenced Regression On Watershed attributes.
When I served on a USGS NAWQA Program committee SPARROW was discussed a lot because it was being used to track nutrients (nitrogen and phosphorus) from the Mississippi River basin to the Gulf of Mexico. As seen from the maps SPARROW can be used on a very large scale. Although it is an empirical model it can used physically-based algorithms such as those to describe chemical fate and transport.
About 10 years ago I was attempting to use SPARROW to simulate chemical fate and transport in the Kura-Araks basin of the South Caucasus. Did not have quite enough data. But it was a useful exercise in terms of understanding how the model worked.
I would still like to give it another try one of these days.
Want to see more SPARROW papers? Here is a featured collection of open-access papers from JAWRA.
Enjoy!
"Not everything that is faced can be changed, but nothing can be changed until it is faced." - James Baldwin (via @GreatestQuotes)
Perhaps the interest arises from the latest findings on the "Dead Zone" in the Gulf of Mexico marking the extent of hypoxia in the Gulf of Mexico is about 50 percent larger than average
• https://arstechnica.com/science/2017/08/gulf-of-mexico-dead-zone-is-largest-on-record/
Posted by: Elaine J Hanford | Thursday, 03 August 2017 at 08:24 PM