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Richard Coupe:

Today we're going to talk about the National Water-Quality Assessment program and part of a component of that is our Agricultural Chemical Transport study. This is a study looking at the effects of agriculture on water quality at seven different sites across the country. And today specifically though we're going to being talking about an area in Northwest Mississippi, our Mississippi Alluvial Plain commonly referred to as the Delta. And we're going to talk to some farmers, were going to talk to some scientists and we're going to take a little bit of a tour of the Delta.

Richard, what have you been working on as far as the NAWQA program?

Richard Rebich:

Well, for the last couple of years I helped out with SPARROW modeling that the NAWQA program is doing. NAWQA group has wanted to do SPARROW models for various regions of the country, and the team that I worked with helped develop a SPARROW model for total nitrogen and total phosphorous in the south central United States. That study area goes from Arkansas all the way over to Colorado inclusive of Texas, Louisiana, parts of the Mississippi.

Richard Coupe:

What does the SPARROW model do?

Richard Rebich:

SPARROW model is kind of hybrid dynamic model and statistical model and it relates water-quality information that we collect in the field to landscape characteristics, sources of a particular pollutant, and it also relates it to those things that deliver those pollutants to the receiving stream. So we calibrate the model with multiple sites of whatever pollutant we're looking at or constituent that we're looking at in this case total nitrogen and total phosphorous. And then we relate that to sources of those particular constituents-- things like atmospheric deposition, point sources, runoff, other land use characteristics like fertilizer, manure…

And then how are those things transported to the stream, so variables that transport rainfall and runoff and soil characteristics like soil permeability those things contribute to the model. The model also includes decay rates and how these things what kind of losses you might have of these particular constituents before they hit the receiving stream or some target area that you're looking at.

Richard Coupe:

Why is this important to do?

Richard Rebich:

Well, originally the NWQA program put together a National model and that particular national model used sites from our old – well from our NASQAN program some of which are no longer in use. And there are about I'd say 450 calibration sites across the nation for the National SPARROW Model, and so they wanted to again regionalize some of this and look at smaller study areas and use not only USGS data and not only NASQAN data but also State databases and other databases that we could bring into the model. So like I said the National model had somewhere around 450 sites, and the models that we developed for just our small part of the United States had about the same number of sites.

So they wanted to expand those, and so these regional models were developed for about four or five different regions; across the country our Southeast, Northeast, Upper Mississippi River Basin, Missouri, and the Northwest.

Richard Coupe:

So what would be the most important results or most significant results that you found from this study?

Richard Rebich:

Well, from this study as you can imagine if we stretch from West Texas and Colorado over to the lower Mississippi valley, you're looking at an area from very arid to very humid wet conditions. So if you were to draw a line right down the middle of my study area, the right side – the eastern side of the study area would have most of your concentrations of cities. It would also have most of the agriculture and most of the sources if you're looking at it. As far as delivery terms and things that deliver those sources to the streams, the eastern side of our study area has the highest rainfall like I just said arid to humid.

So really the results follow that pattern, so the higher loads of nitrogen and phosphorous we saw in the eastern part and also along the coastal areas which was relatively expected. The one thing that I thought was really interesting was how much of the nitrogen load was contributed by atmospheric deposition it was greater than 40 percent. So with the other sources of nitrogen and phosphorous the higher sources came from the agricultural industry from fertilizer and manure inputs.

Richard Coupe:

Does this relate to the Gulf hypoxia zone at all?

Richard Rebich:

Yes, it would have a pretty good affect there. The hypoxia zone you know recent studies are pointing toward nutrients as the reasons. So where in the southern part of the United States are areas that contribute to the hypoxia zone, and we're able to see this as we map the loads for our particular study area. So this has implications of if you want to do something about the hypoxia zone if we think that it's related to the nutrients that hit there, then where do you start as far as trying to mitigate that? That's one of the strengths of SPARROW.

The mapping products that are produced will show you those hot areas or whatever where you can if another agency were to invest money into best management practices or some other source or some other way to mitigate where is the best bang for the buck in the study area. The other thing that we did was there's so much emphasis on the hypoxia zone that in the intercontinental shelf of the Gulf of Mexico that's been well documented related to the Mississippi River Basin. But there's really not a whole lot on smaller estuaries where hypoxia also exists.

So that's one of the things we wanted to provide the stakeholders for this study area is isolated maps of the loadings of total nitrogen and total phosphorous for the smaller watersheds, the smaller estuarine type water sheds along this particular study area. So that was the other thing that we did.

Richard Coupe:

Okay. Thanks.

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Duration: minutes