NDR Exports vs. Loads

After running the NDR model I get total N export and total P export along with total loads for both nutrients. When comparing to observed data (annual loads), which should I be using? I would assume total loads, but my total export numbers are WAY closer to the observed data than my total load numbers.

Hi @audiae -

N/P export represent the amount of nutrient that makes it to the stream. If your observed data is from stream gauges, then you should be using export to compare against the observed data.

Loading represents the amount of nutrient that leaves a pixel on the landscape. This would mainly be comparable if you have observed measurements at, say, a plot level.

~ Stacie

Thank you! That helps a lot!

Sorry to bother you but I really want to know where can you get observed data(annual loads)from or can I use the observed data( water quality: the concentration of total N\P in water) to calidate?


I used USGS water quality monitoring data collected from here: https://maps.waterdata.usgs.gov/mapper/index.html

I also used the USGS SPARROW model to get an idea for numbers in my watershed. You can find it here, but it only reflects data from 2002 and is modeled data. I would read the documentation before using it as calibration data.

thanks very much


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