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NDR model related

Hello, I would like to ask you about the results of the NDR model.
I'm wondering where the blank (null value) appears in the resulting map of P retention.(see attachment below)

- (The retention map is made by equation (1-ndr) * load_P. )

When working with DEM in the input data construction stage, I wonder if it is because the watershed is not created, or because it is the stream where the river meets.
I would appreciate it if you could explain why or explain a null value.

Yoon Sun Park.
939 x 843 - 188K


  • swolnyswolny Member, NatCap Staff
    Hello @ysunparc -

    You are correct that there are null values where the model creates streams - you can see this by comparing the "stream.tif" output from the model with your result map. This is because NDR does not do any processing within stream channels. Nutrient is moved down slope until it reaches a stream, then the model stops calculating. This is one of its simplifications, as in-stream processes are more complicated to model. 

    ~ Stacie
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