Question about output units (mm/year, km3/year)

[rubcalvo]

Dear all, I've been working with xanthos for the past month and I'm having trouble to understand the conversion between mm/year to km3/year in the output files. Running the example file (https://zenodo.org/record/2578287) both in km3peryear and mmperyear outputs options gives differentes results. For example: for Arctic Ocean Islands basin, in the year 1971, the run with km3 gives a runoff of 200.778857, and the run with mm gives 224395.703522.

If I understand correctly, 1 mm of water corresponds to 1 kg of water (in volume terms: 1mm x 1m x 1m), hence to convert it to km3 I would have to divide the mm quantity by 1e12. As it don't result in the same number, I divided the km3 column with the mm column in my dataset to see what is the ratio between them.

This gives a ratio between 0.001 and 0.003, it varies between basins and is correlated with the basin id. Hence, I thought that the conversion happens taking into account the area of the basin, but then mmperyear should not correspond to the total but the mean or something like that. However, the ratio varies slightly between years also, (for example: for Arctic Ocean Islands between 1971-2001 it varies between 0.001006 and 0.001143).

Would appreciate so much if someone can clarify this.
Thanks,