How to extract source contributions (surface runoff, soil, geology) to stream water in ATS

Xueyuan Kang

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Jul 23, 2025, 1:31:50 PMJul 23

to Amanzi-ATS Users

Hello all,

I’m currently working on quantifying the contributions of different sources to stream water (e.g., soil layers, geological layers, and surface runoff) at specific locations—such as a point in the upstream and another in the downstream.

(1) surface runoff:

I’m trying to extract it at the pixel scale. I understand that surface-water_flux would be the appropriate variable, but it’s defined on faces rather than cells, and it doesn’t appear in the ats_vis_data.h5 output by default. I also looked at surface-darcy_velocity, but it only shows non-zero values along the river channels, while hillslope values remain zero, making it unsuitable for capturing surface runoff elsewhere.

Is there a recommended way to extract surface runoff at the pixel scale in ATS? Would it be best to define a small region (e.g., a boundary enclosing the pixel) and use the observation block to compute it? For example:

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(2) Subsurface fluxes (soil and geology layers):

To compute the flux from soil and geologic layers into the stream, is it reasonable to use the Vy component (assuming the stream is aligned along the x-direction) from cells adjacent to the stream channel? My current idea is to calculate fluxes as Vy × area for each cell at various depths, and then sum contributions from cells corresponding to the soil or geological layers.

Does this approach make sense, or is there a more appropriate way to separate and quantify contributions from each subsurface layer to the stream?

Any suggestions, clarifications, or best practices would be greatly appreciated!

Best regards,

Xueyuan

Coon, Ethan

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Jul 23, 2025, 4:13:48 PMJul 23

to Xueyuan Kang, Amanzi-ATS Users

So if the surface water velocity is zero, then the lateral fluxes to and from that cell are zero (and correspondingly the ponded depth is either zero or water isn’t flowing because the water surface is flat). You can check this by doing a surface-only run, or setting a very low permeability to force surface water.

I think what you want is the surface-water_velocity (I don’t think it’s called surface-darcy_velocity anymore, at least not in master).

Ethan

From: ats-...@googlegroups.com <ats-...@googlegroups.com> on behalf of Xueyuan Kang <xueyuan...@gmail.com>
Date: Wednesday, July 23, 2025 at 11:32 AM
To: Amanzi-ATS Users <ats-...@googlegroups.com>
Subject: [EXTERNAL] How to extract source contributions (surface runoff, soil, geology) to stream water in ATS

Hello all, I’m currently working on quantifying the contributions of different sources to stream water (e. g. , soil layers, geological layers, and surface runoff) at specific locations—such as a point in the upstream and another in the downstream.

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Xueyuan Kang

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Jul 26, 2025, 3:27:03 PMJul 26

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Hi Ethan,

Thanks for your quick reply. Yes, it is surface-velocity in ATS-1.5. I will try to calculate the surface runoff by surface-velocity*area.

Thanks.

Xueyuan

Coon, Ethan

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Jul 26, 2025, 3:29:28 PMJul 26

to Xueyuan Kang, Amanzi-ATS Users

Velocity is m/s. I’m not sure what your goal in multiplying by area is. What area do you mean? A flux is only defined across an area, which on the surface should actually be ponded depth times the length of the line across which you are computing the flux.

Ethan

From: ats-...@googlegroups.com <ats-...@googlegroups.com> on behalf of Xueyuan Kang <xueyuan...@gmail.com>
Date: Saturday, July 26, 2025 at 1:27 

PM
To: Amanzi-ATS Users <ats-...@googlegroups.com>
Subject: Re: [EXTERNAL] How to extract source contributions (surface runoff, soil, geology) to stream water in ATS

Hi Ethan, Thanks for your quick reply. Yes, it is surface-velocity in ATS-1. 5. I will try to calculate the surface runoff by surface-velocity*area. Thanks. Xueyuan On Wednesday, July 23, 2025 at 2: 13: 48 PM UTC-6 Coon, Ethan wrote: So if the

To view this discussion visit https://groups.google.com/d/msgid/ats-users/28fe13e0-693a-4c8c-84e0-22df92e13aacn%40googlegroups.com.

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