ATS Demo Problems

The best way to learn how to use ATS is by looking at our suite of demonstration problems. This is a suite of problems that look to provide many simple, and some complex, examples of how to link together the various physics capabilities in ATS.

In all, for every process in ATS, we try to provide at least one example, and preferably two – one that is simple and shows how the process works, and one that is complex and shows how it links to other processes in a real problem. In addition to input files for these examples, we strive to include a Jupyter notebook which explains all needed inputs and outputs of that example, and shows some plots that demonstrate how the process works. This is somewhat aspirational at the moment – our demos do not cover the entire suite of processes – but new demos are always welcome contributions.

The problems are organized by type of capability, and include multiple examples. For instance, the ecohydrology notebook includes examples of evaporation and transpiration through a broad range of complexity of approaches, from prescribed values to Priestley-Taylor evaporation to fully biogeophysical models.

Note that ats-demos is its own repo. This repo can be checked out (either standalone or as a submodule of ATS), and the demos can be run, modified, etc. Installation notes for the demos are included in that repository in its README.

Richards Equation: Steady state

ats_demos/01_richards_steadystate/richards_steadystate.ipynb

This shows examples of solving Richards equation to steadystate. Typically this is used to establish a water column that satisfies hydrostatic balance.

Richards Equation: Transient

ats_demos/02_richards/richards.ipynb

Transient problems show a variety of variably saturated cases, and demonstrate seepage faces and other common boundary conditions for the flow of water in a porous media.

Surface Water

ats_demos/03_surface_water/surface_water.ipynb

Overland flow is solved through a diffusion wave equation. This demonstrates that as a standalone capability, solving surface water problems to demonstrate common usages of boundary conditions and forcing.

Integrated Hydrology

ats_demos/04_integrated_hydro/integrated_hydro.ipynb

Integrated hydrology brings the previous two examples together, solving both surface and subsurface flow of water.

Ecohydrology

ats_demos/05_ecohydrology/ecohydrology.ipynb

Ecohydrogy brings in the effects of other ecological processes, here loosely used to include all surface processes like evaporation, transpiration, and canopy processes like interception and storage, and even simplified biogeochemistry processes for a full carbon cycle.

Arctic Hydrology

ats_demos/06_arctic_hydrology/arctic_hydrology.ipynb

ATS was originally developed as an Arctic hydrology simulator. It includes state-of-the art constitutive models and numerical methods for solving coupled freeze-thaw processes in Arctic environments.

Reactive Transport

<ats_demos/07_reactive_transport/reactive_transport.ipynb> (Work in progress)

ATS’s sister code Amanzi was designed for solving problems of reactive transport. Interoperability of ATS and Amanzi allows ATS to leverage this work to solve problems of nonreactive and reactive transport in both the surface and subsurface, and even in frozen environments. (See below for ATS reactive transport demos when used with integrated hydrology)

Integrated hydrology and Reactive Transport

<ats_demos/13_integrated_hydro_reactive_transport/integrated_hydro_reactive_transport.ipynb>

ATS is unique in the its ability to simulate reactive transport in integrated hydrology problems. In other words, it is capable of simulating muticomponent reactive transport in both surface and subsurface compartments using a novel coupling approach, and levering powerful, external geochemical engines Molins et al (2022) WRR