# TOUGH Development History

The TOUGH software was developed and continuing improved at Lawrence Berkeley National Lab by dozens of scientists. The first release of TOUGH was in 1987 (Pruess, 1987) for simulations of nonisothermal flow of water and air in aqueous and gaseous phase, which is based on the research software MULCOM (Pruess, 1983). In 1991, the second generation of TOUGH was released and named as TOUGH2 by including simulation of subsurface flow of different non-condense gases. The TOUGH2 was further improved in process modeling capabilities and formed the TOUGH2 V2 (Pruess et al., 1999). After the release of TOUGH2 V2, many process modeling modules had been developed, such as ECO2N (Pruess, 2005 ), TMVOC([Pruess and Battistelli, 2002)](https://tough.lbl.gov/assets/docs/TMVOC_Users_Guide.pdf), and EOS7C(Oldenburg et al. , 2004)). In 2008, the massively parallel version of TOUGH2, TOUGH2-MP, was released (Zhang et al., 2008). In 2018, The third generation of TOUGH, named TOUGH3 (J[ung et al., 2018](https://drive.google.com/file/d/1UpXlAD7k312X2mthpsCp7OJgOwFvXC8g/view)), was published. TOUGH3 incorporated more process modeling modules and consolidated the series and parallel version of the simulator. In 2008, Moridis et al. developed TOUGH+, which re-wrote TOUGH2 in modern Fortran and expanded it for the simulations of hydrate-bearing geologic media and mixed gases. In the past three decades, a series of satellite software of TOUGH has been developed, such as TOUGHREACT, ITOUGH, TOUGH-FLAC, and some specific-purpose EOS Modules (Figure 1).

<figure><img src="/files/wCCSZa7p4mPEdegJQaGV" alt=""><figcaption><p>Figure 1. Development history of TOUGH and its satellites</p></figcaption></figure>


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://lbl-2.gitbook.io/tough4-user-manual/introduction/tough-development-history.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.