Significance and Use 4.1 Groundwater modeling has become an important methodology in support of the planning and decision-making processes involved in groundwater management. Groundwater models provide an analytical framework for obtaining an understanding of the mechanisms and controls of groundwater systems and the processes that influence their quality, especially those caused by human intervention in such systems. Increasingly, models are an integral part of water resources assessment, protection, and restoration studies, and provide needed and cost-effective support for planning and screening of alternative policies, regulations, and engineering designs affecting groundwater.4 4.2 Many different groundwater modeling codes are available, each with their own capabilities, operational characteristics and limitations. Furthermore, each groundwater project has its own requirements with respect to modeling. Therefore, it is important that the most appropriate code is selected for a particular project. This is even more important for projects that require extensive modeling, or where costly decisions are based, in part, on the outcome of modeling-based analysis. 4.3 Systematic and comprehensive description of project requirements and code features provides the necessary basis for efficient selection of a groundwater modeling code. This standard guide is intended to encourage comprehensive and consistent description of code capabilities and code requirements in the code selection process, as well as thorough documentation of the code selection process.Scope 1.1 This guide covers a systematic approach to the determination of the requirements for and the selection of computer codes used in a groundwater modeling project. Due to the complex nature of fluid flow and biotic and chemical transport in the subsurface, many different groundwater modeling codes exist, each having specific capabilities and limitations. Furthermore, a wide variety of situations may be encountered in projects where groundwater models are used. Determining the most appropriate code for a particular application requires a thorough analysis of the problem at hand and the required and available resources, as well as detailed description of the functionality of candidate codes. 1.2 The code selection process described in this guide consists of systematic analysis of project requirements and careful evaluation of the match between project needs and the capabilities of candidate codes. Insufficiently documented capabilities of candidate codes may require additional analysis of code functionality as part of the code selection process. Fig. 1 is provided to assist with the determination of project needs in terms of code capabilities, and, if necessary, to determine code capabilities. 1.3 This guide is one of a series of guides on groundwater modeling codes and their applications, such as Guides D5447, D5490, D5609, D5610, D5611, D5718, and D6025. 1.4 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This guide cannot replace education or experience and should be used in conjunction with professional judgement. Not all aspects of this guide may be applicable in all circumstances. This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this guide be applied without consideration of a project’s many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
