5.1 Conceptualization and characterization of a groundwater system is fundamental to any qualitative or quantitative analysis. This conceptualization begins with simple abstractions in the investigator's mind, emphasizing the major components of the studied system, that can be rendered in qualitative terms or simple illustrations. The extent of further development of the representation of the system depends on the character of the groundwater problem and the project objective. The abstract concept may suffice, or it may be further defined and quantified through use of analytical models of increasing complexity, and, in some cases, numerical models may be employed. If numerical models are used, the level of detail and sophistication of features represented in the model is likely to increase as the project develops. Evolution of conceptualization of a groundwater flow system should be terminated when the results of the related analyses are sufficient for the problem being addressed.

5.2 This guide may be used in the following:

5.2.1 Evaluating natural variations in groundwater flow systems.

5.2.2 Evaluating anthropogenic stresses on groundwater flow systems, such as pumping for water supply, irrigation, induced infiltration, or well injection.

5.2.3 Evaluating presence and velocity of groundwater contaminants.

5.2.4 Designing and selecting mathematical models to simulate groundwater systems; and completing model schematization and attribution based on the problem defined, characterized groundwater flow system, and model(s) selected.

5.2.5 Designing groundwater remediation systems.

5.3 This guide is a flexible description of specific techniques and investigation requirements; methods defined by other ASTM Standards or non-ASTM techniques may be appropriate in some circumstances and, after due consideration, some of the techniques herein may be omitted, altered, or enhanced.

5.3.1 A comprehensive list of items to be considered conceptualization and characterization are included in the main headings (Sections 6 through 13) and first subheadings (for example, 7.1 and 8.1).

5.3.2 In karst and fractured rock hydrogeologic settings, this guide should be used in conjunction with Guide D5717.

5.4 The methods and amount of effort required for conceptualization, characterization, and quantification of groundwater systems for modeling or other applications will vary with site conditions, objectives of investigation, and investigator experience. This guide does not replace proper academic training and experience in hydrogeologic principles, or in groundwater system analysis and quantification. This guide does not set mandatory guidelines and does not constitute a list of necessary steps or procedures for all investigations.

5.5 This guide may be used for project planning and data collection, but does not provide specific aspects for field characterization techniques. Refer to Table X1.1 in Guide D5730, Practice D5254/D5254M, and Refs (3, 4, 5, and 6) for further guidance regarding field characterization techniques.

5.6 This guide may be used to generate the necessary information as part of the process for model selection, design, and as input to model schematization, including the simplification of hydrologic systems and the representation of hydrogeologic parameters in models. Refer to Ref (7) for further guidance.

1.1 This guide covers an integrated, stepwise method for the qualitative conceptualization and quantitative characterization of groundwater flow systems, including the unsaturated zone, for natural or human-induced behavior or changes.

1.2 This guide may be used at any scale of investigation, including site-specific, subregional, and regional applications.

1.3 This guide describes an iterative process for developing multiple working hypotheses for characterizing groundwater flow systems. This process aims at reducing uncertainty with respect to conceptual models, observation, interpretation, and analysis in terms of hypothesis and refinement of the most likely conceptual model of the groundwater flow system. The process is also aimed at reducing the range of realistic values for parameters identified during the characterization process. This guide does not address the quantitative uncertainty associated with specific methods of hydrogeologic and groundwater system characterization and quantification, for example, the effects of well construction on water-level measurement.

1.4 This guide addresses the general procedure, types of data needed, and references that enable the investigator to complete the process of analysis and interpretation of each data type with respect to geohydrologic processes and hydrogeologic framework. This guide recommends the groups of data and analysis to be used during each step of the conceptualization process.

1.5 This guide does not address the specific methods for characterizing hydrogeologic and groundwater system properties.

1.6 This guide does not address model selection, design, or attribution for use in the process of groundwater flow system characterization and quantification. This guide does not address the process of model schematization, including the simplification of hydrologic systems and the representation of hydrogeologic parameters in models.

1.7 This guide does not address special considerations required for characterization of karst and fractured rock terrain. In such hydrogeologic settings, refer to Quinlan (1)2 and Guide D5717 for additional guidance.

1.8 This guide does not address special considerations regarding the source, fate, and movement of chemicals in the subsurface.

1.9 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.10 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard 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 document 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.

1.11 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.