ASTM D6036-96(2008)

Each year many thousands of water samples are collected and the chemical components are determined from natural and human-influenced groundwater sources.

The objective interpretation of the origin, composition, and interrelationships of water can be simplified by displaying the distribution of the constituents and related parameters on areal maps (1,2).

The origin of the chemical composition of the water may be postulated by the amount and the distribution of the constituents as shown on the maps.

The chemical composition of the water can be scrutinized for distinct characteristics and anomalies by use of the maps.

The interrelationships of the water chemistry from various sampling locations can be visualized on the maps.

This guide presents various mapping methods for showing distribution of chemical constituents using areal and time-related trends; maximum, minimum, or mean values; and relationships between chemical and associated parameters.

Exercise caution when interpreting the distribution of chemical constituents on two-dimensional (X and Y) maps as liquids of different densities tend to stratify in the third dimension (Z).

Note 2—Water (or other liquid) with a relatively low concentration of dissolved solids (or of a low relative density) normally will float on top of water with high dissolved solids or a liquid of higher density (3-7). A naturally occurring example is an island surrounded and underlain by sea water where rain water falling on the island forms a fresh water lens above the underlying sea water. Where the presence of liquids of different densities are evident in a mapped area, cross sections of the aquifer assist in showing the vertical (Z) distribution of the chemical constituents or a pattern can be used on the map to delineate the extent of this water.

Note 3—Immiscible liquid contaminants, such as petroleum products, with a relative density less than that of the water will float on top of the water. Liquids that are more dense than water will flow to the bottom of the aquifer. Miscible liquids, such as sea water, mix with the fresher water creating a zone of dispersion at the interface of the two liquids.

Aquifers in fractured rock or karst areas may result in noncontinuum conditions for the chemical parameters in the water (Guide D5717). This guide assumes the aquifer usually consists of an equivalent porous media.

This is not a guide for the selection of a map technique for a distinct purpose. That choice is program or project specific.

Note 4—For many hydrochemical research problems involving the scientific interpretation of groundwater, the areal map is only one segment of several methods needed to interpret the data.

1.1 This guide offers a series of options but does not specify a course of action. It should not be used as the sole criterion or basis of comparison and does not replace or relieve professional judgment.

1.2 This guide covers methods that display, as mapped information, the chemical constituents of groundwater samples. Details required by the investigator to use fully the methods are found in the listed references.

1.2.1 The use of maps to display water-quality data are a common technique to assist in the interpretation of the chemistry of water in aquifers, as the areally distributed values can be easily related to the physical locality by the investigator.

1.2.2 The distribution in an aquifer of chemical constituents from two water sources or of liquids of different densities may be difficult to illustrate explicitly on a two-dimensional map because of stratification in the third dimension. Also, the addition of a vertical cross section may be required (see 4.4).

1.3 Many graphic techniques have been developed by investigators to assist in summarizing and interpreting related data sets. This guide is the fourth document to inform the hydrologists and geochemists about traditional methods for displaying groundwater chemical data.

1.3.1 The initial guide (Guide D5738) described the category of water-analysis diagrams that use pattern and pictorial methods as a basis for displaying each of the individual chemical components determined from the analysis of a single sample of natural groundwater.

1.3.2 The second guide (Guide D5754) described the category of water-analysis diagrams that use two-dimensional trilinear graphs to display, on a single diagram, the common chemical components from two or more analyses of natural groundwater.

1.3.3 The third guide (Guide D5877) presented methods that graphically display chemical analyses of multiple groundwater samples, discrete values, as well as those reduced to comprehensive summaries or parameters.

1.4 Notations have been incorporated within the illustrations of this guide to assist the user in understanding how the maps are constructed. These notations would not be required on a map designed for inclusion in a project document.

Note 1—Use of trade names in this guide is for identification purposes only and does not constitute endorsement by ASTM.

1.5 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.