Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
65
Graphical Techniques of Presentation of Hydro-Chemical Data
Mohammed, Dauda
*
Ramat Polytechnic Maiduguri, Department of Civil Engineering Technology
P.M.B. 1070 Maiduguri, Borno State, Nigeria.
Email: mohammedawud@gmail.com
Garba Abba, Habib
Ramat Polytechnic Maiduguri, Department of Building Technology
P.M.B. 1070 Maiduguri, Borno State, Nigeria.
Email: garbu73@gmail.com
Abstract
Water is vital to man’s existence and early human civilizations centered on springs and streams for their day to
day activities with water which is vital for survival. Throughout history, people around the world have used
groundwater as a source of drinking water and even today, more than half of the world’s population depends on
groundwater for survival. Pure water does not exist in nature due to various interactions between the geologic
Formation as well as atmospheric gases such as Carbon dioxide and Oxygen, hence the need for chemical
analysis of water. Determination of concentration of various ions is one major form of chemical analysis.
Because of the number of ions involved, it is usually more convenient to present the results in graphical forms
for easy understanding of the water samples analyzed. There are several methods of graphical presentation which
includes Bar Chart, Pie Chart, Stiff Diagram, Schoeller Diagram, Piper Diagram and Scattered Plots. For
instance Bar chart, Pie Chart, Stiff Diagram are good for small numbers of chemical data, whereas the Schoeller,
Piper Diagrams and Scattered Plots are suitable for presentation of results for large numbers of chemical data.
Keywords: Groundwater, Hydrochemistry, Graphical, Molality and Water type
INTRODUCTION
Natural waters are never pure; they always contain at least small amounts of dissolved gases and solids, because
of the interactions with both atmosphere as well as the geological formations. For most of it's used the chemical
properties and available quantity. Water constitutes about two third of the earth volume, while the rest is covered
by land surface. Water occurs in three places in the earth. It occurs in the atmosphere in form of condense
vapors, in lithosphere that is pore spaces in both inter/intra granular spaces in sedimentary rocks and fractures
and veins in both igneous and metamorphic rocks. Whereas in hydrosphere in oceans, streams, rivers and lakes.
An important task in groundwater investigation is the compilation and presentation of chemical data in a
convenient manner for visual inspection, for these purpose several commonly used graphical methods are
available. Among these is the bar chart (Freeze and Cherry 1979). Water in these various environments or area is
characterized by unique concentration of organic, inorganic and bacteriology constituent tend to define the
usability of the water. But it is worth noting that acceptable concentration limit is control by the purpose for
which the water is used. Since there is no pure water in nature, there is need for chemical and biochemical
constituent determination. Its suitability for utilization in the industry, it is therefore very necessary to undergo
geochemical studies in water. Complete chemical analyses of a water sample include the determination of
concentration of the inorganic constituent present, radiological and organic parameters are normally of concern
only where human being influence the pollution that affect the quality.
Dissolved salts in water of normal salinity occur as dissociated ions plus other minor constituents are
present and reported in elemental form. Chemical impurities in water can cause many health hazards. The
analysis also include physical parameter such as pH and electrical conductivity, depending on the purpose for
water quality investigation, partial analysis of only particular constituent will at time suffice. In a chemical
analysis of water, concentration of different ions are expressed by weight or by chemical equivalence, some
properties of the water properties evaluated in a physical analysis include colour, odour, temperature, taste and
turbidity.
HYDROCHEMISTRY
Hydrochemical composition of water is as important as any other properties of water. The chemical components
of water did not only indicate the quality of water, but also help to infer the geology of the area. Hydrochemistry
is concerned with the chemical analysis of water, which involves determination of the concentration of the in-
organic constituents present. In describing units and expressions for water quality, standard exist that are used to
interpret the quality for suitability for a particular purpose. Concentrations of different ions are expressed in by
chemical equivalent or weight.
brought to you by COREView metadata, citation and similar papers at core.ac.uk
provided by International Institute for Science, Technology and Education (IISTE): E-Journals
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
66
UNITS OF REPORTING RESULTS
The results of chemical analyses are always presented or reported in concentration units. Various types of
concentration units are in used.
CONCENTRATION BY WEIGHT
The concentrations of the common ions found in groundwater are reported by weight per volume units of
milligrams per litre (mg/l).
CHEMICAL EQUIVALENCE
Positively charged cations and negatively charged anions combine and dissociate in definite weight ratio. By
expressing ion concentrations in equivalent weights, these ratios are readily determined because one equivalent
weight of a cation will exactly combine with one equivalent weight of an anion. The combining weight of an ion
is equal to its formula weight divided by its charge.
MAJOR CATIONS AND ANIONS WITH THEIR CONVERTION FACTORS FOR CHEMICAL
EQUIVALENCE (After Todd. 2004)
CATIONS ION
CONVERSION FACTORS
Calcium Ca
2+
0.0499
Magnesium Mg
2+
0.08226
Sodium Na
+
0.0435
Potassium K
+
0.02557
ANIONS ION CONVERSION FACTORS
Bicarbonate HC0
3
-
0.01639
Sulphate SO
4
2
-
0.02082
Chloride Cl
-
0.02821
MOLARITY
Is defined as the number of solutes in 1m
3
of a solution. The unit for molarity is designated as mol/m
3
.
MOLALITY
Is also defined as the number of moles of solutes dissolved in a kilogram mass of a solution. The unit is mol/kg.
Therefore one mole of a compound is the equivalent of one molecular weight.
MASS CONCENTRATION
Is also defined as mass of solute dissolve in a specified unit volume of solution. The unit is also in kg/m
3
. Gram
per litre (g/l) is a permitted unit, but the most common mass concentration unit reported in the groundwater
literature is milligrams per litre i.e. (mg/l).
There are many other non concentration units used in groundwater literature are parts per million
(ppm) equivalent per litre (epl), equivalent per million (epm) are all very important unit of reporting because in
chemical reactions equivalent of anions. Therefore if cations and anions are expressed in (meq/l) it is possible to
check the accuracy of the analysis, by comparing the equality of the cations and anions. Because natural water
contains a variety of ionic and undissociated species, conductance cannot be simply related to total dissolved
solids, conductance is easily measured and gives results that are convenient as a general indication of dissolved
solid. Results of analyses of chemical quality of water samples are most conveniently presented in graphical
form. The purposes are stated below:
Display purpose
Comparing analyses
Emphasizing similarities and differences
These graphical representation also aid in detecting the mixing of water difference composition and
identifying chemical process occurring as water move. A great number of naturally occurring minerals poses the
ability of exchanging one ion for another, such processes usually involve cations. The cations which are most
common are calcium, magnesium and sodium and the exchange actually takes place when ions absorbed in
mineral grain surface are not the same as those in the water. The process of exchange terminates when
equilibrium is established between the cations of the matrix and the cation in the water. Obviously, such
phenomenon has a great bearing upon the chemical composition of water for instance zeolites. These constitutes
a group of hydrous, aluminium silicate possessing calcium and sodium as important component when water
traverses such minerals, sodium ions exchange with calcium and magnesium ions in the water and thus reduce its
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
67
hardness, this process is therefore term the evolution of ions.
HYPOTHETICAL RESULTS USED IN THE GRAPHICAL PRESENTATIONS
Cations Anions
Sample A Ca
2+
Mg
2+
Na
+
K
+
Hco
3
-
So
4
2
-
Cl
-
Mg/l 36.7 14.6 40.1 8.2 Total
22.7 29.5 7.2 Total
Meq/l 1.83 1.2 1.74 0.21 4.98
0.37 0.61 0.2 1.18
Percentage 36.7 24.1 34.9 4.2 100
31.4 51.7 16.9 100
Degree 66.1 43.4 62.8 7.6 180
56.5 93 30.4 180
Cations
Anions
Sample B Ca
2+
Mg
2+
Na
+
K
+
Hco
3
-
So
4
2
-
Cl
-
Mg/l 14.4 3.9 20.5 7.1 Total
101 9.9 3.4 Total
Meq/l 0.72 0.32 0.89 0.18 2.11
1.66 0.21 0.1 1.97
Percentage 34.1 15.2 42.2 8.5 100
84.3 10.7 5.1 100
Degree 61.4 27.4 76 15.3 180
151.7 19.3 9.2 180
Cations
Anions
Sample C Ca
2+
Mg
2+
Na
+
K
+
Hco
3
-
So
4
2
-
Cl
-
Mg/l 26.6 6.2 4.5 8.2 Total
44.6 6.6 3.1 Total
Meq/l 1.33 0.51 0.21 0.21 2.26
0.73 0.14 0.09 0.96
Percentage 58.8 22.6 9.3 9.3 100
76 14.6 9.4 100
Degree 105.8 40.7 16.7 16.7 180
136.8 26.3 16.9 180
Cations
Anions
Sample D Ca
2+
Mg
2+
Na
+
K
+
Hco
3
-
So
4
2
-
Cl
-
Mg/l 27.3 4.5 16.6 12.9 Total
81 35.2 7.1 Total
Meq/l 1.36 0.37 0.72 0.33 2.78
1.33 0.73 0.2 2.26
Percentage 48.9 13.3 25.9 11.9 100
58.8 32.3 8.8 100
Degree 88 23.9 46.6 21.4 180
105.8 58.1 15.8 180
GRAPHICAL METHODS
Constituents in solution in water may be viewed as a chemical system with cations and anions in equilibrium
with each other. In discussing graphical methods of presentation for this system, Piper (1944) noted the
abundance of the cations calcium, magnesium, sodium and potassium and anions bicarbonate, sulphate and
chloride. He proposed that ionic solutions of water be treated as though they contained three cations groups and
three anion groups. The less abundant cation and anion constituents are summed with the major constituents in
accordance with common physical properties and are therefore accounted for in the plotting method. To convert
the result of chemical analysis into a suitable form for graphical interpretation, all result in milligram per liter is
converted to milli equivalent per liter by multiplying it with a conversion factor. For a complete analysis the total
equivalent weight of cations and anions in solution must be equal or same, to the extent that natural water can be
treated in terms of 3 cation constituents and 3 anion constituents, the chemical character can be shown
graphically by a single point on a conventional Piper diagram. There are several varieties of graphical techniques
that have been developed for the presentation of chemical components of water. The major chemical constituents
are usually used for the presentation. An important task of water investigation is the compilation and
presentation of chemical data in a convenient manner for visual inspection. Graphs are used in comparing the
similarities and differences in the concentration of the chemical constituents in each water sample analyzed.
Graphs are also used in detecting mixing of water of different composition and identifying chemical processes
occurring as water passed through the aquifer system. For this purpose, a variety of data presentation techniques
have been developed for showing the major chemical constituents over the year and these include:
Bar Charts
Pie Charts
Stiff Diagrams
Scattered Plots
Schoeller Diagrams
Piper Diagram
BAR CHARTS
The bars are plotted with concentration values in milli equivalent per liter. It is widely used in portraying
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
68
chemical quality. Each analysis appears as a vertical bar having a height proportional to the total concentration
of anions or cation. These graphs show the relative and total concentration of dissolved constituents present. Bar
charts show the similarities or difference between water from their concentration ranges and it also show clearly
the chemical constituent of total cations are plotted to the left of vertical bar and anions to the right. These
segments are divided horizontally to show the concentration of major ions or groups of closely related ions and
identified by distinctive shading pattern.
ADVANTAGES OF BAR CHARTS
It gives an idea of the overall concentration of cations and anions.
Visually strong.
Can easily compare two or three data set.
DISADVANTAGES OF BAR DIAGRAM
It is not suitable for large water samples.
It does not give clear water type characteristics.
Use only with discrete data.
PIE CHARTS
Represent the total concentrations of major cations and anions of water sample by means of circle. The segments
of the circle are indicative of the percentage composition, i n degree. The diagrams of this type are probably
most useful for indicating the composition of water on a geologic section or column.
ADVANTAGES OF PIE CHARTS
Visually appealing.
Shows percent of total for each category.
It provides quick visual comparison of individual chemical analyses.
DISADVANTAGE OF PIE CHARTS
It is not suitable for large graphical presentation of analyses.
Hard to compare 2 data sets.
Use only with discrete data.
STIFF DIAGRAM
Stiff (1951) proposed another way of presenting chemical analysis data, in which he used four parallel axes and
one vertical axis for representing the chemical analysis. The procedure as proposed by Stiff (1951) is such that
four cation concentrations are plotted to the left of the vertical zero axis and four anions to the right, all value are
in milli equivalent per liter. The resulting point, when connected form an irregular polygonal pattern, waters of a
similar quality define a distinctive shape from other of different quality. Stiffs method may be useful in making
comparison of water, especially highly mineralized ones, is simple to use and can be varied to suit the water
being studied. !t is more applicable to groundwater data that are interrelated than to miscellaneous surface water
analyses. Stiff patterns are useful in making a rapid visual comparison between water from different sources. The
use of the lower horizontal bar with ion of carbonate is optional as in much water they are close to zero. The
larger the area of polygon shapes the greater the concentrations of the various ions.
ADVANTAGES OF STIFF DIAGRAMS
It is relatively simple to construct.
It gives a clear pattern for ions of the same water type.
It gives a direct picture of the water type by means of shapes.
DISADVANTAGES OF STIFF DIAGRAM
It is not convenient for large samples analysis.
It does not give the concentration of ions present in direct form.
SCATTERED PLOTS
The scattered plot enables us to see the relationship between the two variables at once. It can be used to
determine the relationship between two set of data. The measure of this relationship between any of these two
variables (variables mean things taking different values or forms) is called correlation. Therefore calculating
correlation coefficients is the calculation of the measure of relationship which gives the indication of the size or
magnitude of the relationship. When we plot the values or points on the rectangular coordinate axes (our usual
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
69
graph paper) indicating x and y axes, the resulting picture is the scattered plot.
ADVANTAGES OF SCATTERED PLOTS
Shows a trend in the data relationship.
Retains exact data values and sample size.
Shows minimum/maximum and outliers.
DISADVANTAGES OF SCATTERED PLOTS
Hard to visualize results in large data sets.
Flat trend line gives inconclusive results.
Data on both axes should be continuous.
SCHOELLER SEMILOGARITHMIC DIAGRAM
Schoeller (1962) proposed the use of semi logarithmic graph paper to plot the concentration of anions and
cations. The concentrations are plotted in milli equivalent per liter. That type of diagram allows us to make a
visual comparison of the composition of different water. They are plotted on six equally spaced logarithmic
scales in the arrangement. The points plotted are joined by straight line. This type of graph shows not only the
absolute value of each ion but also the concentration differences among various groundwater analyses. Because
of the logarithmic scale, a straight line joining the points A and B of two ions in a water sample is parallel to
another straight line joining the point A and B of the same ions in another water sample the ratio of the ions in
both analyses is equal.
ADVANTAGES OF SCHOELLER DIAGRAM
It is widely used for comparing water analyses.
It can be adapted to determine the degree of saturation in water.
It shows the concentration difference among various water analyses.
DISADVANTAGE OF SCHOELLER DIAGRAM
It does not show the water type directly.
Use only with continuous data.
PIPER DIAGRAM
This method was developed by Arthur M. Piper. (1944). Diagram reveals similarities and differences among
large number of groundwater samples because those with similar qualities will tend to plot together as groups.
The following are steps for plotting a Piper diagram.
1. Calculate the concentration of the analysed major ions (Na
+
, K
+
, Mg
2+,
Ca
2+
, Cl
-
, HCO
3
-
, CO
3
2-
, and
SO
4
2-
) in milli equivalent per liter.
2. Calculate the percentage milli equivalent of anions and cations respectively, combining Na
+
and K
+
, CO
3
2-
and HCO
3
-
.
3. Plot each value in the cations - anions triangle at the base of the central diamond shape field.
4. Extend the point by dotted lines into the central diamond field.
5. According to total dissolved solids concentration point of intersection of the extended dotted lines from
both cations and anions triangles might be enlarged or circled.
The total dissolved solids concentrations are often not important in the first stage of geochemical interpretation
and points are often sufficient and allow larger number of samples to be plotted. By the use of Piper diagram
chemical relationship among waters may be brought out in more definite terms than is possible with any other
plotting graphical procedure. Piper plotting is a very useful interpretative tool in groundwater chemistry.
ADVANTAGES OF PIPER DIAGRAM
It is most useful for representing and comparing water quality because it reveals the similarities and
difference among water samples.
It directly gives you the various water types.
It can handle results of many samples of water within the same graph.
DISAVANTAGES OF PIPER DIAGRAM
It is not good for a few data sets that’s make it hard to be compared.
WATER TYPES
From the chemical analysis and graphical techniques used in these paper presented, the following water types
were obtained;
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
70
SAMPLE A Ca-Na-Mg
SAMPLE B Na-Ca-HCO
3
SAMPLE C Ca-Mg-HCO
3
SAMPLE D Ca-Na-HCO
3
-SO
4
DISCUSSION OF RESULTS
The general dominance of calcium bicarbonate and sulphate in the water samples analysed is related to the rocks
minerals which released these ions into solution after their weathering. Feldspars and micas when K
+
, Mg
2+
, and
Ca
2+
are leached out leaving clay minerals such as Kaolinite, Elite, Montmorilonite etc. Most carbonate and
bicarbonate in groundwater are derived from the carbon dioxide in the atmosphere, soil and solution of carbonate
rocks. Sodium bicarbonate water can be concentrated by evaporation in the soils and desert basins. Despite a
relatively large amount of sulphur mostly in form of sulphate in water and sedimentary rocks, Sulphates are
derived from the solution of sulphate minerals in sedimentary rock particularly organic shale may also yield
large amount of sulphate through the oxidation of marcasite and pyrite. Considering both the Bar and Pie charts
(see sample d & a) in figure 4 and 5 in appendix. Ca
2+
is the most dominant cation followed by alkali of Na
+
+
K
+
and the least is the Mg
2+
.
While on the anions species, HCO
3
-
is the most dominant followed by SO
4
2-
and the least CI
-
ion which
is a strong acid. The plots of the chemical compound from water samples (a) and (b) seems to be scattered within
the diamond field showing a different characteristic, the other plotted sample (c) and (d) points together as a
group within the diamond field in the Piper diagram (see figure 9) in the appendix which indicates similar water
type of same characteristics. The plots from the schoeller diagram (see figure 10) in the appendix indicate no
particular trends in the water samples analyzed. The haphazard arrangement support different water types in
sample (a) and (b) and a closer look at both sample (c) and (d) seems to be closely related as indicated by the
Piper (1944) diagram. The Stiff diagram (see figure 11, 12, 13 & 14) in the appendix shows differences in shapes
of the water sample analyzed. These differences in shapes in form of hexagons in sample (a) and (b) shows
different water types, that is to say no mixing of water and the similarity of hexagonal shape in sample (c) and
(d) indicate water of similar characteristics. Therefore both the Bar, Pie and Stiff diagrams are all easier to
construct and provide quick visual comparison of individual chemical analyses and they are good in plotting
small number of water samples, for large number of chemical data analysis the Piper (1944) diagram is more
suitable.
SUMMARY AND CONCLUSION
This work shows the different techniques used in presenting hydrochemical data of water samples. These
techniques include the Bar charts, Pie charts, Scattered plots, Stiff diagrams, Schoeller semi logarithmic diagram
and the Piper diagram. The first four techniques are only suitable for smaller numbers of chemical data; the last
two are suitable even for a larger numbers of chemical data.
REFERENCE
Domenico, P. F., 1976. Physical and Chemical Hydrogeology. John Wiley and Sons. New York 824p.
Fetter, C. W., 1994. Applied Hydrogeology. Prentice Hall, Inc. Englewood Cliffs, New Jersey, U.S.A. 3
rd
Edition. 426p.
Freeze, R. A., and Cherry, J. A., 1979. Groundwater. Prentice Hall, Inc. Englewood Cliffs, New Jersey, U.S.A.
604p.
Hem, J. D., 1970. Study and interpretation of the chemical characteristics of natural water. 2
nd
Edition. Us.
Geological Survey water supply paper 1473. 268p.
Oluwasemire, B. O., 1998. Graphical technique of presenting hydrochemical data. (unpublished) B.Sc. Seminar
Department of Geology, University of Maiduguri. 33p.
Piper, A. M., 1944. A graphical procedure in the geochemical interpretation of water analyses. Trans. Amer
Geophysics Union Pp 914-923.
Schoeller, H., 1962. Leseaux Souterraines. Mason and Cie. Paris 642p.
Stiff, H. A., 1951. Interpretation of Chemical water analysis by means of pattern. Journal of petrol Technology
Vol. 3 No 10 Pp 15-17.
Todd, D. K., 2004. Groundwater Hydrology. 2
nd
edition John Wiley and Sons. New York 516p.
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
71
APPENDIX
Fig. 1
Fig. 2
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
72
Fig. 3
Fig. 4
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
73
Sample A to D Pie Charts
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
74
Fig. 9
Fig. 10
Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol.5, No.4, 2015
75
Sample A to D Stiff Diagrams
Fig. 11
Fig. 12
Fig. 13
Fig. 14
The IISTE is a pioneer in the Open-Access hosting service and academic event management.
The aim of the firm is Accelerating Global Knowledge Sharing.
More information about the firm can be found on the homepage:
http://www.iiste.org
CALL FOR JOURNAL PAPERS
There are more than 30 peer-reviewed academic journals hosted under the hosting platform.
Prospective authors of journals can find the submission instruction on the following
page: http://www.iiste.org/journals/ All the journals articles are available online to the
readers all over the world without financial, legal, or technical barriers other than those
inseparable from gaining access to the internet itself. Paper version of the journals is also
available upon request of readers and authors.
MORE RESOURCES
Book publication information: http://www.iiste.org/book/
Academic conference: http://www.iiste.org/conference/upcoming-conferences-call-for-paper/
IISTE Knowledge Sharing Partners
EBSCO, Index Copernicus, Ulrich's Periodicals Directory, JournalTOCS, PKP Open
Archives Harvester, Bielefeld Academic Search Engine, Elektronische Zeitschriftenbibliothek
EZB, Open J-Gate, OCLC WorldCat, Universe Digtial Library , NewJour, Google Scholar
