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26th Annual Indonesian Geologist AssociationJoin Convention Bali, 2007

Full Paper Submission

Corresponding Author: Dasapta Erwin Irawan

Address:Research Division on Applied GeologyFaculty of Earth Science and TechnologyInstitut Teknologi BandungBasic Science building 3

thfloor

Jl. Ganesa no 10, Bandung - 40132

Email:[email protected],Tel/Fax: 022-251 0802

Title of paper:Outlining Hydrogeological System using Multivariate Analysis on Groundwater Quality at Mt.Ciremai, West Java, Indonesia

Author(s) and Affiliations1. D. Erwin Irawan2. Deny Juanda PuradimajaResearch Group on Applied Geology, Faculty of Earth Sciences and Technology,Institut Teknologi Bandung, Jl. Ganesha No. 10, 40132 Bandung, Indonesia (e-mail: [email protected])3. Sudarto NotosiswoyoResearch Group on Earth Resources Exploration, Faculty of Mining and Petroleum Engineering,Institut Teknologi Bandung, Jl. Ganesha No. 10, 40132 Bandung, Indonesia (e-mail:[email protected])

Abstract (no more than 200 words)

Volcanic slopes are important sources of water. Groundwater observation in east slope of Ciremai wasconducted in period of dry season of May until June 2006 on 119 springs. Fourteen variables wasmeasured: elevation, spring discharge, TDS, EC, pH, T water, T air, calcium, magnesium, chloride,sodium, sulphate, potassium, bicarbonate.

Cluster analysis has successfully extracted 3 clusters: cluster 1 (112 obs), cluster 2 (5 obs), cluster 3(2 obs). The hydrogeological schematization has been constructed based on interpretations of 3clusters. There are 3 hydrogeological systems: 1) Hydrogeological system 1 is characterized by:cluster 1, heterogeneous data, normal water temperature, TDS, EC, and major elementsconcentrations, and many chemical influences. 2) Hydrogeological system 2 is characterized by:cluster 2, homogeneous data, high water temperature, TDS, EC, the result of interaction betweennormal meteoric water and hot water of volcanic origin. 3) Hydrogeological system 3 is characterizedby: cluster 3, high water temperature, TDS, and EC with homogeneous characters, deep flow system,

and interaction with sedimentary layers of Fm. Kaliwungu.

Key words:1 Stratovolcanoes2 HydrogeologicalTracer3 Multivariate analysis
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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Outlining Hydrogeological System using Multivariate Analysis on Groundwater Quality

at Mt. Ciremai, West Java, Indonesia

D. Erwin Irawan1, Deny Juanda Puradimaja1, Sudarto Notosiswoyo2

1Research Group on Applied Geology, Faculty of Earth Sciences and Technology,

Institut Teknologi Bandung, Jl. Ganesha No. 10, 40132 Bandung, Indonesia (e-mail: [email protected])

2Research Group on Earth Resources Exploration, Faculty of Mining and Petroleum Engineering, Institut

Teknologi Bandung, Jl. Ganesha No. 10, 40132 Bandung, Indonesia (e-mail: [email protected])

Abstract

Volcanic slopes are important sources of water. Groundwater observation in east slope of

Ciremai was conducted in period of dry season of May until June 2006 on 119 springs.

Fourteen variables was measured: elevation, spring discharge, TDS, EC, pH, T water, T air,

calcium, magnesium, chloride, sodium, sulphate, potassium, bicarbonate.

Cluster analysis has successfully extracted 3 clusters: cluster 1 (112 obs), cluster 2 (5 obs),cluster 3 (2 obs). The hydrogeological schematization has been constructed based on

interpretations of 3 clusters. There are 3 hydrogeological systems: 1) Hydrogeological system

1 is characterized by: cluster 1, heterogeneous data, normal water temperature, TDS, EC, and

major elements concentrations, and many chemical influences. 2) Hydrogeological system 2

is characterized by: cluster 2, homogeneous data, high water temperature, TDS, EC, the result

of interaction between normal meteoric water and hot water of volcanic origin. 3)

Hydrogeological system 3 is characterized by: cluster 3, high water temperature, TDS, and

EC with homogeneous characters, deep flow system, and interaction with sedimentary layers

of Fm. Kaliwungu.

1. Introduction

Indonesia is a part of ring of fire, consisting of almost 128 volcanoes. In other figure, 13

17% of worlds volcanoes are located in Indonesia. Such large number of volcanoes makes

Indonesia one of important country to solve volcanoes problems. Subduction zone lies across

the country forming volcanic belt, most of it are strato volcano. Hundreds of volcanoes

produce volcanic deposit which covers 33,000 km2or one sixth of Indonesias land (Dept. of

Mining and Energy, 1979).

At this volcano, volcanic deposit plays role as productive aquifer, as shown by the emergence

of spring belt with enormous discharge and excellent quality. The aquifer comes as porous

system as well as fracture system. For an example on Mt. Ciremai, there are at least 116

springs with variable discharge, from 10 liter/seconds to 1000 liter/seconds.

This paper describes the hydrological assessment performed on the Mt. Ciremai (Figure 1).

Here we analysed 116 springs around the volcano on water quality and quantity. The results

show radial flow patterns, a dependency on slope aspect and altitude and lithology. This paper

will elaborate on the relationship between volcanic geomorphology and hydrology that was

found and discuss how this information could be used for assessing the spatial patterns of

local groundwater systems on volcanic slopes. Lastly, we make a spatial water balance to

illustrate the regional differences in water availability.


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2. Problem Statement

On the Java island Indonesia, the water demand increases due to population growth and rising

water consumption per capita (Puradimaja et.al, 2004). Although Indonesian islands receive

abundant precipitation (2000 - 4000 mm/yr), it is not well distributed both spatially and

temporarily. For example the Java Island shows large spatial differences of rainfall betweenthe coastal areas (less than 250 mm/yr) and volcanic areas (more than 2500 mm/yr). The

monsoon climate divides the year in a clear dry and wet period.

Water scarcity, especially for agriculture is a well-known problem in Indonesia. However, the

water resources are not managed yet in this respect. By example, upslope movement of

habitation and agriculture changes the water budget of that particular region and influences

the amount of stream water available downstream.

3. Literature Review

3.1 Hydrogeological SettingMount Ciremai is a solitaire-strato volcano with elevation of 3072 masl, situated at

Majalengka (west flank) and Kuningan Regency (East flank) (Figure 2), 20 km south of

Cirebon, Indonesia. It lies at 6 53 30 latitude and 10824 00 longitude. The diameter of

this volcano, from the peak to the foot slope is about 10 km. Mt. Ciremai has recorded 5

eruptions in 1698, 1772, 1775, 1805, and 1937, with 3 -112 years interval, historically. Those

eruptions produced 22 volcanic deposits, consist of: 11 lava flows, 9 pyroclastic materials,

and 2 laharic breccias. Many studies have been conducted in the area.

Situmorang (1995) has published the volcanic geological map of Mt. Ciremai. According to

the author, the exposed volcanic deposit was produced by 4 generation of eruptions, which

generated 3 types of deposits. Lava flow consists of andesite rock, black to brownish incolour. It has fractures, cooling joints and columnar joints due to mass unloading and cooling

processes. Pyroclastic materials consist of andesite fragments planted in tuff lithic and tuff

crystal. It comes in flowing and falling mechanisms. Laharic breccias consist of andesite

fragments planted in volcanic sands, tuff lithic, and tuff crystal. It comes in water dominant

flowing mechanisms. The first regional hydrogeology condition was introduced by IWACO

WASECO (1989). Regional aquifer system at Mt. Ciremai area is divided in to 3 systems:

Surficial Alluvium, Quaternary Volcanic (Young Volcanic), and Tertiary Sediment system.

More details study was conducted by Puradimaja et.al (2003). According to the author, there

are 3 main aquifer units: pyroclastic breccias, lava, and laharic breccias. All of the observed-

aquifers are unconfined aquifers. The aquifer feeds water to spring zone encircling Mt.

Ciremai. The spring zone is interpreted to be following slope morphology which controlled by

change of rock distribution. Such condition forms 2 slope breaks at 750 masl (4o difference)

and 1350 masl (19o difference).

Irawan (2006) stated that there 3 factors which control the spring emergence. First factor is

the change of rock distribution from lava to laharic breccias. Morphological features in form

of ridges and valleys also contribute to control groundwater flow pattern. Second factor is

fracture and continuous voids zone controls the level of spring discharge in volcanic terrain.

Third factor is the weathering processes in the study area is very intensive, resulting in thick

residual soil and high final infiltration rate, which is very potential to store and to be

infiltrated by rain water and surface water.There were 3 thermal groups of spring, based on 23 spring observations, consists of:

hypothermic, mesothermic, and hyperthermic (Figure 3). Based on the thermal classification,


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it can be interpreted that thermal differences were triggered by interaction between

groundwater temperature and environmental temperature. The hypothermic group shows the

closed system of groundwater. Mesothermic group shows the interaction between

groundwater and surface temperature. Hyperthermic groups were characterized by the

interaction of groundwater with specific subsurface heat source. (Hem, 1970 and Matthess,

1982). Piper plot is presented in Figure 4, to show the differentiation of chemical characters.

The intensity of weathering processes in the study area is very high, indicated by 2 m tonearly 10 m of soil thickness. Such thick residual soil is very potential to store and to infiltrate

rain and surface water in to the aquifer. Infiltration tests (according to Chow et.al. 1964;

Miyazaki, 1993) was carried out to verify the final infiltration rate of residual soils. Residual

soil from lahars shows the largest values of 1.26 2.53 cm/min, followed by residual soil

from pyroclastic breccias 1.5 cm/min, and from lava flow 0.5 1.2 cm/min. High final

infiltration rate (Linsley & Franzini, 1978) indicates the high capacity of residual soil to be

infiltrated by rain water and surface water.

Subsequently, in 2002, Bapeda Kuningan Regency has mapped 161 springs with total of

8285.2 l/sec. The result is five classes of spring discharge magnitude (Meinzer 1923, op.cit

Todd, 1980): Six springs of Class II (4%), 44 springs of Class III (27%), 15 springs of ClassIV (9%), 40 springs of Class V (25%), 56 springs of Class VI (35%). Both preceding studies

have not analysed the control of geological setting to groundwater springs.

3.2 Cluster Analysis

Cluster analysis is an unsupervised-multivariate statistical method that identifies the

hierarchial structure of similarity of large number observations in to into groups. Thus, that

the objects within a group are very similar and objects from different groups are significantly

different in their characteristics (Smith, 2002). There are 3 steps in cluster analysis (McGraw-

Hill, 2007)

Step 1: Select cluster variables and distance measures. How many and which variables are to

be selected will affect the analysis results. In cluster analysis, it is implicitly assumed

that every variable is equally important.

Step 2: Select cluster algorithm. Cluster algorithm is the procedure to determine clusters,

or groups. There are two categories of cluster algorithms, hierarchical and non-

hierarchical. In this paper, we are going to use hierarchical algorithms.

Step 3: Perform cluster analysis. Cluster analysis will determine the cluster structure

specifically, which objects form a cluster, how many clusters, the features of clusters,

etc.

Step 4: Interpretation. We need to explain what these clusters mean and how should wename and make sense of these clusters. The interpretation is based on geological

facts.

According to McGraw-Hill (2007), in cluster analysis, distance is used to represent how

close each pair of objects is. The most common distance measurement is Euclidean Distance

(Figure 6). The Euclidean distance between any two objects, that is, the distance between

object i and object k(dik), is

N

j

kjijik xxd

1

2)( Equation 1


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In cluster analysis, it is desirable that the distances between objects within a cluster (group)

are small and the distances between different clusters are large, as illustrated in Figure 6. The

definition of the distance between clusters depends on the methods to determined relationship

between clusters, called linkage. There are several different linkage methods which we will

discuss as follows. In single linkage method, the distance between two clusters is defined to

be the distance of the nearest neighbours (Figure 6). Specifically, assume that we have two

clusters, clusterR and cluster S. Let rrepresent any element in cluster R, and let s representany element in cluster S. Then the distance between cluster R and cluster S in single linkage

method is defined as

SsRrdd rsSR ,min))(( Equation 2

In a dendogram, the distances between clusters and the joining process are described very

well. We usually want to form more than a cluster in further analysis. As we discussed earlier,

a good clustering should be as follows:

1. The objects within a cluster should be similar one another, in other words, the distances

between the objects within a cluster should be small.

2. The objects from different clusters should be dissimilar, significantly, or the distancesbetween them should be large.

4. Methodology

The delineation of groundwater systems aims: 1). the recognition of the hydrogeological

boundaries enclosing the system; 2) the mechanisms of recharge, and discharge, along with

the flow paths of groundwater from recharge areas to discharge areas Mandel & Shiftan

(1981). In order to map the hydrogeological boundaries and rechargedischarge mechanism,

this research used 3 main approaches: desk study, hydrogeological mapping, hydrochemical

sampling and analysis. Detailed work describes as follows.

1) Desk study: The desk study consisted of studying the topographical map, geological maps,

hydrogeological maps, and re-analyses of previous studies;

2) Hydrogeological mapping: The hydrogeological mapping is based spring observations;

consist of: coordinates, local geological observations, measurement of the spring

discharges and the water qualities. The discharge was measured using the area-velocity

method. The water velocity was measured using current meter. For small discharge (less

then 1 l/s), the measurements were taken using volumetric method with a 10 liter bucket

and stopwatch. Duplets measurements were taken at each observation.

3) Hydrochemical sampling: At each location, physical parameters measurements were takenconsist of: air temperature, water temperature, Electro-Conductivity (EC), Total Dissolved

Solids (TDS), and pH. The air temperature was measured only during sampling using a

standard thermometer, while other above parameters were measured using Lutron portable

equipment. For laboratory chemical analysis, the spring water was sampled using 1 litre

plastic bottles. The duplets laboratory analysis comprises: the calculation of major

elements concentrations using titration method. Chemical test results have to be validated

using ion balance equation (see equation 3), before further analyses. We determined 20%

error balances as permit-able limit. Samples have higher than 20% of error balance will be

re-tested while samples have lower than 20% error will be analyzed.

[( cations - anions) / ( cations + anions)] x 100% equation 3


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4) Statistical analysis: The hydrochemical parameters and the result from field observations

were analyzed using basic statistical analysis and cluster analysis to assist the

hydrogeological analysis, by using Minitab (trial version).

5) Interpretation: The interpretation aims to schematization of hydrogeological system based

on each spring clustering.

5. Analysis and Interpretations

The survey was conducted in period of May until June 2006, in dry season. As much as 119

springs from east slope. At each spring, there were 14 variables measurements (see Table 3):

Elevation (Elev) in masl, Discharge (Q) in liter/sec, Total Dissolved Solids (TDS) in ppm,

Electro Conductivity (EC) in micro Siemens/cm, Acidity (pH), Water temperature (W.temp)

(oC), Air temperature (A. temp) in oC, Major elements concentration (mg/l): calcium (Ca2+

),

magnesium (Mg2+

), chloride (Cl-), sodium (Na

+), sulfate (SO4

2-), potassium (K

+), bicarbonate

(HCO3-).

Large deviations as shown by several variables: TDS, EC, hardness, chloride, sodium, andbicarbonate. This should affect to the clusters. Observations with maximum value of those

variables should separate relatively from the other observations with normal value. In this

section, we are going to discuss the spring clustering and dominant variables which control

the springs.

5.1 Cluster Analysis

Cluster analysis, with Minitab (trial version) has successfully extracted 3 clusters. Cluster 1

consists of 112 observations, cluster 2 comprises 5 observations, cluster 3 consists of 2

observations (see table 4 and figure 7). Cluster 1 shows more variation as shown by the large

maximum distance from centroid (9.23), relatively to cluster 2 (3.05).

5.2 Outlining Hydrogeological Systems

The outline of hydrogeological system is based on schematization of 3 clusters. The

interpretations lead to 3 hydrogeological systems (Figure 8): Hgl 1, Hgl 2, and Hgl 3.

Hydrogeological system 1 (Hgl 1 112 obs) is characterized by large variations of data with

normal values of water temperature, TDS, EC, and major elements concentrations. This

condition is due to the many chemical influences as the groundwater flow from recharge area

to discharge area in unconfined aquifer system of 3 lithological type (from up to down):

pyroclastic breccias, lava, and laharic breccias.Hydrogeological system 2 (Hgl 2 5 obs) is described as more homogeneous observations

with anomalous values: high water temperature, TDS, and EC. The groundwater is interpreted

as the result of interaction between normal meteoric water and hot water of volcanic origin.

Hydrogeological system 3 (Hgl 3 2 obs) is separated by other 2 clusters due to the

homogeneous characters (spring number 65 and 100) with deeper flow system, compared to

Hgl 2. The 2 springs, Cikalamayan (65) and Liang Panas (100), have high concentrations of

chloride along with high water temperature. Major elements concentration is interpreted to

be the effect of interaction between hot water with sedimentary layers of Fm. Kaliwungu,

which deposited in sea environment. Layers of sand and clay in the formation below

Ciremais volcanic deposits, contribute to the high chloride content in the groundwatersamples.


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6. Conclusions

Cluster analysis has successfully extracted 3 clusters: cluster 1 (112 obs), cluster 2 (5 obs),

cluster 3 (2 obs). The hydrogeological schematization has been constructed based on

interpretations of 3 clusters. There are 3 hydrogeological systems: 1) Hydrogeological system

1 (Hgl 1112 obs) is characterized by: heterogeneous data, normal water temperature, TDS,

EC, and major elements concentrations. This condition is due to the many chemical

influences as the groundwater flow from recharge area to discharge area in unconfined aquifersystem. 2) Hydrogeological system 2 (Hgl 2 5 obs) is characterized by: homogeneous data,

high water temperature, TDS, EC. The groundwater is interpreted as the result of interaction

between normal meteoric water and hot water of volcanic origin. 3) Hydrogeological system 3

(Hgl 3 2 obs) is characterized by: homogeneous characters with deeper flow system. High

concentrations of chloride along with high water temperature are interpreted to be the effect

of interaction between hot water with sedimentary layers of Fm. Kaliwungu, which deposited

in sea environment.

Acknowledgement

The authors would like to thank The Board for Regional Planning Kab. Kuningan for

facilitating data and Director of PDAM Kab. Kuningan for access to spring abstraction site.

We also would like to thank our team of undergraduate students that gave their time and effort

to help us surveying spring data and gathering the first level analysis.


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References

Bapeda Kuningan, 2002, Inventarisasi Mataair Kab. Kuningan, Bapeda Kuningan.

Chow, 1964, Soil Water, Prentice-Hall.

Costello, A.B. and Osborne, J.W., 2005, Best Practices in Exploratory Factor Analysis: FourRecommendations for Getting the Most From Your Analysis, Practical

Assessment Research & Evaluation, Vol 10, No 7.

Dept. Pertambangan dan Energi, 1979, Data Dasar Gunungapi Indonesia, Dept. Pertambangan

dan Energi.

Hem. J.D., 1973, Study and Interpretation of Natural Water, USGS Water Supply Paper.

Irawan, D.E. and Puradimaja, D.J., 2006, The Differentiation of Hyperthermal Groundwater

Origin by using Multivariate Statistics on Water Chemistry, Journal Geoaplika,

vol 1, no 2.

Irawan, D.E.and Puradimaja, D.J., 2006, The Hydrogeology of The Volcanic Spring Belt,East Slope of Gunung Ciremai, West Java, Indonesia, Proceeding of IAEG

Conference.

IWACO WASECO, 1989, Kuningan Regency Provincial Water Supply Report, Dept. of

Public Works.

Kitano, Y. (ed), 1975, Geochemistry of Water, Benchmark Paper in Geology, Hutchinson &

Ross, Pennsylvania, pp. 273296.

Linsley, R.K., Franzini, J.B., Freyberg, D.L., Tchobanoglus, G., 1992, Water resources

engineering, McGraw-Hill, New York.

Mandel and Shiftan, 1981, Groundwater resources: Investigation and Development,

Academic Press.

Matthess, G., 1982, Properties of Groundwater, McGraw-Hill.

Miyazaki, T., 1993, Groundwater Basin Management, Tokai University Press

Multivariate Statistical Methods and Quality, Downloaded from Digital Engineering Library

@ McGraw-Hill (www.digitalengineeringlibrary.com), McGraw-Hill.

Puradimaja, D.E., Sukarno, I., Abidin, Z., Irawan, D.E., 2002, Sistem Pengembangan dan

Pengusahaan Air Bersih di Jawa Barat. Potensi dan Pola Bisnis Air Bersih serta

Air Minum, Dipresentasikan pada acara Seminar Pemanfaatan dan Pengelolaan

Air Bersih Guna Meningkatkan Kesehatan Masyarakat Jawa Barat Menuju Era

Globalisasi, Aula Barat ITB, 22 Nopember 2002.

Puradimaja, D.J, Irawan, D.E., Hutasoit, L.M., 2003, The Influence of Hydrogeological

Factors on Variations of Volcanic Spring Distribution, Spring Discharge, and

Groundwater Flow Pattern, Bulletin of Geology, Vol 35, No 1/2003, pp: 1523,

ISSN: 0126-3498.

Situmorang, 1995, Peta Geologi Gunung Ciremai, Direktorat Vulkanologi.

Smith, L.I., 2002, A Tutorial on Cluster Analysis, downloaded from

http://www.cs.montana.edu.


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Figures and tables

Figure 1 The location map of Mt. Ciremai. Box marks the study area. The area is moreless20 km south from Cirebon, West Java.

Scale 1 :

Locati


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Figure 3 Chart of thermal gradient of groundwater at Ciremai (Puradimaja, D.J., et.al. 2003).

Figure 4 Piper plots of chemical composition (Puradimaja, et.al, 2003).

K L A S I F I K A S I T E R M A L M A T A A I R

y = 4 0 9 3 . 4 0 9 - 1 5 2 . 6 9 9 * x

T A

E

1 12 1

3 24 3

5 3

6 37 38 39 3

1 2 3

1 4 3

1 5 3 1 6 31 7 3

1 8 3 1 9 32 0 3

2 1 12 2 1

1 0 2 1 1 2

2 3 32 4 3

2 5 3

2 0 0

4 0 0

6 0 0

8 0 0

1 0 0 0

1 2 0 0

1 4 0 0

k e lo m p o k m e s o t e r m a l

k e lo m p o k h i p o t e r m a l k e lo m p o k h i p e r t e r m a l

k e lo m p o k h i p e r t e r m a lTransition zone

Elevation

(masl)

Water Temperature (oC)

R2=0,81

Mg

Ca

100

0

0

100

Cl

SO4

0

100

100

0

SO

+C

l

4

Ca+Mg

Na+K

100

100

0

100

0

CO

+

HCO

3

3

100

0

0

2

4

67

89

2

4

4

6

6

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7

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9

1

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GEOLOGICALMAP

HYDROGEOLOGICALMAP

HYDROGEOLOGICALSURVEY

SPRINGOBSERVATION

PHYSICO-CHEMICAL

MEASUREMENTS

CLUSTERANALYSIS

INTERPRETATION

Table 1 Characteristics of various multivariate analyses

Method Interdependencevs. dependence

Exploratory vs.confirmatory

Metric vs.non metric

Objectives

Principal ComponentAnalysis

interdependence Exploratory Metric Dimension reduction

Exploratory Factor

Analysis

interdependence Confirmatory Metric Understand correlation

patterns, uncover latent

traits

Multidimensional

Scaling

interdependence Exploratory Metric or non

metric

Verify measurement

model

Cluster Analysis interdependence Exploratory Metric or non

metric

Create spatial

representation from

object similarities

Canonical Correlation dependence Exploratory Metric Explain covariationbetween 2 sets multiple

variables

Analysis of Variance dependence Confirmatory Metric andnon metric

Special case ofcanonical correlation

with discrete X

variables.

Discriminant

Analysis

dependence Exploratory or

confirmatory

Metric and

non metric

Special case of

canonical correlation

with discrete Y

variables.

Figure 5 The work flow of the research


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Table 2 Laboratorymethods for major element measurements

No Parameters Units Methods

1 Hardness (CaCO3) mg/l SMEWW 2340-C

2 Calcium (Ca2+) mg/l SMEWW 3500-Ca

3 Magnesium (Mg2+) mg/l SMEWW 3500-Mg

4 Chloride (Cl-) mg/l SMEWW 4500-Cl

5 Sodium (Na+) mg/l SMEWW 4500-Na

6 Sulphate (SO42-) mg/l SMEWW4500-SO4

7 Potassium (K+) mg/l SMEWW 3500-K

8 Bicarbonate (HCO3-) mg/l SNI 06-2420

Figure 6 Illustration of what is Euclidean distance (upper left), cluster distance and between

cluster distance (upper right), and dendogram as the final results of cluster analysis (lower).


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Table 3 Descriptive analysis of the variables. Large deviations as shown by several variables:

TDS, EC, hardness, chloride, sodium, and bicarbonate should affect the clustering processes.

Observations with maximum value of those variables should separated relatively from the

other observations with normal value.

Variable Mean StDev Minimum Maximum

Elevation (Masl) 491.6 237 111 1273

Discharge (Q) (l/s) 17.522 8.6 1.3 40.3

TDS (ppm) 159.6 221.7 16 1001

EC (mS/cm) 130.3 102.8 16.3 515.5

pH 7.221 0.6 6.2 9

W.temp 25.635 4.4 18.4 61.4

A.temp 28.581 3.1 21.5 42

Hardness (CaCO3) 144.4 331.7 28.2 2488.8

Calcium (Ca2+

) 26.07 39.5 8 283.4

Magnesium (Mg2+

) 21.87 61.5 1.4 432

Chloride (Cl-) 564 2536 2 13100

Sodium (Na+) 426 1916 5 10000

Sulfate (SO42-

) 14.34 23 0 120

Potassium (K+) 13.96 41 2 210

Bicarbonate (HCO3-) 181.9 409.5 12 2098.4

Table 4 Cluster analysis results (Minitab trial version). Centroid is the focal point of cluster.

Maximum distance of observation from centroid is measured on each cluster. Cluster 1 shows

more variation as shown by the large maximum distance from centroid (9.23), relatively to

cluster 2 (3.05).

Average Maximum

distance distance

Cluster basics description Number of from from

observations centroid centroid

Cluster1 112 1.99 9.23Cluster2 5 1.55 3.05

Cluster3 2 0 0

Centroid distance

Cluster1 Cluster2 Cluster3

Cluster1 0 13.97 15.68

Cluster2 13.97 0 9.28

Cluster3 15.68 9.28 0


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V48

V29

V86

V84

V85

V56

V65

V106

V108

V9

V76

V67

V38

V105

V94

V77

V101

V107

V104

V54

V98

V128

V62

V134

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V10

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V5

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V11

V26

V19

V39

V37

V88

V40

V68

V70

V64

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V52

V109

V31

Cluster 1 (continuation)

(112 obs)

Cluster 2

(5 obs)

Cluster 3

(2 obs)

V100

V14

V59

V81

V96

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V95

V35

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V2

V1

V42

V12

V23

V50

V8

V43

V49

V16

26,38

50,92

75,46

100,00

Observations

Similarity

Cluster 1 (continuation)

(112 obs)

Figure 7 Dendogram of cluster analysis (Minitab trial version). The lower dendogram is the

continuation of the upper dendogram. There are 3 clusters: cluster 1 (112 observations. cluster

2 (5 observations). and cluster 3 (2 observations).


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0

500

1000

1500

2000

2500

3000

3500

108.15 108.2 108.25 108.3 108.35 108.4 108.45 108.5 108.55 108.6 108.65

Elevasi

Hgl 1

Normal waterdescent

Tertiary sedim ents

0

500

1000

1500

2000

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3000

3500

108.15 108.2 108.25 108.3 108.35 108.4 108.45 108.5 108.55 108.6 108.65

Elevasi

Hgl 2Hot water rising

Normal waterdescent

Tertiary sedim ents

Figure 8 The schematization of 3 hydrogeological systems. The schematization is based on

interpretations of 3 clusters, lead to 3 hydrogeological systems: Hgl 1, Hgl 2, and Hgl 3. Hgl 1

is volcanic-meteoric type groundwater, Hgl 2 is volcanic-transition type groundwater, Hgl 3 issedimentary-formation type groundwater.

0

500

1000

1500

2000

2500

3000

3500

108.15 108.2 108.25 108.3 108.35 108.4 108.45 108.5 108.55 108.6 108.65

Elevasi

Normal waterdescent

Hgl 3Tertiary sediments

pdf 2007 erwin ciremai bali

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