BACKGROUND

Since commencement of the first Five Years Development Plan in 1969, the need for groundwater has increased in many mayor cities for a variety of purposes. For example in 1970, Jakarta used less than 10 million cubic meter of deep groundwater (JICA, 1983), whereas this figure was trippled in 1987 (Haryadi et al, 1988). The groundwater situation in other population growth centers like Medan (Sumatra), Bandung and Semarang (Java) or Denpasar (Bali) is more or less the same as in Jakarta.

The increase in the use of groundwater has already had negative impact on the environment, as recorded in Jakarta (salt water encroachment, land subsidence, lowering of the piezometric head), Bandung (lowering of the piezometric head) and Denpasar (salt water encroachment, lowering of the piezometric head). Thus , to aid anticipation of groundwater needs in urban areas and in order to minimize negative impacts, the groundwater planning map is urgently required.

CONCEPT OF THE MAP

To fulfil the above requiremnet, the map concept must first of all be elaborated in stages (Struckmeier et al, 1988):

1. definition of purpose and target group

2. requirement for the map concept

3. preparation of the map concept

1. Definition of purposes and target group

The maps and reports should be specially designed for planners and executives, who require reliable information. The maps and reports should also present groundwater information in such away that it can easily depicted for environmental planning and development purposes.

2. Requirement for the map concept

Since maps and reports have to be tailored to suit planners and executives who have no background in hydrogeology, complex hydrogeological situations have to be displayed and described on simplified maps and in as far as is possible, they should avoid professional hydrogeological terminology. In other words, both the map representation and the text of the reports are to be clear, simple , and universally understandable.

Whenever the necessary information has to be portrayed on a map in an easily perceptible way, a set of maps must be prepared in which each map clearly contains a set part of the total information content which has to be considered in the planning process.

3. Preparation of the map concept

Bearing in mind that maps are media for linking hydrogeologists and planners, the question rises as to what kind of information must be presented on the maps so that optimum results can be obtained by these experts.

From long list of features that can be presented on the maps it was concluded that for purpose in question, the possibilities of groundwater development for drinking purposes should be shown on the main map. This information is derived from map drafts showing the exploitable groundwater resources (quantity) and the suitability of groundwater for drinking purposes (quality).

In addition, useful information on other topics to be considered in environmentel planning should be portrayed on supplementary maps at smaller scales and on cross-sections.

For preparing the main map above, national map drafts at a scale of 1 : 50,000 are required and should consist of :

1. up-to-date topographic base maps

2. a master base map of the sheet area which serves as the master copy for the following sheets, i.e. :

   • location (water point) map, showing exact location of wells, boreholes, sprins, etc.

   • lithological base map

   • water level contour map or depth to groundwater level map

   • groundwater resources map (according to Struckmeier and Soetrisno, 1986) and/or borehole yield or aquifer parameter (e.g. transmissivity) map

   • hydrochemical maps

   • other specialized maps (e.g. hydrodynamics, flow system, vulnerability, etc.).

The main map

The principal aim of the main map at scale 1 : 50,000 is to present an areal assessment of the possibilities for development of groundwater for drinking purposes. The possibilities are based on two groups of criteria related to an assessment of the exploitable quantity and the chemical composition of groundwater, respectively.

Three classes of each, i.e. the quantity and th quality criteria, have been distinguished and arrange in a matrix.(Table 1)

		Good (below recommended maximum values)	Fair (between recommended and maximum values)	Poor (above maximum permissible value)
Exploitable Groundwater Resources	High	Blue
	Fair	Green		Orange
	Low	Yellow

Table 1. Matrix of suitability of groundwater for drinking purposes and exploitable groundwater resources defining 4 areal colors (after Struckmeier et al, 1988)

The exploitable quantity of groundwater is assessed on the basis of values of regional transmissivities, specific capacities and well yields (e.g less than 2 l/s, 2 - 10 l/s and more than 10 l/s ).

From the view poin of the suitability of groundwater based on its chemical composition three classes have been defined, in terms of mayor inorganic constituents only (pH, TDS and ions of Fe, Mn, Cl, NO₂, NO₃, and SO₄), according to the standards of the Department of Health(see Table 2). Good suitability indicates groundwater with values which meet the recommended Department of Health standards, fair applies for areas where drinking waater quality could be attained by simple treatment procedures, while the suitability of groundwater for drinking purposes is considered poor in areas where one or more constituents exceed the maximum permissible values and drinking water standards are not met or costly treatment is required.

	Recommended Maximum value ( mg/l )	Maximum permissible Value ( mg/l )
Fe Mn Cl NO3 NO2 SO4 pH TDS	0.1 0.05 200 - - 200 - 500	0.1 0.5 600 20 0.0 400 7.5 1500

Table 2. Drinking water standards of Department of Helth for ions of Fe, Mn, Cl, NO₂, NO₃, and SO₄ (after Struckmeier et al, 1988)

The main map entitled "Possibilities of Groundwater Development for Drinking Purposes" distinguishes four different classes which are shown by color :

• b l u e  = good

• green   = fair

• yellow  = poor

• orange = no

In the less favorable areas, i.e. fair, poor, and no, colored stripes are shown in places where better condition occur at depth. In addition, areas where intensive groundwater abstraction takes place are shown to avoid misinterpretation of the map

Complementary maps and sections

Useful complementary information that should be considered in the planning process is presented on additional maps. Complementary maps give additional information about groundwater and general hydrogeology, i.e. :

• land use and constraints map related to groundwater exploitation, scale 1 : 100,000

• depth to groundwaater level map, scale 1 : 100,000

• hydrogeological sketch map, scale 1 : 250,000

• hydrogeological cross-sections

DISCUSSION : GROUNDWATER PLANNING MAP FOR GREATER BANDUNG

Since the groundwater data and related data available for this area suffice, field work has been done mainly for data confirmation and collection of the latest data only.

During implementation of the concept, several constraints were encountered. These were not from the concept inself, but mostly from external factors like collecting the latest data on land use maps, airphotos or updated topographic maps and which came from other institutions. However, after experiences from field work in other areas, minor changes of the map concept have been effected.

In general, as a test of the concept for Greater Bandung and for other cities which have different hydrogeological conditions the results are good.

General Information on Greater Bandung

Bandung is the capital of West Java Province and has population of almost 1.5 million (19860, with a population growth of 1.8 % between 1980 to 1985.

Bandung lies on a plateau that has an elevation of between 700 m and 1,100 m above sea level and is surrounded by a mountain range and strato-volcanoes which are Mt. Tangkubanparahu (2,093 m) in the north and Mt. Malabar (2,350 m) in the south. This area is also known as the Bandung basin.

The Citarum river is the only river that drains the intermontane basin of Bandung.

The average rainfall for this area is 1500 - 2000 mm/year (Anonymous, 1973), with air temperature of 16.7 C^o minimum and 29.3 C^o maximum, whereas humidity ranges between 59 to 85 %.

The use of groundwater in Greater Bandung has greatly accelerated, conforming to the rise in its population. In the 1970's, the city water supply tapped 40 l/sec groundwater from 12 artesian wells, while industries, primarily textile manufactures consumed an estimated additional 300 - 400 l/sec of water from private wells.

In 1986, Suyono established that the total abstraction of groundwater in Bandung basin rose to 1,130 l/sec or three times that of nearly two decades ago. However, the water supply situation in Greater Bandung is still critical. Ruchijat et al, 1988, noted that the city water supply system produced 1,650 l/sec. Of that, 37 % originated from the water supply system, while the rest of the population was supplied by other sources.

With reference to water supply planning for 1990, Greater Bandung will need 2,648 l/sec or 1,000 l/sec more than at present. Due to the role of groundwater as a resource the city water supply system of Greater Bandung, the groundwater planning map will help the city water supply planners to meet the 1990 requirement.

Hydrogeology

In the Bandung area, the material is from two sources. The oldest rocks cropping out in this area are those from the hypothetical Sunda volcano of presumably late to middle Pleistocene age. The rocks are breccias and lavas, some of which are very dense. Remnants of the sunda volcano can be seen as scaterred mountain blocks around Lembang, north of Bandung.

Part of the Sunda material was covered by younger material from Mt. Tangkubanparahu, at a time in which its activity was severe and produce huge amounts of pumicious tuffs that covered extensive areas. Bandung is built on the periphery of this tuff fan. During this period of activity, Lake Bandung was formed as a result of the damming of the Citarum river. The highest level attained by the lake water was 722 m above sea level (Purbo-Hadiwidjojo and Sukardi, 1974). When spilling took place the lake was gradually drained until finally, the present day Bandung plateau was formed.

After this period, the volcano produced basalt flows which followed several valleys and then ceased its activity by producing pyroclastics.

As can be expected in such unsorted materials, there are no well defined aquifers and no layers of uniform composition that are spread over large areas. Consequently, there are great variation in hydraulic properties from place to place and in depth. However, for planning purposes and simplification, generalisation of the aquifer in Bandung basin can be made as follows:
Three main aquifers were identified by drilling: a shallow aquifer down to approx. 35 m, intermediate aquifers between approx. 45 m and 90 m, and a deep aquifer below 100m. The aquifers are heterogenous in their composition and show vertical and horizontal variations. In general, it may be assumed that no direct and critical connections exist beeetween the shallow and deeper aquifer (Anonymous, 1980). However, in the eastern part of the basin where many textile indusrties are located, a lowering of the water table of private dug wells adjacent to deep wells of these industries is evident.

The distribution of the transmissivity values of the deep system indicates that the transmissivity of the central part of the basin is relatively high, ranging from 500 m²/day to more than 1500 m²/day.

The aquifers of the central part of the basin are highly productive with well yields more than 10 l/sec. This area is bound in the east and west by zones of low transmissivity values of less than 250 m²/day and classified as productive to moderately productive, where well yields are less than 10 l/sec (Soetrisno, 1983).

The volume of groundwater flow from the north into the Bandung basin is roughly estimated 71 million m³/year (Bender, 1981).

The shallow groundwater is already locally polluted, particularly within the city of Bandung, where the sewerage is generally poor. In this area the water quality of the shallow aquifer undergoes significant changes which obviously derive from pollution, indicated by high nitrite content. The mineralisation increases and conductivities up to 1,000 micromhos are reached in the southern section of Bandung.

The chemical composition of deep groundwater surprisingly indicates low SO₄ content, though shulpur was expected to be endemic and abundant, due to volcanic activity; the content of Fe and Mn is generally low. However, the deeper layers may yield water with rather high iron and manganese contents. Obviously, there is no significant contamination of the deep groundwater system. However, several wells in the eastern and southern part of basin yield water with a high nitrite content which is presumably due to leakage from shallow aquifers.

With reference to the drinking standard quality of the Departmnet of Health, deep groundawter in Greater Bandung is generally classified as fair to good quality for drinking purposes, while shallow groundwater in several locations is considered poor.

The main map

The map of possibilities of groundwater development for drinking purposes for Greater Bandung (Ruchijat et al, 1988) has been prepared basing on the matrix of water resources and the suitability of groundwater for drinking purposes in Greater Bandung previously explained.

There are four classes of possibilities :

1. Good possibility (blue color), where groundwater resources may yield more than 10 l/sec with good quality. However, since groundwater is already exploited intensively, mostly for textile industries and city water supply, extra boreholes should be sited carefully. The area with good possibility extends from Cimahi, northwest of Bandung, to the heart of Bandung city itself.

2. Fair possibility (green color), where groundwater resources may yield 2 - 10 l/sec, with good to fair quality.
   Area of fair possibility occupies an extensive area of Greater Bandung, in the center of the basin, and Lembang plateau, north of Bandung. In several locations like Cicaheum to Ujungberung east of the city and Dayeuhkolot south of the city where many textile industries are located, the use of groundwater is already intensive.

3. Poor possibility (yellow color), where groundwater resources may yield less than 2 l/sec, with good to fair quality.
   Area of poor possibility covers the montainous area of Greater Bandung.

4. No possibility (orange color), where the quality of groundwater is poor, even at greter depths.
   The areas near Cicaheum and Dayeuhkolot which are the most densely populated areas of the city and the areas close to garbage dumps in the north and south of Bandung, are included in this class.

Apart from the classes above, in several areas of Greater Bandung the better possibilities for groundwater development for drinking purposes occur at depth, whereas no possibility exist in the upper part (vertical colored). Those areas are comprised south of Cimahi, northeast Dayeuhkolot, and north of Majalaya in the eastern part of the basin.

Complementary maps and cross sections

Complementary maps and cross-sections present additional information related to groundwater, in order to provide additional information to the planners.

Land use and constraints related to groundwater exploration, scale 1 : 100,000.

For two decades, a great change in land use has taken place in the Bandung basin. The areas which were formerly paddy fields are now housing complexes or industrial sites. The mountainous area may be the only part of Greater Bandung which is relatively unchanged in terms of land use.

Thus increased risk of groundwater pollution from water and sewage water in housing areas might be the greater constraint in the Bandung basin. The situation has become worse as sewerage in Bandung is generally poor, particularly in densely populated area.

The other constraints come from industrial waste and garbage disposal, while intensive use of fertilizers might occur in Lembang and in paddy fields in the eastern part of the basin.

Information on important constructions which are potential sources of groundwater pollution like quarries, the airport and storage tanks are also depicted on the map.

Depth to groundwater level map, scale 1 : 100,000

The depth to groundwater table in the northern Bandung basin ranges between 5 and 6 m, in area of elevation lower than 700 m above sea level, and becomes shallower southward.

West of Bandung, at the approximate center of the tuff fan, the piezometric level was reported to be about 10 m above terrain surface in the 1970's. However, due to high abstraction of groundwater in the last decade, the piezometric level is down to 20 m below terrain surface level. The lowering of the piezometric head was expressed by the existence of cones of depressions which are recorded in the western part of Bandung. A cone depression is also observed in the east and south of Bandung, and mostly associated with textile industries.

Hydrogeological sketch map, scale 1 : 250,000

The map serves as a global overview of groundwater occurrence in the entire basin, related to its morphology.

There are two groundwater regions in Greater Bandung, which are :

• Groundwater region of the intermontane basin, an area of elevations 700 m above sea level.

• Groundwater region of strato-volcanoes, occupying mountainous area surrounding the plateau.

The map also indicates that the groundwater regime boundary does not necessarily coincide with the administration boundary.

Hydrogeological cross-sections

Two hydrogeological cross-sections have been constructed, one section stretches from Lembang in the north to Banjaran in the south, whereas the other section extends from Cimahi in the west to Cicalengka in the east.

These sections show that the Bandung basin contains a multi-layer aquifer system with several discontinuous aquifers being heterogenous in thickness in horizontally and vertically directions, as previously discussed.

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Reference: 

1. Anonymous, 1980, Factual Report No.3 Hydrogeology, Bandung WaterSupply Project, German Water Engineering - Ministry of Public Works, Jakarta. 

2. Anonymous, 1973, Rainfall Atlas of Indonesia Vol. I, Meteorological Note No.9, Department of Communications, Jakarta.  

3. Bender H., 1981, Contribution to the Hydrogeology of the Bandung Basin, Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover.  

4. Haryadi, Djaendi dan Harnandi D., 1988, Survei Penyusupan Air Asin di Daerah Jabotabek, Direktorat Geologi Tata Lingkungan, Bandung. 

5. Purbo-Hadiwidjojo M.M., and Soekardi R., 1974, Groundwater Potential of Areas Underlain by Volcanoclastic Rocks: Example from Indonesia, Geological Survey of Indonesia, Bandung.  

6.Ruchijat S., Denny B.R., dan Arief S., 1988, Survei Potensi Airtanah Daerah Bandung, Direktorat Geologi Tata Lingkungan, Bandung.

7. Soetrisno S., 1983, Hydrogeological Map of Indonesia 1 : 250,000, sheet V, Bandung (Java), Directorate of Environmental Geology, Bandung.

8. Struckmeier W., Soetrisno S., and Soefner B., 1988, Concept for Groundwater Planning Maps in 5 Major Cities (Jakarta, Bandung, Semarang, Surabaya, and Denpasar), Revised version, Directorate of Environmental Geology, Bandung.

9. Strukmeier W. and Soetrisno S., 1986, General Legend for the Hydrogeological Map of Indonesia 1 : 250,000, Directorate of Environmental Geology, Bandung.

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