Hydrogeological Analysis in Regional Planning of Tigaraksa City,
Tangerang, Banten, Indonesia
Deny Juanda Puradimaja
Research Group on Applied Geology, Faculty of Earth Sciences and Mineral Technology, Institut Teknologi Bandung,
Jl. Ganesha No. 10, 40132 Bandung, Indonesia (e-mail: erwin@gc.itb.ac.id)
B. Kombaitan
Research Group on Regional Planning, School of Architecture, Planning, and Policy Development, Institut Teknologi Bandung,
Jl. Ganesha No. 10, 40132 Bandung, Indonesia (e-mail: kombaitan@pl.itb.ac.id)
D. Erwin Irawan
Research Group on Applied Geology, Faculty of Earth Sciences and Mineral Technology, Institut Teknologi Bandung,
Jl. Ganesha No. 10, 40132 Bandung, Indonesia (e-mail: erwin@gc.itb.ac.id)
Keywords: groundwater basin, groundwater recharge area, regional planning
Submitted to: Jurnal Geoaplika
Abstract
Since 1980’s large scale housing has been developed at suburban areas of Jakarta to respond the needs. Tigaraksa is one of the areas, with 1.110 km2 area, 3.185.944 of population. The area then was selected as the capital of Tangerang Regency. The goal of this paper is to reconfirm the hydrogeological condition of Tangerang Regency, especially Tigaraksa area based on new data as materials to evaluate the hydrogeological role of the area. To achieve the goal, the methodology must cover surface and sub surface condition. Surface observation and geoelectrical mapping has been done to expose the hydrogeological setting as working basis for planners. It can be concluded that Tigaraksa area lies on the recharge area of Tangerang Regency. Based on hydrogeological mapping, it can be found that there are layers of porous formation exposed in the area then dipped northward. This condition shows the importance of hydrogeological considerations to spatial planning. It is essential for future regional planning to converts the area as groundwater conservation area with artificial recharge methods, without reducing its current function as capital city.
1. BACKGROUND
Since 1980’s large scale housing has been developed at suburban areas of Jakarta to respond the needs (Winarso dan Kombaitan, 1997). One of them is Tigaraksa which then be used as the capital of Tangerang Regency (Figure 1 and Table 1). The statistics of the area are 1.110 km2, 3.185.944 of population, 2869 of density.
Sustainability concept makes a bridge between today and future. Usage of natural resources without exhausting them. The balance between utilization and conservation of the natural resources.
Figure 1. Map of town distribution in Jabodetabek area (in hectares, Ha)
Table 1. List of town distribution in Jabodetabek area (in hectares, Ha)
2. OBJECTIVES
The hydrogeological and spatial planning study is objected to reconfirm the hydrogeological condition of Tangerang Regency, especially Tigaraksa area based on new data. The study will be used as materials to evaluate the appropriate step to conserve water recharge in the area.
3. METHODOLOGY
Hydrogeological condition is a combination of two main aspects: the solid and the fluid. The solid aspect comprises the material and the geometry of an aquifer and the hydraulic properties of the aquifer; while the fluid aspect involves the hydraulic behaviour of the groundwater. Therefore, two complementary methods have been carried out in this study (Figure 2):
(1). Surface mapping of volcanic aquifer system with 1 : 25.000 scale, to identify the geometry of the aquifer and the hydraulic properties of soil (unconfined aquifer). The data were obtained from observation of nearly 100 wells and 20 geoelectrical shot points.
(2). Flow net analysis, to identify the groundwater flow system. The main data is groundwater level position.
Figure 2. Flowchart of the research
4. BACKGROUND THEORIES
4.1 Sustainable Regional Planning
Planning is a decision-making process regarding “the future”. On each scale of planning process, spatial rules of the social life have been formed. In planning process preparing scenarios on community scale, firstly spatial analyses should be carried out. Several regional planning issues of new town / large-scale housing development: Peri-urbanization processes: “kotadesasi”; Productive agricultural land conversion to urban use’ Job-housing mismatch: toward a self-contained new town development; Sustainable principles: Macro level: physical suitability of such development; Micro level: land use based on land suitability analyses.
Throughout the world, spatial planning strategies focusing on the sustainable development have ecological approach. Both regional and urban planning processes have been based upon ecological issues. Each land is not suitable for every kind of land uses or is suitable for only one land use from the natural resource point of view. Two important analyses in urban planning processes: a) Supply side: development capacity analyses; b) Demand side: development needs analyses; c) Sustainable approach: balancing the demand to supply side. Development capacity analyses: a) Macro level: physical suitability of such development; b) Micro level: -> location suitability mapping: Spatial pattern of factors is sensitive to local principles -> Relative suitability of locations for specific land use categories (Figure 3).
4.2 Hydrogeological Considerations in Regional Planning
Large scale housing requires continuous supplies of water. This has been the major issue for cities and regions in Indonesia. Regional planning theories recognizes six physical parameters biotic and non biotic: slope, rock / soil, water, vegetation, earth resources, and geological hazards. Therefore, it can be noticed that planning needs to identify natural resources and potentials. The position of water in third rank suggests the critical role of water as controlling factor in regional planning. Moreover, hydrogeological condition plays important role to regional planning design, which is composed of three parts (Figure 4): hydrometeorology, hydrology or watershed, and hydrogeological basin. The technical procedures must be convergence between mapping stages as drawn on Table 2.
Figure 3. The five tasks for land classification and urban land use design (Kaiser et al., 1995)
Figure 4. The three integrated system of water (G. Castany, 1982)
Table 2. The convergence of groundwater potential evaluation in planning stages
(Deny Juanda P., 2006).
Consecutively groundwater as part of water resources needs to manage based on hydrogeological basin. Therefore groundwater management must consist of: hydrogeological mapping in various scale (regional and technical), understanding of hydrogeological character of INPUT (recharge area) – PROCESSES (flowing area) – and OUTPUT (discharge area), control on groundwater contamination (natural and man-made contamination) through optimization and groundwater conservation, and control on aquifer capacity to supply sustainable water needs (Figure 5).
Recharge area is where rain or surface water infiltrates to the aquifer. Discharge area is where many groundwater springs emerge to surface. Flowing area is where the groundwater flows from recharge to discharge area. The 3 areas are controlled by geological condition. As a result, groundwater flow differs from surface water flow. To sharpen the analysis, surface and subsurface mapping is very important (Figure 6).
Noting descriptions above, hydrogeological basin identification is strongly correlated with regional planning, recalling that hydrogeological boundaries rarely coincide with administrative boundaries (Figure 7).
Figure 5. An illustration hydrogeological basins and groundwater behaviour.
Figure 6. An illustration of the importance of hydrogeological schematization by means of surface and subsurface mapping.
Figure 7. Groundwater basin setting: hydrogeological boundaries and administrative boundaries. Aquifer 1 has local recharge-discharge system, aquifer 2 has intermediate system, and aquifer 3 has regional system (Deny Juanda P., 2006).
5. Hydrogeological System of Tigaraksa Area
Hydrogeological study has been done at Tigaraksa, the administration centre of Tangerang Regency. Based on subsurface analysis, the groundwater basin of Tangerang Regency is composed of three productive aquifers with common dip to the north (Figure 8). The aquifers consist of: the volcanic deposits of Genteng Formation, Banten Tuff Formation, and alluvium aquifer. The aquifers are located at 0 – 40 m up to more than 100 m (Table 3). In the aquifer systems, there are layers of interstitial clay deposits with thickness of 1 – 5 m, as impermeable lenses.
Table 3. Aquifer stratification.
|
|
Aquifer group |
Depth (m) |
Thickness |
Material |
|
I |
0-40 |
3-7 m |
Clay, sand, conglomerate |
|
II |
40-100 |
2-76 m |
Breccia, sand, clayish sand, tufaceous sand |
|
III |
> 100 |
8-22 m |
sand, tufaceous sand with clay intercalation |
he basal boundary is The Bojongmanik Formation with impermeable properties. River plays role as the west boundary, sea water as north boundary, and normal fault as east boundary. Based on potentiometric map, groundwater comes from the southern area of the regency, as recharge area then flows northward through Alluvium, Banten Tuff, and Genteng Formation.
From the hydrogeological boundary, it can be concluded that Tigaraksa area lies on the recharge area. Since the development of the area has not considered the hydrogeological setting, it is essential for future regional planning to converts the area as groundwater conservation area with artificial recharge methods, without reducing its current function.
There are three productive aquifers (dip to the north): he volcanic deposits of Genteng Formation, Banten Tuff Formation, and alluvium aquifer. The aquifers are located at 0 – 40 m up to more than 100 m. Layers of interstitial clay deposits with thickness of 1 – 5 m, as impermeable lenses. Based on potentiometric map, groundwater comes from the southern area of the regency. Groundwater flows northward through Alluvium, Banten Tuff, and Genteng Formation.
Figure 8. The hydrogeological setting of Tangerang Regency
6. CONCLUSION
It can be concluded that Tigaraksa area lies on the recharge area of Tangerang Regency. Based on hydrogeological mapping, it can be found that there are layers of porous formation exposed in the area then dipped northward. This condition shows the importance of hydrogeological considerations to spatial planning. It is essential for future regional planning to converts the area as groundwater conservation area with artificial recharge methods, without reducing its current function as capital city.
REFERENCES
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