Groundwater Resources of Indonesia and Their Management

By :

Soetrisno S.

1 Background

Water is essential for life. Without water all life on earth will be extinct. Therefore God’s gift should be managed properly for the benefit of mankind.

As stipulated on article (3) Paragraph 33 of the Indonesia Constitution of 1945, "Land and water and natural riches contained therein belong to and are controlled by the state and used for the benefit of the people", therefore the presence of groundwater in Indonesian soils must be used to meet the water demand for the benefit of the people.

In Indonesia, groundwater resources, primarily shallow groundwater, have been developed for centuries. The groundwater from the deep systems, however, was initially developed in the mid nineteenth century, after the successful deep well drilling in 1848 at Prins Hendrik fort, one of Dutch fortress in Batavia (now Jakarta). Since then, deep groundwater has become one of sources of raw water for drinking water for several towns in Java and the Government of Dutch Indies in that time needed to manage the groundwater and put into effect a series of water regulations in Java and Madura.

Now, in the era of developing of the country, populous cities serving as centres of development for services, education, tourism and other sectors are growing in the whole of Indonesia, primarily in Java. The need for water, therefore, is increasing correspondingly to the population and economic growth. Unfortunately, to meet the demand for water, there is still a need to rely on groundwater resources, and degradation, both quantity and quality of those resources is already an evidence. Therefore, proper management of groundwater is essential to ensure its availability both its quality and quantity and hence, its sustainability can be utilised for the benefit of the people of Indonesia.

This paper intends to discuss briefly groundwater management, firstly describe these resources, their occurrence and properties, and afterwards policies of groundwater management, legal aspects, implementation, and efforts to keep groundwater sustainable.

2. Occurrence

The occurrence and properties of groundwater, its origin, movement and chemical, constituents, are dependent on the geological frame work; that is, the lithology, structure and porosity of rocks and sediment through which the groundwater moves. Thus, groundwater occurrence in consolidated rocks is strikingly different from that in unconsolidated and semi-consolidated rocks. Based on studies of the mode of groundwater occurrence in various lithological rocks types and their hydraulic properties in relation to groundwater flow characteristics, the following general hydrogeological framework of the country may be distinguished :

• Area underlain by unconsolidated and semi-consolidated rocks
• Area underlain by Quaternary volcanic deposits
• Area underlain by carbonate rocks
• Area underlain by consolidated rocks

Area underlain by unconsolidated and semi-consolidated rocks

In Indonesia, the Quaternary sedimentary rocks comprising unconsolidated and semi-consolidated rocks are generally permeable enough to yield large quantities of water to wells. The unconsolidated rocks displayed by alluvial deposits are composed of gravel, sand, silt or clay that are not consolidated or hardened by mineral cement, by pressure, or by thermal alternation of the grains. The types of occurrence of gravel and sand aquifers within these unconsolidated rocks may be broadly grouped as coastal plain, intermontane basin and river valley.

Coastal plains in Indonesia vary in size from a very narrow or even fragmentary strip of the former sea floor exposed along the margin of the old land area, or it may be a vast, almost featureless plain, fringing hundreds of kilometres of coastline. Many stratigraphic units along the coastal plains grade oceanward from partly alluvial deposits into entirely marine units. This gradation is accompanied by a tendency for the sediments to become progressively finer grained. Thus, the alternating beds of clay and sand in the subsurface of coastal plains reflect migrating environments of deposition due to changing sea levels. While the bulk of the coastal plain sediments are deposited in marine environments, the upper layers may be of fluvial origin, at least in the areas bordering the land. Changing sea levels often give rise to the formation of terraces. Beach formations, and bars and dune ridges often comprise the younger portions of coastal plains.

Intermontane basins are more or less separate basins bordered by mountain ranges and may be underlain by large volume of unconsolidated rock materials derived by erosion of the surrounded mountains. Most intermontane basins in Indonesia are surrounded by volcanoes, such as the intermontane basins of Bandung, Madiun, Kediri, and Bondowoso. The coarser sediments are deposited by the larger tributaries and close to the mountain flanks; finer materials are generally carried to the lower parts of the valley. Sometimes the transition between the mountainous area and the area of smoother topography is sharp; the resulting deposition of alluvium is, therefore, concentrated chiefly at the floor of the mountains in the form of an alluvium fan. The sorting of the deposited material is relatively poor, but there is a tendency for the coarsest material to settle near the apex of the fan, while silt and clay are deposited at its base. The storage of the aquifers is vary large in comparison to those of the coastal plains. These aquifers are recharged directly from the precipitation and stream, whereas the mode of saturated flow within these unconsolidated rocks is intergranular.

Other unconsolidated rocks occur in narrow to broad river valleys. In mountainous regions the valley of stream are narrow and V-shaped in cross section. In the middle and lower parts, where longitudinal sections of the river have already acquired near equilibrium form, the erosion pattern changes from vertical to horizontal, and a broad valley may develop. Depending on the hydrogeological regime, the stream may be classified as either a meandering river or a braided river. The distribution and thickness of the coarse and fine units depend on the type of sediments carried out by the river and the geologic history of the river at the point of interest.

Area underlain by Quaternary volcanic products

The Indonesian archipelago contains one of the world’s most extensive volcanic areas, 129 active volcanoes, covering about 333,450 km² or 17.5 % of the total area of the archipelago. They extend for more than 6,000 km from the northern part of Sumatra to the Moluccas Sea.

Most Indonesian volcanoes are built up of calc-alkali rocks, that are andesitic or basaltic in character. As to material produced, this may be either loose in the form of fine or coarse ejectamenta, or solid in the form of lava-flows or domes. Prolonged activity of the central vent has given rise to the formation of bedded or strato-volcanoes. Their summits are built up of loose ejectamenta, attaining an inclination that corresponds to the angle of repose of those deposits. The middle part of the volcanic slope is covered by material that has been transported during lahar formation, that is a mud-flow containing debris and angular blocks of chiefly volcanic origin. Most of the lowest volcanic flanks are built up of flood-laid sediments consisting of volcanic debris reworked by streams from initial volcanic deposits on the upper slopes. As a result, breaks-in-slope come into existence, which indicate also the change in material composition.

Studies on mode of groundwater occurrence in strato volcanoes reveals that there is a regularity of groundwater conditions in their various parts. There is an intake zone at the higher levels along which rainwater may infiltrate into a number of different aquifers, depending on the distribution of permeability in the volcanic materials along the outcrop area. At lower levels a zone of groundwater discharge exists as groundwater emerges as seepages or springs at the foot of the slope. Between the first and the second zone there is a transition rather than a distinct boundary. Where conditions are favourable, another zone of artesian aquifer may be present. Within these Quaternary volcanic rocks, the mode of saturated flow is intergranular or both through fissures and intergranular.

Area underlain by carbonate rocks

Carbonate rocks, primarily limestone and dolomites, are widely distributed in the Indonesian Archipelago; however, they constitute only a few percent of Indonesia’s land area. In this country, limestones ranges in age between Permo-Carboniferous and Recent, but most are of Tertiary age. Quaternary coralline limestones with limited extend are scattered in the north coast of Irian Jaya, in small islands of Mollucas and Lesser Sunda Islands, Sulawesi and in some islands west of Sumatra.

In some localities in Java and Sulawesi the limestones develop as karstic terrains, high cliffs and isolated hills. Gunung Sewu in Central Java is one of the classic areas for tropical karst topography, consisting of many thousands of conical hills separated by valleys of irregular shape.

Although limestones constitute only several percent of this land area, it ranks as third among the best water-bearing formations of this country after volcaniclastics and alluvial deposits. The occurrence of groundwater in limestone is governed by the presence of secondary porosity. The groundwater is, therefore, unevenly distributed, and its potential depends mainly on the intensity of solution channelling.

As regards groundwater occurrence, two different type of limestones may be distinguished, viz. the well-bedded and karstic limestones. Their occurrence and availability differ considerably. The well-bedded limestone usually behaves as a fairly homogeneous aquifer in which groundwater is dissipated throughout the limestone itself, and throughout a complex pattern of fractures and secondary solution channels along bedding planes and other zones of primary porosity. In karstic limestone, karstification has resulted in a well-developed subterranean drainage system, whereby groundwater is restricted to joints and fractures owing to the intrinsically impermeable nature of the massive limestones.

Area underlain by consolidated rocks

The consolidated rocks under this classification include the Tertiary and Pre-Tertiary sedimentary rocks, and igneous or metamorphic rocks, which are extensively distributed along the mountainous and hilly areas forming the backbone of all larger and many smaller islands. The sedimentary rocks have undergone an intense diastrophic movement including folding, faulting or thrusting.

The consolidated sedimentary rocks are relatively impermeable, since no primary porosity of these rocks is of any value for groundwater storage. Groundwater occurs mainly in cracks, joints and bedding planes of shale, siltstone and sandstone. However, the groundwater availability is relatively small because the joints system are not well connected. Furthermore groundwater is often highly mineralised, especially in areas of dominant claystone and marl layers.

In terrain composed of igneous and metamorphic rocks, appreciable fractures generally occur within tens of meters. These structures are, however, of minor value for groundwater storage since fractures are small and often are connected. In some cases, limited groundwater may be obtained within the weathered zone of the igneous rocks.

3. Management

3.1. Policy

Based on the constitution of 1945, the policy of groundwater management in Indonesia comprises as follows :

1. Groundwater resources are God’s gift contained in Indonesia’s soils, belong to and are controlled by the state and should be used for the benefit of the people.
2. Groundwater resources have social function, and should not merely be used to gain economic profit.
3. Groundwater management is based on the philosophy of its benefit, its balance and its preservation.
4. Groundwater rights are merely water use rights, rights to get the water for certain purposes.
5. Groundwater for drinking purposes is the first priority above the other usages.

These policies are based in law and regulations for proper management of groundwater in Indonesia.

3.2. Legislation

The legislation governing groundwater resources management in Indonesia includes:

• Law No. 11 of 1974 on Water Resources Development
• Law No. 4 of 1982 on Environmental Management
• Law No. 24 of 1992 on Spatial Planning
• Government Act No. 22 of 1982 on Water Resources Management
• Presidential Decree No. 32 of 1990 on Management of Protection Areas
• Regulation of Minister of Health No. 528/Menkes/Per/XII/1982 on Ground-water Quality Relating to Health.
• Regulation of Minister of Mines and Energy No. 02.P/101/M.PE/1994 on Groundwater Management. As stipulated in this regulation, management of groundwater is defined as all efforts that cover inventory, regulating, developing, licensing, controlling, and supervising in a framework of groundwater conservation
• Decree of Director General of Geology and Mineral Resources No. 005.K/10/DDJG/1995 on Guidance of the Implementation of Management of Groundwater.

Referring to the above legislation, each province have groundwater regulation which is approved by their governor and their local parliament respectively.

As defined in paragraph (2) article 5 of the Law No. 11 of 1974 and Article 6 of the Government Act No. 22 of 1982, the management of groundwater resources is under the competence of the minister who is responsible for mines. Since groundwater is only one facet in the hydrologic cycle, actually the management of groundwater involves also competent sectors respectively, such as public works, industries, transmigration, public health etc. However, no coordinating body has been established so far for the management of the water resources integrally.

As regards groundwater protection (or water resources in general), Law No. 24 of 1992 stipulated that national spatial planning includes setting up protection zones, man-made zones, and special zones which are decided nationally. Protection zones include among others the recharge areas and areas close to the spring zone.

Law No. 24 of 1992 has already been applied in spatial planning in general including protection zoning; however, detailed regulation particularly on groundwater protection zone is still lacking. In order to maintain the sustainability of groundwater resources, such regulation is urgently required.

Violation against provisions of this legislation can be brought forward in accordance with the enforced existing regulations. Sanctions can be charged against the violator, and are carried out by the authorised agencies.

Although the management of groundwater resources in Indonesia is the responsibility of Minister of Mines and Energy, several institutions are also engaged in control and supervision of groundwater quality.

Directorate of Environmental Geology implements the management, in cooperation with the Provincial Administration, and issues permits on groundwater abstraction, conduct control and supervision on pollution and environmental damage to the groundwater.

The Directorate General of Water Resources of the Ministry of Public Works is primarily concerned with aspects on the use of groundwater for irrigation, including the groundwater quality deterioration due to over exploitation.

4. Efforts

Management includes functions of Planning, Organising, Implementing and Controlling. These functions are valid also in groundwater management.

Referring to the groundwater management as defined in the Regulation of Minister of Mines and Energy No. 02.P/101/M.PE/94, management functions may address to :

• Planning

  The first step of planning for groundwater supply is inventory of all aspects, related to occurrence, aquifer parameters, flow patterns, both quantity and quality aspects of groundwater.

  Inventory involves not only getting information from the supply side but also analysing the demand side.

• Organising

  Organisation in the groundwater management sense, is related to regulation of its usage and licensing, which involve responsible institutions.

• Implementing

  Implementing involves the implementation of planning and organising which are previously described.

  The bottom line of this function is how groundwater may be abstracted based on the technical conditions which are depicted on the licence and how much groundwater supply could meet the demand which has been planned.

• Controlling

  The success of groundwater management depends on the controlling function, including guidance to the users, and monitoring the resources.

  The need for law enforcement and conformity by the users determines the need for controlling, in order to keep groundwater resources sustainable.

5.Closing Remarks

Groundwater management should be conducted and be consistent based on management functions, in order to preserve its availability and sustainability in providing water for many purposes. However, its success is highly influenced by external factors, primarily economic strategic environment (economic growth triggers an exponential increase in water use), and socio-cultural; which is behaviour of water users in their perception of groundwater as renewable resources.

Last but not least, the integration among related institutions in groundwater management very much determines the success of the management. Therefore, groundwater should be managed wisely, integrally and holistically, in order to keep groundwater sustainable in supporting development.

Referrences

Soekardi P., and Soetrisno S., 1983, Hydrogeological Map of Indonesia, scale 1 : 2,500,000, Explanatory Note, Directorate of Environmental Geology, Bandung.

Soetrisno S., 1997, Pengelolaan Air Bawah Tanah, Buletin Informasi Lingkungan, Edisi 1 dan Edisi 2 Tahun 96/97, Departemen Pertambangan dan Energi, Jakarta.