Newsletter and Technical Publications
<Technology Needs for Lake Management in Indonesia -
Investigation of Rawa Danau and Rawa Pening, Java>
F. Demands for Water from Rawa Danau
1. Demands for water on the north coast of West Jawa
The greatest pressure for water from Rawa Danau comes from the Krakatau Steel Group in Cilegon. This group of major industrial companies is involved at present in an expansion program, which should see the development of petrochemical complexes and other industries as well as steel production. Information comes from staff of Krakatau Steel and from the JICA report on the Feasibility Study of the Ci Danau - Ci Banten Water Resources Development Project. The expected growth of the Complex is based on the expectations of regional and national economic growth as expressed in Repelita V.
The major users of water from Krakatau Steel will be the Krakatau Steel Industrial Estate at Anyer with 26 companies operating in 1992, Krakatau Steel itself, the Suralaya Power Station (PLN), the development of Cigaden Port, and domestic demand for new hotels and tourist facilities. The domestic demand is a major factor as a number of new ports are scheduled for development in the area and these call for hotel accommodation for travellers and others, as well as service industries. It is quite unlikely that the present level of water supply from Rawa Danau would be enough to meet the needs of the expanded Krakatau Steel group enterprises as forecast at present for the year 2010.
Port developments are scheduled for Bojonegara, Merak, Cigaden, and Banten. An official announcement in November 1997 (Jakarta Post, Nov 7, Hal 12, Quotes H. Dhanutirto), stated that Bojonegara was scheduled to become one of the three main ports in the whole of Indonesia. It appears that it is planned that Bojonegara will replace Tanjung Priok as the main port and main industrial transhipment area for the whole of West Java. Bojonegara is about 35km to the north east of Cilegon. Thus there are going to be enormous demands for water imposed on this whole region. It is not just Krakatau Steel which will need to look at all possible sources of water, it is another 200 or more industries. The supply of water for domestic use and for industrial use in this area will become an industry on its own. Industrial companies such as PT Sauhbahtera Samudera (Salim Group subsidiary) have already been established to meet this forecast demand for water.
There are other rivers in the area such as the Ci Ujung and the Ci Berang which might be used as additional sources of water for the Group. Investigation revealed that water in these rivers was already committed to use for agriculture and for other industries. The availability and use of water in this area (the north coast of Java west of Jakarta) has been the subject of several detailed investigations. One of these has been mentioned above, and the other is the Ci Ujung - Ci Durian Integrated Water Resources Study undertaken by JICA in 1992. From this and from information handouts about PT Sauhbahtera Samudera it is clear that plans are well established to construct dams on these rivers for the supply of water to industrial developments at Bojonegara and other places nearby.
If these developments proceed as scheduled there is no possibility of any water becoming available from rivers such as the Ci Ujung, the Ci Minyak, or the Ci Berang.
2. Present use of water from Rawa Danau by Krakatau Steel
The water from Rawa Danau meets the needs of the Krakatau Steel Group at present. The water is taken, not from Rawa Danau, but from the Ci Danau river two kilometres from the sea, just before the river enters the sea. A holding dam has been constructed in the valley of the Ci Danau at the coast and water is pumped by pipeline for 27 km to Cilegon. In Cilegon, the water is treated at the Krenceng Water Treatment Plant and allocated for use by industries in the Group, and to domestic use.
The Ci Danau pump station and pipeline has a capacity of 2.0 Cubic metres per second. This water supply system was completed about 1978. The Krenceng Water Treatment Plant has a capacity of about 2.0 Cubic metres per second. In 1992, at the time of the JICA Study, the Group was using an average of 0.90 Cubic metres of water per second. Krakatau Steel has access to other sources of water in Cilegon, primarily deep wells, the catchment of the Krenceng reservoir, and small rivers. These are unsatisfactory sources of supply in the long term.
3. Future predictions of demand for water
Projected demands for water by Krakatau Steel group at Cilegon by JICA, 1992, (from the Feasibility Study of the Ci Danau Ci Banten Water Resources Development Project, page 2-13) are as follows:
Projected demand in particular years in Cubic Metres per Second
Other data and estimates, from Government, put the predicted demand in 2010 at 7.14 Cubic metres per second. There is a wide range in the accuracy of estimation of this future demand.
4. Cost of water from various sources at Cilegon
There are other actual and potential sources of water for domestic and industrial use at Cilegon. However these are expensive compared with the cost of water at present and would impose an excessive burden on domestic and industrial users in Cilegon. From the 1992 JICA Study the rates are, in rupiah per cubic metre, as follows:
|Normal tariff from PDAM
It would impose a substantial financial burden on Krakatau steel to have to obtain large quantities of water from such expensive sources as de-salination plants, and would probably render many of the smaller industries uncompetitive.
The PDAM, the Local Government Water Supply Authority in Cilegon is supplied with up to 30 litres of treated water per second by Krakatau Steel. This water comes from Rawa Danau. As shown above it is sold for 500 Rp per cubic metre.
5 Assessments from the Ci Banten-Ci Danau Water Resources Development Projec
At the present time the flow of water from Rawa Danau, the capacity of the pipeline and pumping system, and the holding capacity of Krenceng Reservoir are adequate to meet the demands of the Krakatau Steel group for water. Nevertheless the group has to plan to meet the predicted needs of an expanded industrial complex, using the water resources to which it has access.
One major problem which has to be overcome is the seasonal variation in the flow of water from Rawa Danau.
The mean annual run-off in the Ci Danau river from 1980 to 1990 was 13.0 Cu.m/sec. It might be thought that this would be adequate to meet a requirement of 3.7 Cu.m/sec. However the problem lies in the seasonal variation in water flow, from over 20 Cu. m/sec in the wet season to less than 5.0 Cu.m/sec in the dry season.
While 5.0 Cu m/sec is still quite adequate to meet the JICA predictions for 2010, if not the Government estimate of demand of more than 7.0 Cu.m/sec, problems arise during drought years. During drought years the flow in the Ci Danau can fall to less than 1.0 Cu m/sec. It is at this point that additional storage capacity is essential.
Several plans are suggested in the JICA Study involving for instance raising the height of the Krenceng Reservoir to increase the volume of water which could be stored in the reservoir, and constructing other dams on the small rivers, including the Anyer and the Ci Banten. The point is made, several times, in the JICA Study that the construction of a dam at the exit from Rawa Danau would offer the cheapest solution, the easiest solution, and the greatest volume of water to be stored.
Since the JICA Study was specifically prevented from considering the Rawa Danau option, there are no details of rock structure and stability at the exit from the caldera which would assist in decision making at this point. This constraint was imposed because the caldera included a Cagar Alam, and this had to be protected by law and could not be destroyed. Flooding was considered to be likely to destroy it.
6. Impact of flooding on the swamp forest
Flooding would actually destroy the swamp forest if it were to be flooded to a depth of several metres and left permanently under water all year. This would be a guaranteed death sentence for the swamp forest. In fact it is likely that the swamp forest might be helped to regenerate if it were subjected to a limited amount of flooding in the wet season and if the water were not able to drain freely from the sediment of the caldera into the rivers during the dry season. In other words, the surface layers of the soil in the swamp forest should always be damp. It is impossible to define the optimal water regime for a swamp forest accurately, because none is left in Java, other than Rawa Danau, and no work on this aspect of their ecology has been carried out.
An environmental impact study has been undertaken by a private company (Gamma Epsilon, Pt, 1991) to assess the impact of the creation of such a dam. This study, unfortunately, tried to by-pass the issue of the conservation value of the Cagar Alam by claiming, without any evidence, that the Cagar Alam had been destroyed and therefore had no conservation value and should be flooded. Happily, this "study" was rejected by PHPA and the Asian Wetlands Bureau, as being unsatisfactory.
7. Conclusions and recommendations on the demand for water for planned industrial developments at Cilegon
1) There is a wide range in estimates of the actual demand for water in the next 20 to 30 years. It is likely that some of the estimates are excessive, as the present demand is not, apparently, at the level predicted in 1991. Therefore a mid-level prediction from the JICA study is used here.
2) The main requirement, at this stage, is for additional storage capacity, to "drought-proof" the industrial facilities against the one-in-ten-year droughts which can occur.
3) It may be feasible to supply some additional storage capacity in the Caldera, since the recommendation from this investigation will be that the primary objective of management should be to maintain the conservation value of the swamp forest. This will involve raising the water level in the swamp forest.
4) If a dam is constructed at the exit from the caldera, it should be fitted with sluice gates to ensure that water can be released from the caldera as required to meet the needs of the swamp forest. Since this will involve storing a considerable volume of water for some months into the dry season and then releasing the water gradually, this is likely to meet some of the needs of Krakatau Steel at present.
5) The exact water regime which should eventually be used will have to be worked out over a period of years in relation to the biology and regeneration of the swamp forest trees.
6) The sluice gates should be so constructed that at least 1.5 metres of water will always be retained within the caldera. This may be increased later after assessment of the effects of flooding. In other words, there should be no gates of any kind on the lower 1.5 metres of the dam constructed at the exit from the caldera.
7) While the construction of a dam at the exit from the caldera would retain water in the caldera in creating a lake, not all of the water in the lake would be available to Krakatau Steel. Much of the water would form a permanent lake similar to that which existed in the caldera 200 years ago.
8) Water available for use by Krakatau Steel would be the water which represented the difference between the wet season and dry season levels of the original lake. This might amount to about 1.0 or 1.5 metres over the surface area of the lake during the wet season.