Conceptual modelling for improving quality of surface water abstraction in Jakarta, Indonesia

Transcription

1 Conceptual modelling for improving quality of surface water abstraction in Jakarta, Indonesia M. ~khwan', Y.R. ~ares~, S. smith3 & J. colbourne3 'centre for Environmental & Water Engineering Research, Civil Engineering Department, University of Indonesia 2 Fluids Research Centre, School of Engineering, University of Surrey, UK 3~hames Water Research & Development, UK Abstract The problems associated with the unsatisfactory state of water supply and quality within the CitarumICiliwung catchment that feeds directly to the city of Jakarta are reported. The various complex mechanisms of waterways along with the dispersion pathways of pollutant discharges are discussed. The principal elements of a conceptual model for the watershed are introduced, which covers the upstream of the intake at Buaran Water Treatment Plant that feeds the eastern part of Jakarta. The proposed conceptual model should, in the long run, provide a valuable tool for testing the appropriateness of adopting different management strategies for cost-effective solutions. 1 Introduction One of the major problems that face large capital cities in developing countries, such as in Jakarta, Indonesia, is the inadequacy and poor quality of potable water supply. Such problem is experienced almost on a daily basis, which reveals inefficiency in water management and use of inappropriate technology. Currently, PAM Jaya (Jakarta's Dnnlung Water Company) has a production rate of 1.7 million m3/day of poor quality supplied through unreliable pipe distribution network. At this rate, about 40% of daily water demand in Jakarta are hardly met [l]. So, in order to compensate for the lack of sufficient technical and financial resources, reputable water companies from Europe, namely UK Thames Water International and the French Lyonnaise, were invited to help in setting up

2 4 River Basin Management efficient and reliable code of practice for water industry. The Thames PAM Jaya (TPJ) has therefore been initiated, in which Thames Water plc is the major shareholder, serving around 4 million people in the eastern part of the Greater Jakarta. Thames Pam Jaya has carried out several investigations in order to identify the main problems associated with supplying water to Jakarta [2]. Because of the level of complexity of the problems associated with water resources, TPJ established strong collaboration links with local authorities, ministries, universities and other water companies in Jakarta. The main aim of such collaboration is to enhance the understanding of the complex issues associated with catchment management planning and protection of water sources. In recent meetings, which involve the stakeholders of water management in the Greater Jakarta, there has been considerable concern regarding the problems associated with the poor state of supplied potable water. Preliminary indications have revealed that the main source of such poor quality is linked to high content of metals, mainly manganese and iron, at the intake of the treatment plant, namely Buaran Water Treatment Plant. This obviously poses a great obstacle in realising the dnnlung water standards set by PAM Jaya. As such, it is important to minimise the level of excessive iron and manganese in order to avoid possible long-term health hazards [3]. The aim of the paper is to address the various complex mechanisms of water motion and possible pathways of chemical dispersion processes within the catchment. Presenting the principals of a conceptual model development for the watershed, upstream of the intake point will follow thls. It is hoped that the proposed conceptual model would provide useful tool for assessing the appropriateness of various water management strategies. The province of Jakarta and its surroundings are known by Jabotabek, which comprise of (Jakarta, Bogor, Tangerang and Bekasi). The Jabotabek catchment covers a surface area of approximately 7,200 km2, of which Jakarta covers surface area of 652 km2. Jakarta and its surroundings have humid tropical climate that is very much influenced by the blowing Monsoon wind. The Monsoon season, being driven by the continental effect of Australia and Asia, splits the year into two main seasonal weather patterns: wet season (the East-Monsoon) and dry season (the West-Monsoon). 2 Characteristics of West Tarum Canal arrangement Many investigations have been carried out on the Citanun catchment (see e.g. Sriwana et al. [l] and Jatiluhur water resources management - Ministry of Public Works [4]). Nevertheless, many studies are still needed to cover the various complex issues in the catchment. In particular, the application of holistic (integrated) catchment management approach with its complex related issues (science/sociavengineering) is still lingering. Sustainable development of the catchment and conservation of water resources against extreme vulnerable situations and risk management should be central to the successful agenda of catchment management [S]. It is recognised that holism is the key element in managing such complex catchment effectively. However, this is not a straightforward process, particularly for this complex Citarum/Ciliwung/Tarum

3 River Basin Management 5!,: J h.-..! ', '.! '.- Ma (Ci Y ver ins). _ Ciliung..... Basin Figure 1: Schematic Layout of the West Tarum Canal Figure 2: Turbidity levels at the West Tarum Canal and crossing rivers during

4 6 River Basin Management Canal arrangement. The proposed integrated management approach has to evolve a set of processes and principles acceptable to stakeholders (i.e. all those with legitimate interest in the outcome) by which policy, strategy, and activities in general can be reviewed [6]. 2.1 Problems with Raw Water Supply Figure 1 shows the arrangement of the West Tarum Canal between the Ciliwung and Citarum basins. As can be seen, the most important rivers are the Citaruq Ciliwung, Cibeet, Clkarang, Bekasi, and Cisadane rivers. The Jatiluhur Reservoir is one of three reservoirs located in Citarum basin. It has a capacity of 0.9 X 10"m3 and surface area of about 83 X 109m2. The other two reservoirs are Saguling and Cirata Reservoirs. The Saguling Reservoir has a capacity of 2.75~10~ m3 with surface area with 53.4 x106 m'. With the exception of Jakarta, the Citarum basin has always been the most populated catchment in West Java. This obviously indicates that this catchment produces large quantities of waste as a consequence of the hgh degree of human activities, particularly industrial activities [2], [7]. These activities include textlle, clothing and footwear at the City of Bandung. As a result of such activities, the quality of water in the Saguling Reservoir has extremely been deteriorated. Moreover, industrial effluent is discharged to the Citarum River and to its tributaries without any treatment as a matter of course. The West Tarum Canal itself is a 70km man-made canal that was originally designed for irrigation and water supply purposes to the city of Jakarta and its surroundings. The Canal supplies raw water to both PAM Jakarta (16.1 m3/s) and to PAM Bekasi (0.133 m3/s) in addition to about 57,600 hectares of irrigation area at Kabupaten Kerawang and Bekasi. It is estimated that the West Tarum Canal supplies approximately 80% of Jakarta's raw water [4], [7]. The main source of water in the canal is the Jatiluhur Reservoir, whch receives, in turn, its water from the Citarum River. The Citarum River has an annual average flow of 180 m3/s, with dry season flow averages of 64 m3/s. Three main rivers intersect with the West Tamm Canal; these are the rivers Cibeet, Clkarang and, Bekasi Rivers. The upstream intake of the West Tanun Canal is the Curug weir, located at the intersection with the Citanun River (Figure 2). The flow rate in the West Tarum Canal reduces from about 80m3/s at the intake (Curug weir) to about 21 m3/s at the intake of the Buaran WTP at the eastern side of Jakarta. The flow is further reduced to 10 m3/s at Cawang, where it feeds back into the Ciliwung River. Deterioration of the water quality always exist along the Tamm Canal from point and diffused pollution sources in addition to high build-up of sediment. In order to ensure constant supply of water fiom the West Tarum Canal, several weirs across the Canal have been constructed, known by Bendung Tarurn Barat (BTB). A total of 53 BTB weirs have been constructed. One weir was built at the feeder from Cibeet River and other two weirs were located at the junction with the Bekasi Cikarang Rivers. In addition, there are 144 control structures across the West Tamm Canal (e.g. tunnels, siphons and aqueducts).

5 2.2 Water quality problems West Tarum Canal River Basin Management 7 Large catchment size, dense population and intensive agricultural and industrial activities, and lack of proper regulation and law enforcement, hghlight the increased the complexity associated with of the problems during raw water supply of reasonable quality for treatment purposes. The drainage area withm the West Tanun Canal suffers fiom water quality degradation caused by continual discharging of untreated waste. Quality of water from tributaries (i.e. fiom Cibeet, Cikarang and Bekasi) has systematically been deteriorated in the past few years. This has resulted in restricting the use of the canal's water for treatment during severe dry periods of the year. One of the crucial problems in the Canal is the high level of turbidity which tend to affect the water quality abstracted to the Buaran Treatment Works. Figure 3 shows the recorded turbidity in the West Tarn Canal (WTC) and the crossing rivers during the period , as recorded by the Ministry of Public Works and The Buaran Treatment Works. According to the guidelines of 1984 World Health Organisation (WHO) drinking water standards [8], the maximum turbidity level for drinlung water is 1.0 NW. With such high turbidity levels in WTC (> 500 NTU) acheving WHO guidelines becomes very difficult task. At present no definite conclusion may be drawn on the reasons that cause such high levels of turbidity. Detailed field monitoring programme on the Canal can defmitely answer such~questions. Additional cause for water quality deterioration in the west Tarum Canal is the presence of Igh levels of metals, malnly iron and manganese, at the intake of the Treatment Works. Previous studies conclude that local activities determine largely the most probable way of pollution sources. Industrialisation and urbanisation, together with intensified agricultural activities, lead to increasing water demands and at the same time, become the main sources for releasing contaminants [9]. In general, the potential sources of metals in the catchment can be one or more of the following [10]: (i) underlying geology, (ii) industrial disposal, (iii) agriculture practices, and (iv) water quality management in reservoirs. In general, the two possible pathways for the dispersion of manganese and iron compounds in the catchment are surface water and groundwater. These pathways are shown schematically in Figure 4. These two pathways differ in the-time and length scales associated with the transport of manganese and iron compounds. Following preliminary investigations, it was agreed that surface water is the most likely pathway of these chemicals. It should be mentioned that at this initial stage of the research project, the main attention is centred on surface water pathway. Contribution of groundwater to high concentration of manganese and iron compounds can be considered at a later stage depending on sound evidence based on field measurements. 3 Conceptual Modelling In this section, the development of a conceptual model for providing better understanding of the mechanisms involved in the transport processes of pollutant discharges of the West Tarum Canal is discussed. Because of the complicated

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7 River Basin Management 9 nature of the catchment and the lack of available information, the model would have to be developed in phases. h each phase, assigned set of objectives (or targets) would be clearly identified and linked into the overall aims of the model [2], [7]. Within the conceptual model, deterministic sub-models would be used for simulating the hydraulic and water quality processes in the complex pathways of the catchment [10], [13]. Therefore, concurrent field measurement programmes are imperative for the calibration and verification of these models. Until such measurements become available, the dynamic simulation of all hydraulic and water quality components of the system should be considered p rebary at this stage [7]. Proper calibration and verification of such models should follow in due course should reliable field data become available. 4 The system components Since the system lies between two basins connected through the West Tarum Canal with its crossing rivers, it has therefore been divided into two units. One unit represents the Citarum basin with Citarum River and the other unit represents the West Tanun Canal withm the Ciliwung catchment. Withm each unit, several sub-units interacting with each other may be added whenever necessary. Future studies will be required to determine the degree of interaction of the units and the sub-units within the system. The main elements of the suggested conceptual model are shown in Figure 5. As can be seen in the figure, the concept is basically to divide the catchment into zones or sub-catchment(s). The West Tarum Canal with its tributaries is defined hypothetically as one sub-catchment. This sub-catchment includes Citanun Catchment that is upper and middle Citarum, Cibeet Catchment, Cikarang Catchment and Bekasi Catchment. This assumption is considered because the Tarurn Canal, being a man-made canal, does not have natural catchment boundaries. As stated earlier, the deteriorating state of water quality in the Canal is a result of many uncontrolled and unrnonitored polluted (point and diffused) sources. For the purpose of applying the conceptual model, two sets of input data are assumed; the first and most difficult to quantify, is the effluent fed into the canal along its path, and the second is directly taken from the flow rates in the tributaries. 4.1 Hydrology information for sub-catchments At this stage of the conceptual model, river flow data in the sub-catchment (or sub-basins) is only used as a first approximation. lks is due to the fact that direct relationshp between rainfall and runoff distributions with flow hydrograph of the river was not determined. Recent investigations in the literature (Komuscu et al. [l l]) has applied the same hypothesis and found that no peak flows were observed with high rainfall intensities. In that study, the described approach was used since their main objectives were focusing on determining the critical levels in each sub-catchment, and not on carrying out in-depth time-dependent calculations that affect the catchment properties (e.g. activities, land use, hydrological and climate). Obviously, the hydrology characteristics of each subcatchment are core-input information in determining the water quality variations.

8 10 River Basin Management (Surface Runoff) 1 Vulnembilii and Defining Zones of Him Figure 4: Main components of the conceptual model

9 4.2 Water quality aspects in canal the sub-catchment River Basin Manc,ement 1 1 With the knowledge of the hydrological properties of the catchment and river hydraulics, the water quality aspects can be identified at any point (station) along the river network. Particular emphasis is placed on quantifying the dispersion characteristics from which zones of high and low concentration of various chemicals and metals, especially for iron and manganese can be identified [10], [13], [14]. From this, point and diffused sources of pollution can be identdied and further back-traced and correlated directly to the condition of water quality in the catchment. This procedure obviously requires detailed information on the various activities (domestic, industrial and agricultural) within each subcatchment. It is hoped that hs exercise is the first step towards full understanding of the various complex issues in the catchment and hence, towards realising sustainable management of water resources [6],[9]. As more detailed information become available in the future, locations of potential pollution sources will be further revealed. Detailed of such potential pollution sources should identify not only their location but also their type (e.g. industrial effluent, geochemistry). In general, the results should also address the inter-relationshp between the water quality aspects of the river and the hydraulic/hydrodynamic features that dnve flow motion and transport chemical discharges in the river network. 5 Conclusions The problems associated with water supply and quality criteria with the Citanun and Ciliwung basins are discussed. The study focused on the West Tarum Canal, a man-made canal that delivers water from the Citanun River to water treatment plant in Jakarta. The principal elements of a conceptual model was proposed for addressing the various complex mechanisms of water motion and also assessing the possible pathways of pollutant dispersion (with particular emphasis on metals such as iron and manganese) within the catchment. Detailed formulation of the deterministic models along with their calculation procedure and full-scale application to th~s case study will be reported in due course should sufficient information based on intensive field measurement programme. It is hoped that the implementation of the model should provide practical tool for testing the appropriateness of adopting different strategies for providing costeffective solutions to water resources management. 6 Acknowledgements The authors wish to thank Thames Water Research and Development, UK, for their financial sponsorship of the study. The authors wish also to acknowledge the support received from the Centre for Environmental & Water Engineering Research (FEWER), Civil Engineering Department, University of Indonesia. This study forms part of the first author's MSc dissertation, which has been

10 12 River Basin Management originated at the University of Surrey, UK. The views expressed in this paper are those of the authors and not of Thames Water plc. References Sriwana, T. et al. Volcanogenic pollution by acid water discharge along Ciwidey River, West Java (Indonesia). Geochemical Exploration, 62, pp. l61-182,1997. Ilchwan, M. Citarum catchment, West Java - Indonesia, development of a conceptual model for assessing the water resources and quality criteria using the river network model DESERT. MSc Dissertation, University of Surrey, UK, World Health Organization. Guidelines for drinking - water quality, 2nd ed., 1 and 2, Health Criteria and Other Supporting Information. pp , pp , Ministry of Public Works. Study and preparation of plan for raw water quality protection water supplied to treatment plants from Tarum Jaya and West Tarum Canal in Javaprovince. Internal Report, Clarke, K.F. Sustainability and the water environmental manager. CIWEM, 8, pp. 1-9, Gardiner, J.L. Sustainable development for river catchment. CIWEM, 8, pp , Fares, Y.R. & Ikhwan, M. Conceptual modelling for management of the CitarumICiliwung basins, Indonesia. Environmental Hydrology, 9(10), pp. 1-13,2001. World Health Organization. Manganese, Environmental Health Criteria, No. 17, Holt, M.S. Source of chemical contaminants and routes into the freshwater environment. Food and Chemical Toxicology, 38, pp ,2000. [l01 Alexander, N. et al. A case study of longitudinal dispersion in small lowland rivers. Water Environment Research, 69(7), pp , [l11 Komuscu, A.U.& Legates, D.R. Effect of rainfall variability on spatial accumulation of peak runoff and excess runoff depth: Little Washita river basin, Oklahoma. Environmental Hydrology, 7(6), pp. 1-25, [l21 Zaw, M., Chiswell, B. Iron and manganese dynamics in lake water. Water Resources, 33, pp , [l31 Legret, M. et al. Simulation of heavy metals pollution from stormwater infiltration through a porous pavement with reservoir structure. Water Science Technology, 2, pp , [l41 Duke, M. Geological sources of metals in the environment. Reports of the International Workshop on Risk assessment of Metals and their Inorganic Compounds, Ottawa, pp , 1996.