Scholarly article on topic 'Urban Lakes in Megacity Jakarta: Risk and Management Plan for Future Sustainability'

Urban Lakes in Megacity Jakarta: Risk and Management Plan for Future Sustainability Academic research paper on "Earth and related environmental sciences"

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Abstract of research paper on Earth and related environmental sciences, author of scientific article — Cynthia Henny, Ami A. Meutia

Abstract The impact of urban development in the distinct surrounding inhabited areas on urban lakes in megacity Jakarta has been so pervasive that makes the lakes very vulnerable to environmental disturbances. High levels of disturbances to the urban lakes from urban development in the past and recent years, such as lake filling, land use change, shoreline encroachment, and garbage dump, have caused nearly 10 - 20% of urban lakes loss in megacity Jakarta. The consistency of lakes loss has been estimated from the old-Dutch map to the recent year maps indicating that the lakes continuously have been sacrificed for urban area development. In addition to the lake front destruction, siltation and the excessive macrophyte coverage have caused more than 25% of existing lakes shrinkage in area and volume and based on the lake morphology assessment, nearly 50% of lakes have been damaged. The lakes inurban village, rural village, agricultural and urban village – industrial areas are at high risk of lakefront landscape destruction, siltation/sedimentation, eutrophication and water pollution, including pathogenic bacteria and toxic pollutants contamination that can pose threat on human's health as results of untreated sewage inflow and storm water runoff to the lakes. The complexity of the problems faced by urban lakes in Jakarta requires a comprehensive management plan that is not only effective in maintaining the stability of lake ecosystem but also effective in improving urban life, such as socio-culture-economic conditions of people around the lakes. Fundamental requirement is that the urban lake should be managed according to its surrounding characteristics and conditions, and functional context.

Academic research paper on topic "Urban Lakes in Megacity Jakarta: Risk and Management Plan for Future Sustainability"

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Procedía Environmental Sciences 20 (2014) 737 - 746

The 4thInternational Conference on Sustainable Future for Human Security, SustaiN 2013

Urban Lakes in Megacity Jakarta: Risk and Management Plan for

Future Sustainability

Cynthia Hennya* and Ami A. Meutiab

aResearch Center for Limnology-Indonesian Institute of Sciences (LIPI), Cibinong Science Center, Cibinong16911, Indonesia bResearch Institute for Humanity and Nature (RIHN), 457-4 Motoyama, Kamigamo, Kita-ku, Kyoto 603-8047, Japan

Abstract

The impact of urban development in the distinct surrounding inhabited areas on urban lakes in megacity Jakarta has been so pervasive that makes the lakes very vulnerable to environmental disturbances. High levels of disturbances to the urban lakes from urban development in the past and recent years, such as lake filling, land use change, shoreline encroachment, and garbage dump, have caused nearly 10 - 20% of urban lakes loss in megacity Jakarta. The consistency of lakes loss has been estimated from the old-Dutch map to the recent year maps indicating that the lakes continuously have been sacrificed for urban area development. In addition to the lake front destruction, siltation and the excessive macrophyte coverage have caused more than 25% of existing lakes shrinkage in area and volume and based on the lake morphology assessment, nearly 50% of lakes have been damaged. The lakes inurban village, rural village, agricultural and urban village - industrial areas are at high risk of lakefront landscape destruction, siltation/sedimentation, eutrophication and water pollution, including pathogenic bacteria and toxic pollutants contamination that can pose threat on human's health as results of untreated sewage inflow and storm water runoff to the lakes. The complexity of the problems faced by urban lakes in Jakarta requires a comprehensive management plan that is not only effective in maintaining the stability of lake ecosystem but also effective in improving urban life, such as socio-culture-economic conditions of people around the lakes. Fundamental requirement is that the urban lake should be managed according to its surrounding characteristics and conditions, and functional context.

© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/3.0/).

Selectionandpeer-reviewunder responsibility of the SustaiN conference committee and supported by Kyoto University; (RISH), (OPIR), (GCOE-ARS)and(GSS)asco-hosts

Keywords: urban lakes; megacity; water quality; management plans

* Corresponding author. Tel.: +6221-875-7071; fax: +6221-875-7076. E-mail address: cynthia_azis@yahoo.com

1878-0296 © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Selection and peer-review under responsibility of the SustaiN conference committee and supported by Kyoto University; (RISH), (OPIR),

(GCOE-ARS) and (GSS) as co-hosts

doi:10.1016/j.proenv.2014.03.088

Keywords: urban lakes; megacity; water quality; management plans

1. Introduction

The lakes in urban megacity Jakarta, called as "setu or situ" by the local people, are part of the watershed area of two main rivers, i.e. Ciliwung and Cisadane Rivers that flow across the interconnected regions within the megacity. Urban lake management has been the key point of the watershed management plan of those two rivers to minimize the impact of flash flooding coming from the upstream region and to overcome the water crisis in downstream of megacity Jakarta [1].Besides maintaining the surface and ground water balance, the urban lakes are also important in maintaining the urban ecosystem [2]. In addition to its major function as flood control and water supply, the lakes can also be managed as recreational, educational, fishing and even for economic purposes. Hence, the existence of urban lakes can contribute to increase the quality of life in urban centers by increasing the amenity of urban environment.

According to Schuler and Simpson, for the purposes of watershed management, the urban lakes are distinct than common natural lakes. The lakes tend to be small and shallow with a large watershed area that contains more impervious cover, such as pavement, roads and buildings and often lack of substantial vegetation cover which exert strong influence to the lake [3]. Although some lakes share this common type of urban watershed, the urban lakes in megacity have other distinct types of watershed. The urban lakes in megacity Jakarta can have mixed urban and other types of watershed, such as rural, industrial and even agricultural area. The impact of urban development in these distinct surrounding inhabited areas on urban lakes in megacity Jakarta have been so pervasive that makes the lakes very vulnerable to environmental disturbances. Land expansion is needed for housing as a result of urban development which has caused extensive lake shoreline development even reaching to the water bodies that causes serious damage to urban lakes and even disappearance of lakes due to land use change. Lakes are often used as a dumping place for garbage and collecting untreated sewer and storm water runoff. Moreover, lack of concern of the public and lack of management of the government have aggravated the damage of environmental conditions of urban lakes. Limited previous studies have reported on several urban lakes conditions in megacity Jakarta, including area shrinkage, siltation/sedimentation, eutrophication and water pollution [4,5,6]. Some lakes are reported to have been contaminated with toxic cyanobacteria and metals contamination [6,7,8]. Lake shrinkage and eutrophication or pollution problems are common in urban lakes problems found in other countries as well; however, no extensive lakes loss case reported happened, unlike the one in megacity Jakarta [2, 3, 9, 10].

Downstream area of megacity Jakarta has been facing chronic problems of severe flash floods annually from the upstream region during the wet season. In addition, the exploitation of groundwater usage and polluted surface water has caused shortage of clean water during the dry season. The lakes in urban megacity Jakarta have lost their capacity to support their function as flood control, water supply, and for other direct human uses. The negative impacts of urban water related issues can be minimized by optimizing the function of urban lakes as an impounding for local storm water runoff to control flood, to recharge and to maintain groundwater table, and to reserve in dry seasons. It is quite unfortunate that despite its pivotal role in maintaining urban water and urban ecosystem, lakes in the urban areas have received little attention.

This paper was aimed to examine the loss, shrinkage in area and environmental conditions of urban lakes according to the type of surrounding inhabited area in megacity Jakarta. It determined the risk as results of the impacts of distinct urban development to the lakes and develops management plan based on the ecosystem approach for their future sustainability according to the types of lake surrounding inhabited area in urban ecosystem and functional context. The ecosystem approach in urban lake management is a strategy for the integrated management of lake's catchment area, water body and biodiversity of flora fauna in and around the lakes and human that promotes conservation and sustainable use in an equitable way. The management involves all user groups in comprehensive management. Management on functional context is a management based on the function of the lakes according to lake's condition and socio-economic benefit to the people around the lakes.

Fig. 1. Location and the regions of megacity Jakarta (a) Indonesian map by Google Map, 2103; (b)Jabodetabek map originated from Mimura

(RIHN project researcher, 2013).

2. Research Method

2.1. Urban Lakes Ste in Megacity Jakarta

The urban lakes examined were in the area of megacity Jakarta which is basically the capital city of Jakarta and surrounding regions. The surrounding regions included Regency and City of Tangerang, and City of South Tangerang which is in the Province of Banten, and City of Depok, Regency and City of Bogor, and Regency and City of Bekasi which are in the Province of West Java. The area of megacity Jakarta is known as Jabodetabek which can be seen in Fig. 1. Bogor regions are in the upstream area, Depok is in the middle area, and Tangerang, Bekasi and the capital city of Jakarta regions are in the downstream area of two main rivers i.e. Ciliwung and Cisadane Rivers. The map of the urban lakes distribution in megacity Jakarta can be seen in Fig. 2. The map was digitized with the help of Mimura and Uchiyama (RIHN project researchers, 2013) based on the SRTM and 2006 BAKOSURTANAL map according to the area elevation and the watershed boundary of several rivers. The existence of most lakes in the megacity Jakarta area is in the elevation of 21-100 m above sea level (asl), indicating that the lakes obviously might be functioned as water impoundment to reduce the impact of flash floods coming from the upstream area.

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2. The maps of urban lakes distribution in megacity Jakarta.

2.2. Estimation of Lakes Quantity

The estimation of quantity of lakes and lakes loss was determined using several maps from the past colonial time to the current one with Google Earth Digital Globe map as a base map, and using a database obtained from an associated government agency (BBWS-CC) (Table 1). The estimation of the lakes and the lakes loss quantity was done by overlaying the topographic map with Google Earth map or by checking each lake spotted in the examining map with Google Earth Map according to its coordinate. The reservoirs which are mostly in the capital city of Jakarta were not included as the urban lakes in this study. The lakes estimated in this study were the lakes within the area of at least > 0.5 ha. The lake area shrinkage was determined only based on the database obtained from BBWS-CC.

It is necessary to point out that some of the maps, such as 1990 map, the city maps of 1997/1998 and 2009, do not cover the whole area of megacity Jakarta and the database of lakes collected from BBWS does not include the whole existing lakes, especially the new lakes from post sand mining. As seen in the lake distribution map (Fig. 2) and in the 2007 map used for lakes quantity estimation, many new lakes were spotted - presumably of being developed from post sand mining. These new lakes have not been spotted in the older maps or even in the 1990 map. The previous study also reported that there were more urban lakes spotted in megacity Jakarta area in 2000 lands at map when compared to Dutch map of 1922-1940 [11]. Pit lakes from the post sand mining have become potential urban lakes;however, they are not included in BBWS-CC database. The estimation of new lakes in the 2007 map was considered one if the lakes are in one area and interconnected to each other or very close to each other. Therefore, each map observed should give varied total number lakes spotted. The purpose of the calculation of lake quantity from the older maps to the recent ones was mainly to determine the trend of the lake loss quantity in each time, not to show the historical changes of lake loss.

Table 1. Maps and database sources.

Map and database Year Scale Publisher Source

Google Earth - Digital Globe © 2013 Google

Java 1915-1942 1:50,000 Batavia Topographische Dienst (Dutch map) RIHN*

Indonesia ca.1954 1:250,000 US Army Map Service RIHN

Soviet Military Map ca.1958 1:54,000 Soviet Military TopoMapper by ATLOGIS

Peta Rupa Bumi Indonesia ca.1990 1:25,000 BAKOSURTANAL RIHN

Jakarta-Jabotabek - City map 1997/1998 1:15,000 Gunter W. Holtorf RIHN

Peta Struktur dan Pola Ruang - Badan Koordinasi Tata Ruang Nasional ca.2007 1:150,000 BAKOSURTANAL RIHN

Megapolitan: Map & Street Guide by Dr. Riadika Mastra 2009-2010 1:10,000 PT Bhuana Ilmu Populer RIHN

Lake Database - Jabodetabek 2007/2011 BBWS-CC BBWS-CC**

* Y. Mimura, Y. Uchiyama - Project Researchers, Research Institute for Humanity and Nature (RIHN), ** Ministry of Public Work Agency for Region of Ciliwung-Cisadane Rivers

2.3. Environmental Condition of Lakes

The environmental conditions of lakes were examined based on several lake surrounding area characteristics of urban ecosystem which might have big influence to the lakes conditionswithin the radius of 500 musing Google Earth image. There were 8 types of urban ecosystem observed in the surrounding lake area in which the first four were adopted from other megacity study by Hayashi [12] and the latter four were additional (Fig. 3, Table 2). The risk levelsof lake environmental conditions were determined using the data from eight lakes collected as part of this research in addition to the database obtained from associated government agencies. The list of the lake data sources is presented in Table 3.

Rui.il -I 'i b.mIRnbau) Village Aica<E) IiidiMi lal Area < F)

Fig. 3. Image of the types of surrounding inhabited area of urban lake ecosystem in megacity Jakarta (Google Earth images). Table 2. Characteristics of the lake surrounding inhabited area in megacity Jakarta

Map and database

Characteristics

Urban Village Area (A) Planned Residential Area (B) High-Rise Residential Area (C) Rural Village Area (D)

Industrial Area (F) Industrial-Urban Village Area (G) Agricultural Area (H)

Irregular and more dense housing, no proper road, narrow alley access

Regular housing, proper road access, usually developed by Estate

Tall buildings, usually office and apartment buildings

Less dense housing mixed with agricultural area

Rural-Urban (Ruban) Village Area (E) At least half of the area is rural type and the other half is urban village

residential area type

Factory buildings

Half area is industrial and the other half is residential area More than 50% of surrounding area is agricultural area

Table 3. The sources of database for urban lake environmental conditions

The source of data Number of lakes The type of data

BBWS-CC (2011)* 168 Physical conditions (lakes area, volume and

shoreline conditions)

PSDA (Center for Water Resources in Bogor) 137 Physical conditions (shoreline condition, siltation,

(2010-2011) macrophyte coverage, water body condition)

BPLH the Capital City of Jakarta (Environmental 15 Physical conditions (percentage of macrophyte

Management Agency) (2008-2012) coverage) and water quality (physical and chemical

parameters)

BLH Depok (Environmental Management 20 Physical conditions(, siltation/sedimentation,

Agency)(2006, 2009, 2011) percentage of macrophyte coverage and water

quality

BPPD Bekasi Regency (Regional Planning and 14 Physical conditions (shoreline condition, siltation,

Development Agency) (2010) macrophyte coverage, water body condition)

Public Work Agency - Tangerang City (20100 6 Physical conditions (shoreline condition, siltation,

macrophyte coverage, water body condition)

Highway and Water Resources Agency- Bogor 6 Physical conditions (shoreline condition, siltation,

City (2012) macrophyte coverage, water body condition)

Research data collection (2013) 8 Physical conditions of lake and water quality

(physical and chemical parameters)

* Lakes observed from other agencies including in this study data collection are also the lakes included in the data list of BBWS-CC.

The eight lakes representing eachlake surrounding area characteristics were observed and sampled for water quality measurements. The water quality measured included pH, temperature, turbidity, Dissolved Oxygen (DO), Total Suspended Solids (TSS), Chemical Oxygen Demand (COD), Ammonia, Nitrate and phosphate concentrations. Water sampling and water quality parameters analyses were done according to Standard Methods procedures [13]. Several lakes data from associated government agencies included faecal coli bacteria and toxic metal concentrations. Fourtypes of risk categories of lake environmental conditions examinedwere lake front area destruction/shoreline encroachment, siltation/sedimentation, eutrophication (excessive macrophyte coverage or algal bloom), and water pollution using scoring index i.e. score 1 (high risk); score 2 (moderate risk) and score 3 (low risk). The risk assessment of lake environmental condition was done by using the water standard and modified valuation criteria of lake status issued by the Environmental Ministry of Indonesia [14] (Table 4). The level risk of each lake condition for each type of lake surrounding inhibited area was high when the number of lakes exposed to the conditions were > 25%; moderate when the number of lakes exposed to the condition were 5 - <25% ; and low when the lakes exposed to the condition were < 5%.

Table 4. Risk assessment for urban lake environmental conditions

Indicator Parameter Parameter conditions Value

Shoreline encroachment Shrinkage in area in 4 years >25% 1 (High)

(green zone buffer) 5 - 25% 2 (Moderate)

< 5% 3 (Low)

Vegetation coverage in 0 - 5m 1

shoreline <50 m 2

50 - 100 m 3

Siltation/Sedimentation Reduction of depth in 4 years > 1 m 1

0.5 - 1 m 2

<0.5 m 3

Eutrophication/macrophyte % macrophyte coverage >25% 1

coverage 5 - 25% 2

< 5% 3

Dark green with green scum 1

Water Color Light green no scum 2

Clear/light yellowish 3

Water quality Organic concentration Class IV 1

(as COD), nutrient (N/P), Class III 2

Coliform, Toxic metals Class I/II 3

3. Results and Discussion

3.1. The Existence of Lakes

The number of lakes spotted in each map quite varied with a very high number of lakes spotted in the 2007 map. It is quite perceptible that there were some lakes losses; but there were some lakes developed which were obviously man-made lakes. The data presented in Fig. 4a indicated that there was quite consistent number of lakes losses spotted from the old-Dutch map or the recent one when overlaid with Google Earth map and from the actual database of BBWS-CC. The results indicated that the lakes had been continuously sacrificed for urban development. The disappearance of lakes was probably due to shoreline development, lake filling and land use change that are developed for infrastructure, residential area, farming or even divided as fish ponds.

The most lakes losses reported or spotted were in the very dense urban village area and in the rural or agricultural area which were developed into residential area. The most lake loss cases occurred in the rural area and agricultural area where the lakes were quite invisible and usually not well managed.

Most of lakes had area of under 5 - 10 ha, and only quite few number of lakes with area of > 25 ha (Fig. 4b). However, the lakes with area > 25 ha underwent the area reduction the most. Calculated from BBWS-CC data, the reduction of lake area has occurred for several lakes in 4 years (Fig. 5a).

* N1: Not identified

Fig. 4. (a) Profile of urban lakes existence over year courses in megacity Jakarta; (b) Profile of urban lakes according to its area

Although the number of lakes with the area reduced > 50 % was only about 5 %, the number of lakes with area reduced < 50 % was quite significant percentage and the area reduced was about 10 - 30%.The lakes with significant change of area also suffered from siltation/sedimentation. These lakes are in the verge of disappearance and will likely undergo the land use change if they are not restored. The cases of lake's area reduction were mostly due to the pressure of the urban development, such as land use change on the lake's periphery, shoreline encroachment, sedimentation and excessive macrophyte coverage in the littoral lake zone. Based on the morphology of lakes data, such as lakefront landscape destruction, the existence of green buffer zone, shoreline encroachment, siltation and percentage of macrophyte coverage, close to half of existing lakes were damaged (Fig. 5b). Most of lakes with area reduced and degraded conditions were in the urban village, rural village, rural-urban village, urban village-industrial and agricultural areas. The lakes in the planned residential, high-rise residential and industrial areas which have good management program with the lake front area protection, the case of shoreline encroachment or significant area change will not occur. The lakes are usually managed well for recreational area and/or for other purposes which increase the amenity of urban ecosystem.

The fast growing population and the land needed for housing have led to land expansion from the capital city of Jakarta to the outskirt and suburb areas. Other megacity study showed how the increase in population has led the urban area expansion from the only limited in the central of capital city of Jakarta in 1930 of Dutch period to the whole area of megacity Jakarta in 2006. The study also indicated that 50% of land cover in the urban capital city of Jakarta was the residential area [12].Most of existing urban lakes in megacity Jakarta are in the rural, agricultural and urban village areas (Fig. 6). It is indicated that ongoing urban development for residential areas will likely to cause the expansion of the urban areas to the rural and agricultural areas.

* NI: Not identified

Fig. 5. (a) Existing urban lakes conditions based on the area shrinkage; (b)Lake morphological conditions

Fig. 6. Distribution of lakes according to surrounding lake urban area in megacity Jakarta

Several cases found where the lakes with very large area in the rural and agricultural areas have been sacrificed for residential area development and infrastructure. The urban lakes in the rural and agricultural areas will be likely sacrificed for the residential area in the future if they are not included in the urban planning as part of urban landscape feature that has very important function as water resources that can contribute to increase the quality urban life.

3.2. Risk Level of Environmental Conditions

The risk level showed how the lakes as part of urban ecosystem responded to the stress resulted from the urbanization of the surrounding area. Table 5 presents the level of risk of lake's environmental conditions based on the surrounding inhabited area characteristics of urban ecosystem.

Table 5. Level of risk of lake's environmental conditions based on the characteristics of surrounding inhabited area

Type of condition Type of lake surrounding inhabited area*

A B C D E F G H

Lakefront landscape destruction/ High Low Low High High Moderate High High

shoreline encroachment

Siltation/sedimentation High Moderate Moderate High High Moderate High High

Macrophyte invasion/Algal High Low to Low to High High Moderate High High

bloom Eutrophication Moderate Moderate to High

Water pollution High Low to Low to Moderate High High High Moderate

Moderate Moderate to High to High

Note: * (A=Urban village area; B=Planned residential area; C=High-rise residential area; D=Rural village area; E=(Rural-Urban) "Ruban" village area; F=Industrial area; G=Urban Village-Industrial area; H=Agriculturalarea)

The lakes database showed that most of lakes in the urban village, rural village, rural-urban village, urban-industrial and agricultural types of inhabited urban area were at high risk in all categories of environmental conditions. The lakes had no or less green open space, became narrow and shallow, and the water was greener -indicatingthe eutrophication of algal bloom -and part of the surface water or entire surface water were covered by floating excessive macrophytes, such as Eichorniasp. Eutrophication of lakes is one of the most public concern due to its severe impacts, such as the presence of nuisance and toxic cyanobacteria and depletion of dissolved oxygen that can cause fish killed. Cyanobacteria has been found to be dominating in the lakes surrounded by urban village, rural village and agricultural area [5]. The lakes in agricultural, urban village and rural village surrounding areas had much highly risk to the eutrophication problem due to high phosphor loadings. Major inputs of phosphor in urban lakes are usually from agriculture and urban activities [15].

The urban lake water in megacity Jakarta was mostly polluted by nutrient, organic material and even toxic pollutant and bacterial contamination. Even for the lakes in the planned residential or high rise residential areas provided with sewer treatment system where the lakes were well managed, there were usually still at risks of

siltation and nutrient pollution due to storm water runoff. The lakes in the urban village, rural-urban village, industrial and urban village-industrial types of urban ecosystem are usually at high risk of toxic pollutant, especially if the industry is not provided with water treatment facility. Although the water was still in the limit of water quality standard, the metals concentration of Hg, Cd, As and Pb in the sediment of several lakes in the urban village, rural village and industrial area were found above the effect range low (ERL) and the sediments were classified toxic [7]. Cd and Pb were also found in quite high concentrations in the phytoplankton for some of the lakes in those inhabited types of urban ecosystem [6]. These conditions could potentially pose health threat to human beings, especially for the lakes used for fishery or fishing activity.

3.3. Management Plans

Ineffective management due to the lack of knowledge on each lake ecosystem has caused the lakes in megacity Jakarta not functioning well as either flood control, water supply and/or for other direct human uses. Proper management plan for future lake sustainability should be based on ecosystem approach that takes into account not only in maintaining the stability of hydrological regime but also in maintaining the stability of lake's ecosystem to support the biogeochemical processes, biodiversity and promote socio-economic benefit to the people around the lakes. This includes the management of lake's watershed which covers the lake front area, the wetland/littoral zone and the water body. Properly managed urban lake should have green open space in the lake front landscape, good water quality, and maintain wetlands for habitat and feeding ground of aquatic fauna to support the biodiversity. Proposed common management plans for urban lakes include preservation of lake front area and create green belt to the lake and wetland area to maintain biodiversity of lakes, control storm water runoff and divert sewage channel and provide with sewage and storm water treatment plants to reduce sedimentation, nutrient and other toxic pollutants and bacterial contamination [3,16]. Other possible remediesinclude sediment dredging, creating flushing system and on-site treatment system, such as by using constructed and floating wetland treatments. Proper management plans according to lake function can be seen in Table 6. The lakes without lake front area to build buffer zone, even to create green open space and/or wetland/littoral zone, can still be managed by creating the constructed floating wetland and creating the feeding ground or micro habitat by using natural product materials to build the retaining wall. Sewage and storm water runoff treatment facility must be provided for the lakes to be functioned for direct human use. The lakes in industrial area must not be used for any direct human use.

Table 6. Management plan for function context in different surrounding inhabited area of urban ecosystem

Function Context Type of surrounding inhabited area*

A, D,E,H B,C F,G Plan

Flood control, water V V V Maintain the capacity of the lakes by deepening the lake; interconnect

supply, ground water the lakes with channel, provide with sluices

recharge (GWR) V

Drinking water source x x Only for less polluted lakes and maintain with good water quality

standard for drinking water source

Fishing, recreational, V V x Lakes should have very minimized of bacterial coli form counts, no

social ,culture and toxic cyanobacteria and below limit of toxic pollutant concentrations.

economic purposes Provide amenity, and maintain part of wetland in lake beach area.

Irrigation V x x Lakes should have below limit of toxic pollutant concentration.

Note: * (A=Urban village area; B=Planned residential area; C=High-rise residential area; D=Rural village area; E=(Rural-Urban) "Ruban" village area; F=Industrial area; G=Urban Village-Industrial area; H=Agriculturalarea); (V = suitable; x = unacceptable)

The management of urban lakes in megacity Jakarta requires integrated management which involves governments, private sectors and public. Successful integration of lake management system requires good governance as well as good policies and good management program. Since each urban lake has specific problems and purposes, the management plan should be developed for each urban lake. Wrong practice of management program, such as building retaining concrete wall in all lake periphery and not maintaining part of wetlands, should not be done, unless for the lakes that are at higher risk of shoreline erosion, because it can cause dysfunctional in lake's ecosystem and biodiversity loss. Activity of floating cage fishery, which is observed in several urban lakes of megacity Jakarta, should not be acceptable due to addition of organic and nutrient loading to the lakes that can

aggravate the eutrophication problem to the lakes and due to hygiene concern for human's health. Therefore, good and proper management plan should also incorporate provision of scientific findings related to the hydrological and ecological issues. The succeeded plan should increase water quality and create the aesthetic of the lake to maintain biodiversity to provide healthy urban life and offer social, culture, and economic benefits especially for the lakes in the residential areas.

Conclusion

Urban lakes in megacity Jakarta have been sacrificed and encroached continuously as land for housing, industry, transportation and farming. Lakes have been disappearingand reduced in area and depth. Overall, the conditions of existing urban lakes in megacity Jakarta physically and ecologically have been degraded due to lake front landscape destruction, siltation, macrophyte coverage and water quality deterioration. The lakes in urban village, rural village, and agricultural areas types of urban ecosystem are at high risksof being more degraded and even disappeared in the future if they are not properly managed. The complexity of the problems faced by urban lakes in megacity Jakarta requires a comprehensive management plan that should not only be effective in maintaining the stability of the ecosystem of the lake across interconnected regions which increases the lake potential, but also effective in improving socio-culture-economic conditions around the lakes. Since each urban lake has unique levels of risks due to different impacts from urban development, therefore, specific management plan should be developed for each urban lake.

Acknowledgement

The research is part of Megacity Project lead by Shin Muramatsu and funded by Research Institute of Humanity and Nature (RIHN), Kyoto, Japan. The authors would like to thank Yutaka Mimura and Yuta Uchiyama who have provided most of the maps used in this study and the associated Indonesian Government Agencies who have provided thelake data.

References

1. Sakethi M. Why Jakarta flooding: Flood mitigation of the capital city Province of Jakarta. PT Mirah Sakethi. Jakarta; 2010.

2. Snehal P, Unnati P. Challenges faced and solutions towards conservation of ecology of urban lakes. International Journal of Scientific & Engineering Research. 2012;(10):170-183.

3. Schuler T, Simpson J. Introduction: Why urban lakes are different. Urban Lake Management. Watershed Protection Techniques 2001; 3(4): 747-750.

4. Rosnila. Land use change and its effect on the lake's existence: Case study of Depok city. Master Thesis. IPB. Bogor;2004.

5. Hendrawan D. Water quality of rivers and lakes in the capital city of Jakarta. MAKARA TEKNOLOGI2005; 9(1); 13-19.

6. Prihantini NB, Wardhana W, Hendrayanti, Widyawan A, Aryani Y, Rianto R. Biodiversity of cyanobacteria at several lakes in Jakarta, Depok and Bogor. MAKARA SAINS 2008; 2(1): 44-54.

7. Satya A, Bakri R, Hartoto DI, Chrismada T, Sulawesty F. Assessment of lead and cadmium bioaccumulation level in phytoplankton at several shallow lakes of Bogor Regency, Indonesia. International Symposium on Southeast Asian Water Environment2011;9: p105-112.

8. Suryono T, Sudarso Y, Pratama GY, Yuniarti I, Rosidah. Concept development of Screening Level Concentration (SLC) as a guideline for sediment quality: Case study of shallow lakes in West Java. Research Center for Limnology; 2011.

9. Wu J, Xie H. Research on characteristics of changes of lakes in Wuhan's main urban area. Procedia Engineering. 2011; 21: 395-404.

10. Islam MN, Kitazawa D, Runfola DM, Giner NM. Urban lakes in developing nation: Drivers, states, and impacts of water quality and quantity in Dhaka Bangladesh. Lakes and Reservoirs: Research and Management 2012; 17: 253-263.

11. Roemantyo, Noerdjito M, Prabandini D, Maryanto I. Changing in lake number in Jabodetabek in the year of 1922-1943 and 2000. In: Ubaidillah R,, Maryanto I, Amir M, Noerdjito M, Prasetyo EB, Polosakan R, editors. Management of Bioregional in Jabodetabek: Challenges and Solutions; 2003,p. 85-99.

12. Hayashi K. Characteristics of living environment of tropical Asian megacities - Case of Jakarta metropolitan area. In Okabe A. Asian Tropical Megacities. Japan Center for Area Development Research2013;581: p 27-32.

13. APHA/AWWA/WEF. 2005. Standard Methods: for the examination of water and wastewater. 21st Edition.

14. Environmental Ministry of Indonesia. Strategy of shallow lake conservation in Jabodetabek, 2007: p63.

15. Egemosa S, Jensen HS. Phosphorus form in urban and agriculture run off: Implications for Lake Nordborg. Lake and Reservoir Management2009; 25:410- 418.

16. Birch S, McCaskie J. Shallow urban lakes: a challenge for lake management. Hydrobiologia 1999; 395/396: 365-377.