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Assessing the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia --Manuscript Draft--

Manuscript Number: GSD_2020_395R1 Article Type: Research Paper Keywords: system dynamics; water demand; groundwater conservation.; groundwater balance; groundwater availability Corresponding Author: Erna Savitri University of Indonesia Jakarta, Jakarta Capital Special Region INDONESIA First Author: Erna Savitri Order of Authors: Erna Savitri Djoko M Hartono Tri Edhi Budhi Soesilo Setyo Moersidik Abstract: The purpose of this groundwater balance study is to see whether the status of the carrying capacity of the study area is a water surplus area or a water deficit area. The study area in this research is residential in (1) Kemayoran District, Central Jakarta with a damaged zone category, (2) Jagakarsa District, South Jakarta with a safe zone category. Therefore, this groundwater balance research focuses on developing dynamic system modeling as a feedback approach. In this research, the feedback approach is carried out based on the community water needs subsystem, land conversion subsystem, and groundwater availability subsystem. The model simulation is carrying out to predict the 2020-2080 subsystem relationship. Based on the results of the analysis, it shows that before 2069 the two areas a water surplus areas with the medium critical category. However, in 2070 onwards, groundwater availability in the region begins to decline and experiences a water deficit in a very severe level. As a prevention of groundwater imbalance in residential areas, the research results obtained several strategies for implementing groundwater conservation policies, namely (1) reducing the level of community dependence on groundwater, (2) increasing water conservation areas, (3) reducing the level of groundwater pollution, (4) decrease activities that have an impact on land-use change. Suggested Reviewers: Prosun Bhattacharya [email protected] Barbara Tomaszewska [email protected] Dinesh Mohan [email protected] Opposed Reviewers: Response to Reviewers:

Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation That this article is the authors' original work, has never been published prior publication, and isn't under consideration for

Jakarta (Indonesia), 1 Juli 2020

To: Editors of Groundwater for Sustainable Development

Dear Editors,

We wish to submit an original research article entitled “Assessment the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia” for consideration by "Groundwater for Sustainable Development”.

We confirm that this article is the authors' original work, has never been published prior publication, and isn't under consideration for publication elsewhere.

In this paper, we show that population problems in Jakarta are one of the inhibiting factors in efforts to improve the quality of the physical environment, thereby causing a socio-environmental impact on groundwater imbalance. This research focuses on developing dynamics system modeling using groundwater balance variables. This study aims to assess the sustainability of groundwater balance to simulate groundwater conservation policies in residential areas. The results of the study state that to apply an area's groundwater conservation policy, it is necessary to assess groundwater balance first.

The authors of the paper are: Erna Savitri, Djoko M. Hartono, Tri Edhi Budhi Soesilo, Setyo S. Moersidik

We believe that this manuscript is appropriate for publication in "Groundwater for Sustainable Development".

We have no conflicts of interest to disclose.

Please address all correspondence concerning this manuscript to me at [email protected]

Thank you for your consideration of this manuscript.

Sincerely,

Erna Savitri Indonesian School of Environmental Sciences, Jakarta, Indonesia Jalan Salemba Raya No.4, Jakarta Pusat, DKI Jakarta, Indonesia (10430) Corresponding Author (Email: [email protected]). Phone: (+62) 085216247958

Cover Letter

Jakarta (Indonesia), January 22, 2021

Manuscript Number: GSD_2020_395

Tittle: Assessing the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia

To: Editors of Groundwater for Sustainable Development

Dear Editor in-chief Mr. Professor Prosun Bhattacharya

Thank you very much for the opportunity to submit our revised manuscript. We appreciate the Reviewers' comments which we find to be constructive and delivered in the most professional and appropriate manner. We have addressed all the comments which are now reflected within our revised manuscript.

We attached the following files: 1. Revised manuscript 2. Responses to the Reviewers' comments

The first author has repeatedly checked the instructions within the ‘Guidance for Authors’ so that our manuscript complies with the Journal’s style and other requirements.

Thank you very much for the opportunity to consider our revised manuscript, and we look forward to hearing from you.

Sincerely,

Response to Reviewers

Jakarta (Indonesia), January 22, 2021

Manuscript Number: GSD_2020_395

Tittle: Assessing the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia

To: Editors of Groundwater for Sustainable Development

Dear Editor in-chief Mr. Professor Prosun Bhattacharya

Thank you very much for the opportunity to submit our revised manuscript. We appreciate the Editor and Reviewer comments which we find to be constructive and delivered in the most professional and appropriate manner. We have addressed all the comments which are now reflected within our revised manuscript.

The first author has repeatedly checked the instructions within the ‘Guidance for Authors’ so that our manuscript complies with the Journal’s style and other requirements.

Detailed responses to the Editor and Reviewers' comments are outlined below.

Comment 1: The language and grammar of the entire manuscript need to be improved significantly for clarity, coherence, and easy understanding.

Thank you. We have made major revisions to the text’s entire language and grammar in this Manuscript to make it as clear, coherent, and understandable as is suggested.

Comment 2: The title needs to be checked; in its current form, the first word should be Assessing and not Assessment.

Thank you. We agree to change the article's title by using the first word is Assessing, as suggested. For this reason, the title of our article is "Assessing the sustainability of the groundwater balance using a dynamic system modeling in residential areas of Jakarta, Indonesia."

Comment 3: The authors to need to revise the Abstract and Introduction for better coherence and clarity; there are too many language errors and disjointed statements.

Thank you. We have done major revisions to the entire language, grammar of the text, and disjointed statements in this Abstract and Introduction to make it as clear, coherent, and understandable as is suggested.

Comment 4: The location coordinates given for Jagakarsa in Lines 265 to 267 need to be corrected since it is an area and not point as the current coordinates suggest.

Thank you. We have revised the writing of the coordinates for the location of the Jagakarsa District. Astronomically, Jagakarsa District is located between longitude 106º,45',0'' East longitude and latitude 6º,15',40.8'' South, according to data from the Jakarta Central Statistics Agency 2019.

Comment 5: The legibility of Fig 1 needs to improve, and the sample locations cannot be observed.

Thank you. We have revised Figure 1 to make it clearer and easy to observe as suggested.

Comment 6: In Lines 90 -91, which ‘dynamics system model’ are the authors referring to? What is the ‘feedback approach’ and how is that linked to the model? That entire paragraph is very disjointed, unclear and needs to be revised for clarity and easy understanding.

Thank you. We have done major revisions to the entire language, grammar of the text, and disjointed statements in this Abstract and section 2.2 to make it as clear, coherent, and easy to understand as suggested.

The System Dynamics concept used in this article is a concept introduced in 1956 by Professor Forrester of the Massachusetts Institute of Technology. This discussion has been pasted in section 2.2. Likewise, what is meant by the 'feedback approach' has been inserted in section 2.2.

As for the explanation in the Abstract, its relation to the system dynamics modeling approach that produces an area's environmental carrying capacity, both in a state of water surplus and water deficit, has been inserted in section 3.4.

Comment 7: Section 2.2 and 2.3 need to be revised totally to appropriately explain the methods employed.

Thank you. We have done major revisions to the entire language, the text's grammar, and disjointed statements in sections 2.2 and 2.3 of this article to make it as clear, coherent, and easy to understand as suggested. To explain the system dynamic approach used for the study area, it has been inserted in section 2.2 of this article.

Comment 8: Authors need to correct errors in the citation of documents, e.g. check Lines 464 – 466.

Thank you. We have corrected and revised the citation of documents for easy understanding as suggested.

Comment 9: From Lines 519-524, Equation 12 is effectively estimation of recharge; so, how can that be increase by another recharge estimate given as Equation 13? Secondly, using recharge alone, as has been under Section 2.4.3 (i.e. Equation 12), to denote available groundwater in the area is erroneous. Authors need to find an appropriate method to estimate the available groundwater for the study.

Thank you. The Thornthwaite-Mather and Folliot model is one of the simplest methods to determine groundwater availability’s initial input variables based on regional water balance. An explanation of the Thornthwaite-Mather and Folliot models’ use has been inserted in section 2.4.3 of this article.

In this study, the initial groundwater availability is influenced by the groundwater recharge variable as a variable that increases groundwater availability and the groundwater quality variable as a variable that decreases groundwater availability. An explanation of this has been inserted in section 3.3 (paragraph 4)

This equation has been widely used by researchers in predicting the amount of groundwater availability. (Dourado-Neto et al., 2010; Gudulas et al., 2013; Mushtaha et al., 2019; Nugroho et al., 2019; Nugroho et a., 2019; Roy & Ophori, 2012).

Comment 10: The entire methodology for the study needs to be explained properly and clearly.

Thank you. We have made major revisions to the entire language, the text's grammar, and disjointed statements in section 2 (Methodology) of this article to make it clearer, coherent, and easy to understand as suggested.

Comment 11: Authors need to clearly explain how they obtained the validation results of population and water demands in Figure 5 and Lines 573-579. What exactly are being validated Fig 5?

Thank you. An explanation of how to obtain the results of the validation of population and water needs in Figure 5 and what to validate is available in section 3.1 (paragraph 2)

Thank you very much for the opportunity to consider our revised manuscript, and we look forward to hearing from you.

Sincerely,

Highlights

Assessment the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia

Erna Savitri*, Djoko M. Hartono, Tri Edhi Budhi Soesilo, Setyo S. Moersidik School of Environmental Sciences, University of Indonesia, Jakarta, Indonesia *Corresponding Author (Email: [email protected])

Abstract

The population problem in Jakarta is one of the inhibiting factors in efforts to improve the quality of the physical environment, thereby causing a social-environmental impact on groundwater imbalance. This research focuses on developing dynamics system modelling using groundwater balance variables. The analytical method carried out on the community water demand subsystem, the land conversion subsystem, and the groundwater availability subsystem. This study aims to assess the sustainability of groundwater balance to simulate groundwater conservation policies in residential areas. This research carried out in the Kemayoran sub-district area with the category of damaged zones and the Jagakarsa sub-district area with the safe zone category. Using secondary data as such demographics, and climatology, to predict subsystem relations from 2020 to 2080. The simulation results showed that before 2069 both regions were surplus water areas with a moderate critical categorize, after 2070 conditions of groundwater availability began to decrease and experienced a water deficit with very severe categories. The results of the study state that to simulate an area's groundwater conservation policy, it is necessary to assess groundwater balance first.

Keywords: groundwater balance; water demand; groundwater availability; system dynamics; groundwater conservation.

Highlights  Groundwater demand and groundwater availability assess groundwater balance.  Dynamic system modeling assesses the carrying capacity of the regional environment  Making infiltration wells can increase groundwater availability.  Reducing water wasteful behavior, making the amount of water needed to decrease.  Carry out groundwater conservation efforts to sustain groundwater balance.

Graphical Abstract Click here to access/download;Graphical Abstract;Graphical abstrac.tiff This article aims to assess the sustainability of groundwater Click here to view linked References balance to simulate groundwater conservation policies in

Assessment the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia

Erna Savitri*, Djoko M. Hartono, Tri Edhi Budhi Soesilo, Setyo S. Moersidik

School of Environmental Sciences, University of Indonesia, Jakarta, Indonesia

*Corresponding Author (Email: [email protected])

Data Availability Statement: Some or all data, models, or codes generated or used

during the study are available from the relevant authors by request. (The data about

modelling results is available on the author and will be provided upon request. Not to be

published).

Assessment the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia

Abstract The population problem in Jakarta is one of the inhibiting factors in efforts to improve the quality of the physical environment, thereby causing a social-environmental impact on groundwater imbalance. This research focuses on developing dynamics system modelling using groundwater balance variables. The analytical method carried out on the community water demand subsystem, the land conversion subsystem, and the groundwater availability subsystem. This study aims to assess the sustainability of groundwater balance to simulate groundwater conservation policies in residential areas. This research carried out in the Kemayoran sub-district area with the category of damaged zones and the Jagakarsa sub-district area with the safe zone category. Using secondary data as such demographics, and climatology, to predict subsystem relations from 2020 to 2080. The simulation results showed that before 2069 both regions were surplus water areas with a moderate critical categorize, after 2070 conditions of groundwater availability began to decrease and experienced a water deficit with very severe categories. The results of the study state that to simulate an area's groundwater conservation policy, it is necessary to assess groundwater balance first.

Author Key Words: groundwater balance; water demand; groundwater availability; system dynamics; groundwater conservation.

1. Introduction

Jakarta, based on data from the Central Statistics Agency (BPS) 2019, with a population growth rate of 1.44% per year it has become the city with the most population density in Indonesia, and this caused by urbanization. The problem of population due to urbanization in Jakarta is one of the inhibiting factors in efforts to improve the quality of the physical environment of settlements, especially on the use of groundwater (Abidin et al., 2011; Kagabu et al., 2012; Kooy et al., 2016; Lubis, 2018; Luo et al., 2019; Onodera et al., 2008). The high use of excessive groundwater has caused concern in some areas due to the possibility of scarcity of groundwater (Chang et al., 2017; Komakech and de

Bont, 2018; Liu et al., 2018; Zhang et al., 2019).

Jakarta's groundwater has become a hope for the people of Jakarta to meet raw water needs. Based on the data of the Jakarta Water Supply System Services in 2017, the Water

Supply Company (PAM) is only able to serve 60% of the total population of Jakarta City, meaning that there are around 40% of the community using groundwater as a source of raw water. River water flowing into Jakarta is also unfit for use because of low-quality problems (Kumar et al., 2017; Luo et al., 2019; Martinus et al., 2018; Paramita and

Ningrum, 2020; Pradafitri et al., 2018). Groundwater recharge that should be source from groundwater catchments originating from southern Jakarta cannot compensate for the very high groundwater absorption rate.

In recent years, many researchers have researched the problem of the sustainability of groundwater balance. Research on groundwater balance in the sub-watersheds of agricultural areas evaluated with an emphasis on groundwater recharge research using water level fluctuations (Prasad and Rao, 2018). Research on groundwater balance by natural replenishment of precipitation, actual evapotranspiration, and surface runoff by using remote sensing approaches and GIS techniques (Wakode et al., 2018). Research to estimate groundwater balance uses a 3D modelling technique approach, in coastal areas with an emphasis on groundwater quality research (Jeihouni et al., 2018). Research on groundwater balance using a system dynamics approach to develop the smart groundwater governance model (Barati et al., 2019).

However, assessment of the sustainability of groundwater balance, especially in residential areas in Jakarta to implement groundwater conservation policies, has not been done much. Therefore, this study proposes the development of a dynamic system model

(Cavana, 2003; Mirchi et al., 2012), to solve environmental problems. The variables used in developing a dynamic system model are variables related to the groundwater balance of an area (Ghasemi et al., 2017; Qiang et al., 2016; Sun and Yang, 2019; Tianhong et al., 2019; Wei et al., 2016). This dynamic system model has several limitations (Ahmadi and Zarghami, 2019; Zomorodian et al., 2018), and many uncertainties due to the dynamic complexity in urban water systems (Garcia et al., 2016; Mashhadi Ali et al.,

2017), and environmental or anthropogenic disturbances (Li et al., 2020; Meng et al.,

2018; Sanchez et al., 2020). However, the results of this modelling show that the intervention plan has a positive effect on the problem of groundwater balance. In this study, an approach with a dynamic system model can be useful as a policy basis for controlling groundwater conservation in residential areas.

2. Methodology

2.1 Study area.

Based on the Jakarta groundwater conservation map, this research conducted in two study areas in Jakarta. Kemayoran sub-district with very poorly groundwater zones and damaged groundwater use zones. Jagakarsa sub-district with excellent groundwater zones and safe groundwater use zones. From the 2019 Jakarta Environmental Status Report

Book, the pollution index in the Kemayoran sub-district is 8.063 with a moderate polluted category, therefore, assumed to be 20% and for Jagakarsa sub-district is 1.783 with a mildly contaminated classification, because of that, estimated to be 10%. Based on data from the Jakarta Meteorology, Climatology, and Geophysics Agency (BMKG), the rate of evaporation is 1,700 mm/year. Kemayoran sub-district based on 2019 data (Fig. 1), has an area of 7.25 km2 with a population of 256,298 people, resulting in a population density of 35,351 people/km2, and a population growth rate of 1.42%. Astronomical it is located between 106º.22'.42"-

106º.58'.18" East Longitude and 5º.19'.12"- 6º.23 '54" South Latitude. This region consists of 8 villages and based on average rainfall data of 2331 mm/year with an average temperature of 28,350C. Kemayoran sub-district has a built-up land area of 650 hectares or 89.66% of the total area and an open-up land area of 75 hectares or 10.34% of the total area (BPS Kemayoran sub-district, 2019).

Jagakarsa sub-district based on 2019 data (Fig. 1), has an area of 25.01 km2 with a population of 401,730 people, resulting in a population density of 16,063 people/km2, and a population growth rate of 3.17%. Astronomically it located between 60.15°.40.8" South

Latitude and 106°.45.0" East Longitude. Jagakarsa sub-district consists of 6 villages and based on average rainfall data of 2463 mm/year with an average temperature of 27,870C.

Jagakarsa sub-district has a built-up land area of 2091 hectares or 83.61% of the total area and an open-up land area of 410 hectares or 16.39% of the total area (BPS, Jagakarsa sub- district, 2019).

Fig. 1. DKI. Jakarta Map shows sampling locations in the study area.

2.2 Analysis of the system dynamics modelling approach for the study area

System dynamics is a method for investigating complex system behaviour over time.

With the feedback approach, the system simulated into a series of interrelated stocks and flows (Balali and Viaggi, 2015; Chen et al., 2017; Ghasemi et al., 2017; Sun and Yang,

2019; Wei et al., 2016; Zomorodian et al., 2018). In this dynamics system model, to obtain groundwater balance, the feedback approach is carried out with the three environmental subsystems. The three subsystems are communities water demand subsystems as a social- environmental model, land conversion subsystems as-built environment models, and groundwater availability subsystems as models of the natural environment. The three subsystems are that will affect the application of groundwater conservation policies in residential areas.

In the system dynamics model, the relationship between variables simulated using the Powersim Constructor Studio 10 software. The variables that influence the model simulation can be poured into Causal Loop Diagrams (Bala et al., 2017; Mirchi et al.,

2012) to see the relationship between variables in the system (Fig. 2). Furthermore, technical analysis carried out by building a Stock Flow Diagram structure (Fig. 3) to be able to do simulations (Bala et al., 2017; Mirchi et al., 2012). Each variable in the dynamics system will to defined in a level equation, rate equation, or constant equation

(Mirchi et al., 2012; Wei et al., 2016). From the Causal Loop and Stock Flow Diagrams, it can see that the three subsystems of groundwater balance influence each other.

Fig. 2. The Third Causal Loop Diagram (CLD) Subsystem

Fig. 3. The Third Stock Flow Diagram (SFD) Subsystem

2.3 Model validation in system dynamics.

The concept of system dynamics models carried out with the feedback approach

(Balali and Viaggi, 2015; Barlas, 1989; Mirchi et al., 2012). Therefore, validation needs doing to be scientifically justified. In this research, the validation carried out is towards structural validation and performance validation. Structural validation emphasizes the belief of examining the logic of thought of the behaviour curve patterns that occur in the model. Behavioural curve growth patterns consist of Reinforcing (Exponential-Growth or Collapse) curve behaviour patterns and Balancing (Decay or Goal-Seeking) behavioural curve patterns (Mirchi et al., 2012). Performance validation is a complementary aspect of the system thinking method.

The purpose of this validation is to obtain confidence in the extent to which the performance of the model is compatible with the real system performance (Ahmadi and

Zarghami, 2019). To find out the validity of the behaviour of the model built, the validity test done by calculating the absolute means error (AME). Absolute Means Error (AME) is a deviation between the average simulation value and the actual value (Barlas, 1989;

Rusiawan et al., 2015). The validation formula used is as follows:

(Si−Ai) AME = x100% (1) Ai

Si Ai Si = ∑ and Ai = ∑ (2) n n

Where: A is the actual value; S is the simulation value; N is the observation time interval.

Valid said if the statistical validity of AME is ≤ 30% (Barlas, 1989; Cavana, 2003;

Rusiawan et al., 2015).

2.4 Descriptive analysis of subsystems.

Groundwater balance is a comparison between the amount of groundwater availability and total water demand (Li et al., 2020). From the prediction results of groundwater balance will get the parameters water balance (NA), water availability index

(IKA), and water use index (IPA). These three parameters used to determine whether water resources in an area are in a surplus or deficit condition. A region said to be a surplus, if the value of NA ≥1, IKA ≥1, and IPA ≤ 25% (Regulation of the Minister of

Environment of the Republic of Indonesia No. 17 of 2009).

2.4.1 Community water demand subsystem as a social-environmental model

This analysis focuses on the water demand of several demand sectors, namely domestic water demand (settlements), non-domestic water demand (public facilities). Total water demand is the amount of water used for various purposes or community activities in the area. In general, the form of the state equation shown below:

Q TWR = Q DWD + Q NWD (3)

Domestic groundwater demand (QDWD) is the amount of shallow groundwater volume needed by the population. QDWD is calculated based on population assumptions (TP) and estimated standard water needs per population (S) according to population groups (150 litters/person/day) and people's behaviour towards groundwater (GW) of 20%. While the demand for non-domestic water (QNWD) is 30% of domestic water demand (Regulation of the Minister of Public Works of the Republic of Indonesia No.18 of 2007).

Q DWD = (TP). (S). (GW) (4)

Q NWD = 30%.Q DWD (5)

Where: Q TWR is total water requirements; Q DWD is domestic water demand; Q NWD is non-domestic water demand; TP is the total population; S is the standard for population water needs; GW is behaviour towards groundwater.

2.4.2 The lands conversion subsystem as a built environment model.

This analysis focuses on the variable of a built-up land area and an open-up land area. A built-up land area is the extent of residential, offices, public services, and social facilities, and an open-up land area is an environmental park area, interactive park, waterfront, green lane road, and burial area. (Regulation of the Minister of Public Works of the

Republic of Indonesia No.18 of 2007).

ALU = ((A Total) (PLU)) + GLU (6)

ALO = A Total - ALU (7)

Where: ALU is the area of a built-up land; ALO is an open-up land area; A Total is the total land area; GLU is the growth of open land rate; PLU is the percentage of existing land use.

2.4.3 The Groundwater availability subsystem as a natural environment models.

The availability of water that calculated is the volume of water from the estimation of rainfall (mm/year) that seeps into shallow groundwater (m3/year) by using the formula

Thornthwaite-Mather (1957) and the Ffolliot method (Dourado-Neto et al., 2010;

Gudulas et al., 2013; Mushtaha et al., 2019; Nugroho et al., 2019; Roy and Ophori, 2012).

Secondary data for groundwater availability, is rainfall data, rainfall volume, evaporation, and topographic data.

T 1,514 i = ( ) (8) 5

α = (6.75 10-7) i3 – (7.71 10-5).i2 – (1.792 10-2) i + 0.4923 (9)

퐿 푁 10.푇 ∝ 퐸푝 = 1.6 ( ) ( ) ( ) (10) 12 30 푖

Based on Regulation of the Minister of Environment of the Republic of Indonesia No. 17 of 2009, the cumulative runoff coefficient (Cro) is calculated by the rational method, and the Cro conversion value for a built-up land area is 0.6 and for an open-up land area is

0.3. Magnitude of cumulative land runoff, using the equation:

Cro = 10. C. I. A (11)

To find out the amount of water that seeps in the soil is determined by calculating groundwater potential using the Ffolliot equation approach:

R = (I - Ep). A. (1 - Cro) (12)

The availability of groundwater could be increase by increasing groundwater recharge.

The groundwater recharge equation (G) is as follows (Regulation of the Minister of

Environment of the Republic of Indonesia No. 17 of 2009):

G = (P - Cro - E) 60% (13)

Where: R is the amount of water that seeps in the soil (m3/year); G is The groundwater recharge (m3); T is the temperature of the air; N is the number of days in a month; L is the actual length of the day; (i) is the accumulation of heat index in a month; Cro is the cumulative runoff coefficient (m3/year); I is rainfall (mm/year); A is the area of land (m2);

10 is a conversion factor from (mm. hectares) to m3; Ep as a potential evapotranspiration

(m/month); P is the volume of rain (m3/year); E is evaporation (m3/year).

3. Results

Based on the evaluation of equations (3), (4), and (5) using the Powersim Constructor

Studio 10 software, getting the results as shown in Figure 4. From the simulation results, it predicted that in 2030, the Kemayoran sub-district obtain a population of 341,037 people with a water demand of 4,866,740 m3, and for the Jagakarsa sub-district, reach a populate of 551,211 people with water demand of 7,846,494 m3. In 2080, an increase in population and water demand, namely for the Kemayoran sub-district by 48.8% and for

Jagakarsa sub-district by 74.7%. Based on the simulation results of structural validation

(Fig. 5) for the two study areas that the events of population increase and water demand follow the theory of the behaviour pattern of Exponential Growth curves (Mirchi et al.,

2012). Based on equations (1) and (2), the results of simulation of performance validation with population growth and water demand, produce AME of 3.5% for the Kemayoran sub-district and AME of 3.88% for Jagakarsa sub-district. The results of validation in both study areas, are said to be valid because the statistical validity of AME is >30%

(Barlas, 1989; Cavana, 2003; Rusiawan et al., 2015).

Fig. 4. Population and water demand prediction.

Fig. 5. Simulation of structure validation of population and water demand.

In the subsystem relationship between population and water demand in this simulation, the scenario carried out is to suppress the pace of infrastructure development.

The purpose of this scenario to reduce the amount of water demand. From the simulation results in 2030, the amount of water demand for the Kemayoran sub-district, it decreased by 4.2%. For the Jagakarsa sub-district, there was a 12.1% reduction. This research also discusses community behaviour towards groundwater influences the decrease in the amount of domestic water demand. From the results of simulations in the two study areas in 2030, reducing the percentage of community behaviour towards groundwater from

20% to 10% resulted in an average reduction in domestic water demand of 33%.

In the land conversion subsystem simulation, the prediction of the area of built-up land is obtained from equation (6), and for an open-up land area obtained from equation

(7). Based on the simulation results in 2030, in the Kemayoran sub-district, the predicted area of a built-up land was reduced by 0.5%, open-up land area increased by 4.6%, and the amount of groundwater availability increased by 3.3%. For Jagakarsa sub-district, the predicted area of built-up land was reduced by 1.6%, open-up land area increased by 13%, and the amount of groundwater availability increased by 8.3%. The results of the structural validation simulation (Fig. 6) in the two study areas, show that the increment in the built-up land area following the theory of the behaviour pattern of the Goal-Seeking curve. While case decrease in an open-up land area, following the concept of the behaviour pattern of the Decay curve (Mirchi et al., 2012).

Fig. 6. Simulation of structure validation against land conversion.

In the simulation of the natural environment model subsystem, the initial prediction of groundwater availability in this study was calculated based on the Thonthwaite-Mather method, with equations (8), (9), and (10). Rational method for calculating Cro with equation (11). The Ffolliot (1980) method for calculating the volume of water seeping to the ground with equations (12) and (13). Based on these equations, the initial groundwater availability prediction in Kemayoran sub-district is 502,952 m3, and in Jagakarsa sub- district is 3,071,959 m3. Based on the simulation of groundwater availability in 2020- 2069, the two study areas concluded to be water surplus areas. For Kemayoran sub- district (Fig. 7), with a moderate critical category (NA value> 1, IKA> 1, IPA 50-100%), while Jagakarsa sub-district (Fig. 8) with a mild critical category (NA value> 1, IKA> 1,

IPA 25-50%).

Fig. 7. Simulation of groundwater balance prediction in the Kemayoran sub-district.

Fig. 8. Simulation of groundwater balance prediction in the Jagakarsa sub-district.

To increase the amount of groundwater availability, one of which is to increase open land, so that groundwater recharge increases. Therefore, the scenario carried out is to suppress the pace of infrastructure development. From the simulation results of groundwater recharge in 2030, in the Kemayoran sub-district, it increased by 4.6%. For

Jagakarsa sub-district, there was an increase of 14%. Another effort to increase the amount of groundwater availability is to reduce the level of groundwater pollution. In this study, groundwater pollution levels are assumed based on groundwater quality in the study area, which is 20% in the Kemayoran sub-district (medium polluted) and 10% in the Jagakarsa sub-district (lightly contaminated). In this study, the scenario carried out by reducing the percentage of groundwater pollution in each study area by 10% and 5%.

From the simulation results in 2030, the availability of groundwater for the Kemayoran sub-district increased by 27%. For Jagakarsa sub-district, an increase of 17.7%.

Based on the 2017 Drinking Water Supply System Service data, PAM Jakarta is only able to serve the Kemayoran sub-district by 60% of the total population and Jagakarsa sub-district by 30% of the total population. Based on this information, there are around

40-70% of the community using groundwater resources as a source of raw water. PAM

Jakarta clean water services are not in line with the 2015 Sustainable Development Goals

(SDG) objectives where must be able to serve 80-100% of the community's clean water needs. Based on the simulation results, PAM Jaya must increase cleaned water production capacity by 2-3% per year, to increase the amount of water supply. This scenario is one of the policies in mobilizing water infrastructure to address additional water demand.

4. Discussions

In this study, for the two study areas, show that domestic water demand has a very dominant influence on total water demand. For this reason, non-domestic water demand variables, no simulation changes are made. Population increase has a positive correlation with the level of domestic water demand (Ashoori et al., 2017; Chen et al., 2020; Okello et al., 2015; Suárez-Varela, 2020; Trasviña-Carrillo et al., 2019; UNESCO, 2015). This increase in population caused by the impact of increasing the pace of infrastructure development, which affects people to migrate to an area. Prediction models in this study can help identify groundwater conservation efforts that will be carrying out. Long-term prediction of water demand is essential for the planning and management of a region's water resources. Therefore, the scenario taken in this study is to suppress the pace of infrastructure development in residential areas.

Based on the 2015 SDGs, community involvement has a decisive role in managing groundwater resources (Jorgensen et al., 2009; Mashhadi Ali et al., 2017; Velis et al.,

2017). Therefore, the scenario that carried out was to reduce the percentage of people's behaviour towards the water to reduce the amount of domestic water demand. In this study, people's behaviour towards groundwater is an excessive public habit of using groundwater for daily life (Koop et al., 2019; Makino et al., 2016).

Rapid population growth as a result of an increase in the pace of infrastructure development, has resulted in a change in land-use and ultimately has an impact on the availability of groundwater in a region (Chemura et al., 2020; Kundu et al., 2017; Mirhosseini et al., 2018; Nugroho et al., 2013; Pulido-Velazquez et al., 2015; Sun et al.,

2016). Therefore in this study, the scenario carried out to maintain open land as water catchment areas is to reduce the pace of infrastructure development in residential areas.

The availability of groundwater in each region is very diverse and different. Various factors that influence groundwater availability are hydrology conditions, soil topography, climatology, geology, and vegetation variations (Condon and Maxwell, 2015; Grinevskii,

2014; Huang et al., 2019; Rukundo and Doğan, 2019; Tukur et al., 2018). One of the variables as an increase in the availability of groundwater is groundwater recharge.

Predictions on groundwater recharge as an increase in groundwater availability generally caused by changes in the pattern of open land areas. Besides, this groundwater recharge also depends on the sustainable management of groundwater resources in a region

(Adhikari et al., 2020; Birhanu et al., 2019; Mohan et al., 2018; Olivares et al., 2019;

Singh et al., 2019). Based on the simulation (Fig. 9), the results show that the groundwater recharge reduced due to a decrease of open-up land area.

Fig. 9. Simulation of groundwater recharge as additional groundwater availability.

One more variable to increase the availability of groundwater is to reduce the level of groundwater quality. If the level of groundwater quality gets higher, the availability of groundwater will decrease (Howard and Gerber, 2018; Kumar et al., 2019; Liyanage and

Yamada, 2017; Patra et al., 2018; Tukur et al., 2018). In this study with reduce the percentage of the level of groundwater quality can increase the availability of groundwater by 17.7-27%.

To analyse groundwater balance, in this study to take advantage the concept of carrying capacity of water resources (Dou et al., 2015; Jia et al., 2018; Meng et al., 2018;

Naimi Ait-Aoudia and Berezowska-Azzag, 2016; Widodo et al., 2015). Based on the simulation (Fig. 10), the results show that in 2020-2069, the two study areas are still in the category of water surplus areas with mild to moderate critical conditions. However, after the 2069 simulation year, the availability of groundwater began to decline, and both study areas categorized as experiencing a water deficit with very critical conditions, and that's when water scarcity occurred.

Fig. 10. Simulation of groundwater imbalance conditions.

In maintain a sustainable groundwater balance, there must be efforts to conserve groundwater from the community and the government (regional or centre). This solution is to be able to create environmental management of groundwater resources, for now, and in the future. Solutions for groundwater conservation effort based on the result findings in this study can be implemented based on sustainable groundwater conservation patterns

(Fig. 11), and implementing a sustainable groundwater conservation program (Fig. 12).

Fig. 11. Sustainable patterns of groundwater conservation.

Fig. 12. Sustainable groundwater conservation program.

5. Conclusion

Land clearing for infrastructure development and uncontrolled settlements indirectly has an impact on the problem of reduced groundwater catchment areas. Such is the case with the Jagakarsa sub-district, where this area is supposed to be the Jakarta water catchment area. The initial conditions of this region are areas with excellent groundwater zones and safe groundwater use zones. However, this region experienced very rapid population growth, which resulted in reduced groundwater catchment areas. Such conditions will produce social-environmental impacts such as groundwater imbalance.

As for the Kemayoran sub-district area, this area densely populated in Central Jakarta.

The Kemayoran sub-district area has not experienced significant changes in terms of population or land use. However, this region is also experiencing problems with groundwater imbalance, because the condition of the area is a very poorly groundwater zone category and a damaged groundwater use zone category. Therefore, with such a situation in the two study areas, it is essential to be of concern to the government (central and regional) in maintaining groundwater balance.

Pressing the pace of development, to conserve groundwater, in this research simulation produced several positive things. The positive results obtained are a decrease in migration resulting in reduced community water demand by 1.7-5%, open land area increased by 1.4-5.4% hence can maintain the catchment area, and groundwater replenishment increased by 1,9-6% causes reduced runoff. But when the pace of development is uncontrollable, the effort to conserve groundwater is with to create a groundwater infiltration media. This groundwater infiltration media can be in the form of yard land covered with grass vegetation or making rainwater catchment wells/rainwater harvesting. This media is useful directly to accommodate and absorb rainwater into the ground. Groundwater conservation by making groundwater infiltration media is one of the programs proposed in this paper.

In this research, the scenario carried out is reducing the percentage of community behaviour towards groundwater, and resulting in a reduction in water demand by 33%.

The other design carried out is to reduce the level of groundwater pollution, and results in an increase in the availability of natural groundwater by 7.8-14.2%. Both scenarios carried out as groundwater conservation efforts. As an implementation of both plans, carried out by providing extension programs to the community regarding savings in groundwater use. This the counselling, provides understanding about the meaning of the environment and the land use that is environmentally friendly, which brings the community can behave positively towards groundwater. Finally, the dynamic system model approach can be applied to assess the balance of groundwater in an area both in Jakarta and other regions throughout Indonesia. This model is useful as a basis for simulating an area's groundwater conservation policy. The availability of groundwater in each region is very diverse and different, hence the use of models can be adapt to the conditions of each area (settlement, industry, or agriculture).

Acknowledgments.

The authors express their sincere thanks to the Jakarta Central Statistics Agency (BPS),

Ministry of Environment of the Republic of Indonesia, and Ministry of Public Works,

Republic of Indonesia, for providing valuable literature for this paper. The authors also show their gratitude to the editors and anonymous reviewers for insightful reviews and useful comments that have led to an extensive Improvement from the initial versions of this paper.

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Fig. 1. DKI. Jakarta Map shows sampling locations in the study area

Fig. 2. The Third Causal Loop Diagram (CLD) Subsystem

community + behavior

+ hotel needs R +

numbers + of hotel hotel water the water demand standard for polution + hotel water the standard + + needs percentage for population + of migration water needs + out migration Water demand out + domestic water demand + + + community + + + needs + + + + the behavior + IPA water IKA environmental birth R the total toward balance carrying capacity + B death of the region population groundwater + + Non domenstic - + + + water demand + percentage + percentage the standard for + of birth + of death + migration non domestic water + percentage population in needs reduced increased density of migration B groundwater R in the area of avalilability of availability availability of + developed groundwater groundwater + + land - + rasio of built evaporation land R rate area + + + + + land + + the pace of conversion evaporation + infrastructure development - + + rainfall groundwater B volume - rasio of open recharge + + land the area of open rainfall + land + + + Runoff Fig. 3. The Third Stock Flow Diagram (SFD) Subsystem.

hotel PAM water availability Community water demand hotel rate Persen Losses subsystem as a social- community behavior served percentage ecological model. percentage of growth PAM water production hotel lack of clean water the standar for hotel hotel water demand water needs the standard for IPA percentage migration population water incerased PAM out behavior toward needs water rate groundwater PAM existing water balance percentage of PAM water water demand migration out rate domestic water water supply demand IKA the standar for non population domestik water need

decreased increased groundwater groundwater birth rate death rate availability availabilty

migration in rate non domestik water demand percentage of birth percentage of death groundwater availability

percentage migration water pollution in

built land built land existing coefiisien

built land rate built land built land Cro

cumulative Cro open land coefisien

area runoff rainfall groundwater open land Cro rainfall volume recharged

evaporation rate

open land The land conversion the pace of open land rate The groundwater availability subsystem as a built infrastucture subsystem as a natural environment model. development evaporation environment model

Fig. 4. Population and water demand prediction.

Fig. 5. Simulation of structure validation of population and water demand.

Fig. 6. Simulation of structure validation against land conversion.

Fig. 7. Simulation of groundwater balance prediction in the Kemayoran sub-district.

Fig. 8. Simulation of groundwater balance prediction in the Jagakarsa sub-district.

Fig. 9. Simulation of groundwater recharge as additional groundwater availability.

Fig. 10. Simulation of groundwater imbalance conditions.

Fig. 11. Sustainable patterns of groundwater conservation.

Fig. 12. Sustainable groundwater conservation program.

Manuscript File Click here to view linked References

Assessing the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia

Erna Savitri*, Djoko M. Hartono, Tri Edhi Budhi Soesilo, Setyo S. Moersidik

School of Environmental Sciences, University of Indonesia, Jakarta, Indonesia

*Corresponding Author (Email: [email protected])

Assessing the sustainability of groundwater balance using dynamics system modelling in the residential area Jakarta, Indonesia

Abstract The purpose of this groundwater balance study is to see whether the status of the carrying capacity of the study area is a water surplus area or a water deficit area. The study area in this research is residential in (1) Kemayoran District, Central Jakarta with a damaged zone category, (2) Jagakarsa District, South Jakarta with a safe zone category. Therefore, this groundwater balance research focuses on developing dynamic system modeling as a feedback approach. In this research, the feedback approach is carried out based on the community water needs subsystem, land conversion subsystem, and groundwater availability subsystem. The model simulation is carrying out to predict the 2020-2080 subsystem relationship. Based on the results of the analysis, it shows that before 2069 the two areas a water surplus areas with the medium critical category. However, in 2070 onwards, groundwater availability in the region begins to decline and experiences a water deficit in a very severe level. As a prevention of groundwater imbalance in residential areas, the research results obtained several strategies for implementing groundwater conservation policies, namely (1) reducing the level of community dependence on groundwater, (2) increasing water conservation areas, (3) reducing the level of groundwater pollution, (4) decrease activities that have an impact on land-use change.

Author Key Words: groundwater balance; water demand; groundwater availability; system dynamics; groundwater conservation.

1. Introduction

The City of Jakarta is the most populous in Indonesia based on population growth rate data of 1.44% per year that is generally caused by urbanization (BPS.DKI.Jakarta,

2019). Population problems due to urbanization in Jakarta are one of the inhibiting factors in efforts to improve the physical quality of the residential environment, especially in the use of groundwater (Abidin et al., 2011; Kagabu et al., 2012; Kooy et al., 2016; Lubis, 2018; Luo et al., 2019; Onodera et al., 2008). The high use of groundwater that is excessive has resulted in an imbalance of groundwater in several areas (Chang et al.,

2017; Komakech & de Bont, 2018; Liu et al., 2018; Zhang et al., 2019).

The high use of groundwater in Jakarta, based on data obtained from the 2019 Jakarta

Industry and Energy Office that the amount of groundwater use in Jakarta has increased by 27.6%. Based on the city/regency area, South Jakarta is the area that uses the highest groundwater in Jakarta, namely 3,768,226 m3 (2018) and 4,384,123 m3 (2019). This problem is because South Jakarta has many office and residential buildings. North Jakarta and the Thousand Islands area used the lowest groundwater because groundwater in this area has been intruded by seawater.

There are several reasons why the people of Jakarta use groundwater to meet their raw water needs. Based on the Jakarta Drinking Water Company is only able to serve

59.45% of Jakarta’s total population, around 40.55% of the community uses groundwater as a water source for their daily lives. Besides, based on river water flowing to Jakarta, it is also not feasible for use due to low-quality problems, which means that people cannot use river water as a source of water (Kumar et al., 2017; Luo et al., 2019; Martinus et al.,

2018; Paramita & Ningrum, 2020; Pradafitri et al., 2018).

Based on the background mentioned above, then most people use groundwater excessively. Groundwater withdrawal is high enough to cause impacts on the groundwater environment, including lowering the groundwater table and reducing the potential for groundwater in aquifers. Besides, based on the groundwater infiltration area, which should be a source of groundwater infiltration from South Jakarta, it cannot compensate for the very high-level of groundwater extraction (Samsuhadi, 2009). This condition will lead to an imbalance in groundwater and can threaten the sustainability of the city. It also happened in the Kemayoran and Jagakarsa Districts, as the study areas in this study. In Jagakarsa District, this area is supposed to be Jakarta's water catchment area.

This area's initial state is an excellent groundwater zone and a safe groundwater use zone.

However, the region is experiencing rapid population growth, resulting in reduced groundwater catchment areas. Such conditions will result in socio-environmental impacts such as groundwater imbalance. As for the Kemayoran sub-district, this area is the densely population in Central Jakarta. The region of the Kemayoran district has not experienced significant changes in terms of people or land use. However, this area also experiences groundwater imbalance problems because the area's condition is a badly groundwater zone category and a damaged groundwater utilization zone category, which originated from the excessive use of groundwater from the local community.

Numerous indicators and assessment tools have been developing by many researchers for assessing the sustainability of groundwater balance. Research on groundwater balance in agricultural sub-watersheds is evaluated with an emphasis on groundwater infiltration using water level fluctuations (Prasad & Rao, 2018). Research on groundwater balance with natural filling of precipitation, actual evapotranspiration, and surface runoff using remote sensing approaches and GIS techniques (Wakode et al.,

2018). Research groundwater balance in coastal areas is evaluating with an emphasis on groundwater quality using the 3D modeling technique approach (Jeihouni et al., 2018).

Research on groundwater balance uses a system dynamics model approach to develop a smart groundwater governance model (Barati et al., 2019).

However, there has not been much to assess groundwater balance sustainability in implementing groundwater conservation policies, especially in residential areas in

Jakarta. Therefore, this research focuses on developing dynamic systems modeling as a feedback approach (Ghasemi et al., 2017; Qiang et al., 2016; B. Sun & Yang, 2019; Tianhong et al., 2019; Wei et al., 2016) to the sustainability of groundwater balance in residential areas of Jakarta. The feedback approach in this study of carrying out with the three environmental subsystems, namely the community water needs subsystem, land conversion subsystem, and groundwater availability subsystem, as variables in developing in dynamic modeling systems. The three subsystems are variables that will be simulated and will influence the implementation of groundwater conservation policies in residential areas. In the system dynamics model, these variables from the three subsystems are put into a Causal Loop Diagram (CLD) to see the relationship between variables in the system. Then quantified and simulated using Stock and Flow Diagrams

(SFD). Through CLD and SFD, all scenarios carried out to assess groundwater balance in residential areas can have the ability to influence future action. This dynamic system model has several limitations (Ahmadi & Zarghami, 2019; Zomorodian et al., 2018) and many uncertainties due to the complexity of dynamics in urban water systems (Garcia et al., 2016; Mashhadi Ali et al., 2017), and environmental or anthropogenic disturbances (Li et al., 2020; Meng et al., 2018; Sanchez et al., 2020). However, this modeling result indicates a positive effect on the groundwater balance problem. In this dynamic systems model approach, several strategies are obtaining that can be used as a base for simulating groundwater conservation policies.

2. Methodology

2.1 Study area.

Based on the Jakarta groundwater conservation map, this research is carrying out in two study areas in Jakarta. Kemayoran District with very poorly groundwater zones and damaged groundwater use zones. Jagakarsa District with excellent groundwater zones and safe groundwater use zones. From the 2019 Jakarta Environmental Status Report Book, the pollution index in the Kemayoran District is 8.063 with a moderate polluted category, therefore, assumed to be 20% and for Jagakarsa District is 1.783 with a mildly contaminated classification, because of that, estimated to be 10%. Based on data from the

Jakarta Meteorology, Climatology, and Geophysics Agency, the rate of evaporation is

1,700 mm/year.

Kemayoran District, based on 2019 data (Fig.1), has an area of 7.25 km2 with a population of 256,298 people, resulting in a population density of 35,351 people/km2 and a population growth rate of 1.42%. Astronomically is location between the longitude lies on 106º,22',42'' East - 106º,58',18'' East and latitude 5º,19',12'' S - 6º,23',54''

South. Kemayoran District consists of eight villages, based on average rainfall data of

2,331 mm/year with an average temperature of 28.350C. Kemayoran District has a built- up land area of 650 hectares or 89.66% of the total area, and an open-up land area of 75 hectares or 10.34% of the total area (BPS.Kemayoran District, 2019).

Jagakarsa District, based on 2019 data (Fig.1), has an area of 25.01 km2 with a population of 401,730 people, resulting in a population density of 16,063 people/km2 and a population growth rate of 3.17%. Astronomically is location between the longitude lies on 106º,45’,0'' East and latitude 6º,15',40.8'' South. Jagakarsa District consists of six villages and based on average rainfall data of 2,463 mm/year with an average temperature of 27.870C. Jagakarsa District has a built-up land area of 2,091 hectares or 83.61% of the total area, an open-up land area of 410 hectares or 16.39% of the total area (BPS.Jagakarsa

District, 2019)

Fig. 1. Jakarta Province Map shows sampling locations in the study area

2.2 Analysis of the system dynamics modelling approach for the study area.

The concept of system dynamics was first introduced in 1956 by Forrester (Forrester,

1961). System dynamics is a method for investigating complex system behavior over time. There are three main elements in System Dynamics, namely feedback loops, variables, and equations. Conceptually, the feedback concept is at the core of the System

Dynamics approach, which is defining as a closed chain of cause and effect. The feedback diagram in the conceptual model is known as the Causal Loop Diagram (CLD), which is then quantified and simulated using Stock and Flow Diagrams (SFD) (Sterman, 2000).

These diagrams are tools for conceptualizing the structure of a complex system and for communicating model-based insights. Intuitively, feedback occurs when information resulting from multiple actions travels through the system and ultimately returns in some form to its point of origin, and potentially influencing future actions. If the tendency in a loop is to reinforce the initial process, the feedback diagram is called a positive or reinforcing feedback loop. If the trend is to oppose the initial action, the feedback diagram is called a negative feedback loop or balancing. Combining from the process of reinforcing and balancing circular causal feedback can produce dynamic patterns. With this feedback approach, the system simulated into a series of interrelated stocks and flows

(Balali & Viaggi, 2015; C. Chen et al., 2017; Ghasemi et al., 2017; B. Sun & Yang, 2019;

Wei et al., 2016; Zomorodian et al., 2018). Each variable in system dynamics will be defining in level equations, rate equations, or constant equations (Mirchi et al., 2012; Wei et al., 2016).

In this study, to simulating the sustainability of groundwater balance in residential areas in Jakarta is carried out with the system dynamics method. The groundwater balance is the relationship between groundwater availability and the total water demand as information on the state of water in an area under water surplus or deficit (Li et al., 2020).

To obtain groundwater balance, the feedback approach of carrying out with the three environmental subsystems. The three subsystems are communities water demand subsystems as a social-environmental model, land conversion subsystems as-built environment models, and groundwater availability subsystems as models of the natural environment. The three subsystems are variables that will be simulated and will influence the implementation of groundwater conservation policies in residential areas. In the

System Dynamics model, analysis of the three subsystems is carrying out using the

Powersim Constructor Studio 10 software. The variables from the three subsystems that affect the model simulation can be poured into the Causal Loop Diagram (Fig.2) to see the relationship between variables in the system (Bala et al., 2017; Mirchi et al., 2012).

To carrying out the simulation, technical analysis is carrying out with the Stock and Flow

Diagram structure shown in Figure 3 (Bala et al., 2017; Mirchi et al., 2012). From the

Causal Loop and Stock and Flow Diagram, able will be seen that the three subsystems of groundwater balance influence each other.

Fig. 2. The Third Causal Loop Diagram (CLD) Subsystem

Fig. 3. The Third Stock Flow Diagram (SFD) Subsystem

2.3 Model validation in system dynamics.

Because the system dynamics models are carrying out with a feedback approach

(Balali & Viaggi, 2015; Barlas, 1989; Mirchi et al., 2012), that verification needs to be over to that could be scientifically justified. In this study, the validation that is carrying out was structural validation and performance validation. The structural verifying is carrying out to examine the growth pattern of the behaviour curve that occurs in the model. The growth pattern of the behaviour curve consists of the Reinforcing

(Exponential-Growth or Collapse) behaviour pattern and the Balancing (Decay or Goal-

Seeking) behaviour pattern (Mirchi et al., 2012). Meanwhile, performance validation is carrying out to check the validity results between the simulation value and the actual value that occurs in the model (Ahmadi & Zarghami, 2019). Performance validity test, performed by calculating absolute means error. Absolute Means Error (AME) is the deviation between the average simulation value and the actual (Barlas, 1989; Rusiawan et al., 2015). The validation formula used is as follows:

(Si−Ai) AME = x100% (1) Ai

Si Ai Si = ∑ and Ai = ∑ (2) n n

Where: A is the actual value; S is the simulation value; N is the observation time interval.

Valid said if the statistical validity of AME is ≤ 30% (Barlas, 1989; Cavana, 2003;

Rusiawan et al., 2015).

2.4 Descriptive analysis of subsystems.

2.4.1 Community water demand subsystem as a social-environmental model

This analysis discusses the water demand of several demand sectors, namely domestic water demand (settlements), non-domestic water demand (public facilities). Total water demand is the amount of water used for various purposes or community activities in the area. In general, the form of the state equation shown below:

Q TWR = Q DWD + Q NWD (3)

Domestic water demand (QDWD) is the total volume of water required by the population.

QDWD is calculated based on population assumptions (TP) and estimated water needs per population (S) according to population groups (150 litters/person/day) and community behaviour towards groundwater (GW) 20%. Meanwhile, non-domestic water needs

(QNWD) are 30% of domestic water needs (Minister of Public Works of the Republic of

Indonesia, Regulation No.18, 2007). Q DWD = (TP). (S). (GW) (4)

Q NWD = 30% (Q DWD) (5)

2.4.2 The lands conversion subsystem as a built environment model.

This analysis discusses the variable area of constructed land and open land area. The size of built land is the area of settlements, offices, public services, and social facilities, while the open-land site is an environmental park, interactive park, waterfront, green lane, and burial area (Minister of Public Works of the Republic of Indonesia, Regulation No.18,

2007)

ALU = ((A Total) (PLU)) + GLU (6)

ALO = A Total - ALU (7)

Where: ALU is the area of a built-up land; ALO is an open-up land area; A Total is the total land area; GLU is the growth of open land rate; PLU is the percentage of existing land use.

2.4.3 The Groundwater availability subsystem as a natural environment models.

In this study, the amount of water is seeping into the ground is assumed to be the initial amount of groundwater availability. The amount of water seeping into the soil was estimated using the Thornthwaite-Mather formula (1957) and the Ffolliot method

(Dourado-Neto et al., 2010; Gudulas et al., 2013; Mushtaha et al., 2019; A. R. Nugroho et al., 2019; Roy & Ophori, 2012). The Thornthwaite-Mather equation (1957), used to obtain the value of Ep (potential evapotranspiration) by using the influence of the climate element mean temperature. T 1,514 i = ( ) (8) 5

α = (6.75 10-7) i3 – (7.71 10-5) i2 – (1.792 10-2) i + 0.4923 (9)

퐿 푁 10.푇 ∝ 퐸푝 = 1.6 ( ) ( ) ( ) (10) 12 30 푖

Where: Ep as a potential evapotranspiration (m/month); T is the temperature of the air; N is the number of days in a month; L is the actual length of the day; (i) is the accumulation of heat index in a month.

Meanwhile, the Folliot equation is using to estimate the amount of water that seeps into the ground. This mathematical approach from Ffolliott (1980) is influenced by the amount of rainfall, evaporation (evapotranspiration), and the area of land use, as groundwater potential. Therefore, based on the resulting this Folliot equation, it is used as the initial input variable for groundwater availability in the Equation Level on Stock and Flow

Diagrams for system dynamics models. The Folliot equation approach is

R = (I - Ep). A. (1 - Cro) (11)

For the value of the cumulative runoff coefficient (Cro), based on the Regulation of the

Minister of Environment of the Republic of Indonesia No. 17 of 2009, calculated using the rational method, and the conversion value of Cro for the built-up land area is 0.6 and for an open-up land area is 0.3. The amount of cumulative runoff, using the equation:

Cro = 10. C. I. A (12)

Where: R is the amount of water that seeps into the soil (m3/year); Cro is the cumulative runoff coefficient (m3/year); Rf is rainfall (mm/year); A is the area of land (m2); 10 is a conversion factor from mm. hectares to m3; Ep as a potential evapotranspiration

(m/month).

Increasing the availability of groundwater can be done by increasing groundwater recharge. Based on the Regulation of the Minister of Environment of the Republic of

Indonesia Number 17 of 2009, groundwater recharge is strongly influencing by the area of open land, the volume of rainfall, and the rate of evaporation. This groundwater recharge variable is an inflow variable for the addition of groundwater availability in the

Rate equation in the Stock and Flow Diagram for system dynamics models. The equation for calculating groundwater recharge (G) is as follows (Minister of Environment of the

Republic of Indonesia, Regulation Number 17, 2009):

G = (P - Cro - E) 60% (13)

Where: G is The groundwater recharge (m3); P is the volume of rain (m3/year); E is evaporation (m3/year); Pi is Percentage of groundwater recharge (60%).

3. Results

3.1 Simulation of community water demand subsystem as a social-environmental

model

In this study, the community water demand subsystem as a social-environmental model is analysed based on population size changes on community water demand changes. Based on the evaluation of equations (3), (4), and (5) using the Powersim

Constructor Studio 10 software, the prediction results are obtaining from the population and community water demand. The results are showing in Figure 4. With the increase in population every year, in 2080, it is estimated that there will be an increase in community water demand, namely for the Kemayoran District 52.82% and the Jagakarsa District of

89.70%. Based on the simulation results, population increase is positively correlating with the population's need for water (Ashoori et al., 2017; X. Chen et al., 2020; Okello et al., 2015; Suárez-Varela, 2020; Trasviña-Carrillo et al., 2019; UNESCO, 2015). This water demand prediction is needed for planning and managing water resources in an area.

As an effort to conserve groundwater, in this simulation, the scenario is to reduce the rate of infrastructure development in residential areas by 0.5% from 1% in Kemayoran

District and 1.5% from 3% for Jagakarsa District. Based on the simulation results in 2080, there is a reduction in water demand of the population in Kemayoran District by 13% and

Jagakarsa District by 36.8%.

In this simulation, the community water needs subsystem as a social-environment is validated against the population and water needs. Structural validation is carried out based on simulations with a dynamic system model. The validation results (Fig. 5) for the two study areas show that the increase in population and water demand increase follow the

Reinforcing Exponential Growth curve theory (Mirchi et al., 2012). For performance validation, it is based on equations (1) and (2). Validation of population and water demand is carried out using time series data 2013-2019. The validation value is that actual data is compared with the simulation data resulting from the dynamic system model. Based on the validation results (Fig. 6), for Kemayoran District, it produces AME 3.5%, and for

Jagakarsa District, it produces AME 3.88%. The validation results in both study areas are valid because the statistical validity of AME is <30% (Barlas, 1989; Cavana, 2003;

Rusiawan et al., 2015).

In the community water demand subsystem as a socio-environmental model, an analysis also carries out community behaviour’s influence on community water demand changes. In this study, the scenario applied reduces community behaviour towards groundwater in residential areas in both study areas by 10% from the previous 20%.

Based on the simulation results in 2080, there will be a decrease in population water needs by 33%. This scenario is one of the strategies for implementing groundwater conservation policies.

Fig. 4. Population and water demand prediction.

Fig. 5. Simulation of structure validation of population and water demand.

Fig. 6. Simulation of performance validation of population and water demand.

3.2 Land conversion subsystem simulation as a built environment model.

In this study, the land conversion subsystem as a model for the built environment is analyzed based on the influence of built land and open land on groundwater availability changes. In the prediction simulation, the built-up land area is obtaining from equation

(6) and an open-up land area from equation (7). As an effort to conserve groundwater, in this simulation, the scenario is to reduce the rate of infrastructure development in residential areas, namely 0.5% from 1% in Kemayoran District and 1.5% from 3% for

Jagakarsa District. Based on predictions 2080, in the Kemayoran District, the predicted area of built-up land will decrease by 1.18% (from 687 ha to 671 ha), open-up land area will increase 17.39% (from 38 ha to 54 ha). The amount of groundwater availability increased by 16.31% (from 9,674,102 m3 to 13,443,434 m3). Jagakarsa District, the predicted area of built-up land, will decreased by 2% (from 2,448 ha to 2,352 ha), open- up land will increased by 47.5% (from 53 ha to 149 ha). The amount of groundwater availability increased by 40.96% (from 38,138,121 m3 to 91,047,981 m3).

In the simulation of the land conversion subsystem as a model for the built environment, validation is carrying out to show the behavior pattern of the built-up land area and the open-up land area. Based on the analysis of simulating the structure validation simulation (Fig. 7) in the two study areas, the increase in the built-up land area follows the Balancing Goal-Seeking Curve behavior pattern theory. Meanwhile, the case of decreasing open-up land area follows the concept of the Balancing Decay Curve behavior pattern (Mirchi et al., 2012).

Fig. 7. Simulation of structure validation against land conversion.

3.3 Simulation of groundwater availability subsystem as a natural environment model

In this study, the groundwater availability subsystem as a natural environmental model is analysed based on the influence of groundwater recharge as a variable that increases groundwater availability and groundwater quality as variables that reduce groundwater availability. As an initial prediction of groundwater availability simulation in this study, calculated based on the Thonthwaite-Mather Method, to obtain the parameters of the heat index and potential evapotranspiration with equations (8), (9) and

(10). Rational method for calculating Cro with equation (12). The Ffolliot (1980) method for estimating water volume seep into the ground with equations (11). As for the results of these calculations, the prediction of the initial groundwater availability in Kemayoran

District is 502,952 m3, and in Jagakarsa, it is 3,071,959 m3.

In the analysis of groundwater recharge in this study, the objective is to determine how much influence it has on groundwater availability. In this study, the prediction of groundwater recharge is obtaining from equation (13). The groundwater recharge variable in the simulation is a variable that acts as an additional variable of the groundwater availability variable. Changes in the pattern of open areas significantly affect the groundwater recharge variable. The simulation results are presenting in Figure 8. The picture explains that based on data on open-up land area, which has decreased every year due to an increase in the development rate, a groundwater recharge graph, also falls. With reduced groundwater recharge, the potential for groundwater availability will also decrease. As an effort to conserve groundwater, in this simulation, the scenario is to reduce the rate of infrastructure development in residential areas by 0.5% from 1% in

Kemayoran District and 1.5% from 3% for Jagakarsa District. Based on predictions in

2080 in the Kemayoran District, groundwater recharge is predicting to increase by 17.6%

(from 1,833,431 m3 to 2,617,121 m3). Jagakarsa District, in 2080, predicted groundwater recharge to increase by 48.6% (from 2,655,322 m3 to 7,676,487 m3).

Figure 8. Simulation of groundwater recharge as additional groundwater availability

In research, the groundwater availability subsystem also analyses groundwater pollution as a variable that reduces groundwater availability. The analysis of groundwater pollution levels in this study area aims to determine how much influence it has on groundwater availability. Groundwater pollution level variables in the simulations carried out are variables that act as outflow variables of the groundwater availability variable. In this study, groundwater pollution is based on groundwater quality in the study area, namely 20% in Kemayoran District (moderately polluted) and 10% in Jagakarsa District

(lightly contaminated). In this study, one of the efforts to implement groundwater conservation is to reduce groundwater pollution by 18% from 20% in Kemayoran District and 8% from 10% for Jagakarsa District. Based on predictions in 2080, there will be an increase in groundwater availability for Kemayoran District by 5.6% and Jagakarsa

District by 15.6%.

3.4 The Groundwater Balance Simulation

In this study, to simulating the sustainability of groundwater balance in residential areas in Jakarta is carried out with the system dynamics method. From the prediction of groundwater balance, it is obtaining water balance parameters (NA), water availability index (IKA), and water use index (IPA). The three groundwater balance parameters determine the groundwater carrying capacity (Minister of Environment of the Republic of Indonesia, Regulation Number 17, 2009). This study's system dynamics modelling approach results in an area's environmental carrying capacity, both in a state of water surplus and water deficit. Based on the projected groundwater availability in Kemayoran district in 2020-2069 (Fig.9), the value of NA >1, IKA >1, IPA of 50% - 100%, this region is classifying as a surplus area with moderate critical condition. But in 2070 onwards, groundwater availability began to decrease, where the value of NA <1, IKA <1,

IPA >100%, this condition is categorized as having a severe critical water deficit. For

Jagakarsa district, the projected groundwater availability in 2020-2065 (Fig.10), the value of NA >1, IKA >1, IPA of 25% - 50%, this region is classifying as a surplus area with mild critical conditions. But in 2065 onwards, groundwater availability began to decrease, where the value of NA <1, IKA <1, IPA> 100%, this condition is categorized as a water deficit area with a critically heavy category.

Based on the simulation results of the prediction of groundwater balance using the system dynamics model approach (Fig.11), it predicts that groundwater availability has begun to decline, and the two study areas are classifying as experiencing a water deficit in a very critical condition. For this reason, it is necessary to be aware of when this groundwater imbalance conditions. Therefore, with such situations in the two study areas, it is essential to pay attention to the central/regional governments/other organizations in maintaining groundwater balance by implementing groundwater conservation programs.

Figure 9. Simulation of groundwater balance prediction in Kemayoran District.

Figure 10. Simulation of groundwater balance prediction in Jagakarsa District.

Figure 11. Simulation of groundwater imbalance conditions.

3.5 Contribution efforts from the Jakarta Drinking Water Company Based on data from the 2017 Drinking Water Supply System Service, PAM Jakarta can only serve 59.45% of Jakarta's total population. This Jakarta PAM service is not in line with the 2015 SDG goals, where piped clean water services must operate 80% or even 100% of the community's clean water needs. Therefore, it is necessary to analyse the performance of PAM Jakarta. The analysis was carried out based on secondary data, namely the service level of 60%, the leakage rate at the distribution of 50%, the number of house connections 80 litters/person/day, and the installed pipe flow capacity of 200 litters/second. The simulation results show that PAM Jakarta's ability can meet the total household water consumption until 2064. Therefore, in this simulation, a scenario is carried out by reducing the distribution leakage rate from 50% to 30%. The scenario results show increasing PAM Jakarta water availability by 22% -25% (2080), and the balance of PAM Jakarta water becomes stable until 2090. In this simulation, the next scenario is carrying out by increasing the service level from 60% to 80% to meet the

SDGs goals. This simulation shows that the number of water users of Jakarta PAM increase by 14%. That matter has resulted in the availability of PAM Jakarta water becoming a water deficit in 2052. Therefore, a follow-up scenario is carrying out by increasing the pipeline installation capacity from 200 litters/second to 400 litters/second.

The simulation results show an increase in Jakarta's water supply by 33%.

4. Discussions

In this study, the community water demand subsystem as a social and environmental model discusses the relationship between population changes and changes in domestic water demand. In this research for the two study areas, domestic water demand has a very dominant influence on total water demand. Therefore, for the variable non-domestic water demand, no simulation is done. In this study, the population was influence by four variables, namely the birth rate, mortality rate, in-migration rate, and out-migration rate.

This the number of population variable is an inflow variable in the Equation Level on the

Stock and Flow Diagram for a system dynamics model. The increase in population caused by the impact of the increased rate of infrastructure development, which causes people to migrate to an area. Therefore, the scenario is carrying out in this study is to reduce the rate of infrastructure development in residential areas.

In the study of the subsystem of community water needs as a social and environmental model, another analysis conducted was to discuss the relationship between changes in community behaviour towards groundwater and domestic water needs. Community behaviour towards water in this study is a habit of the community that is excessive in utilizing groundwater for daily life (Koop et al., 2019; Makino et al., 2016).

Therefore, in this study, the scenario as groundwater conservation efforts is carried out by involving the community to reduce community behaviour towards groundwater in residential areas. Because based on the 2015 SDGs, community involvement is crucial in managing groundwater resources (Jorgensen et al., 2009; Mashhadi Ali et al., 2017; Velis et al., 2017).

In the land conversion subsystem as a model for the built environment, the study discusses the relationship between built land and open land on groundwater availability changes in the study area. Rapid population growth as a result of the increasing rate of infrastructure development has resulted in changes in land use and ultimately has an impact on the availability of groundwater in a region (Chemura et al., 2020; Kundu et al.,

2017; Mirhosseini et al., 2018; P. Nugroho et al., 2013; Pulido-Velazquez et al., 2015; Z.

Sun et al., 2016). Therefore, the analysis carried out in this study aims to maintain open land as a water catchment area. The change in land use in a residential area is based on the area’s rate of infrastructure development activities. Therefore, in this study, the scenario that is carrying out reduces infrastructure development in residential areas. This scenario is one of the strategies for implementing groundwater conservation policies in residential areas, namely to minimize activities that result in changes in land-use.

In the subsystem of groundwater availability as a natural environment model, this study discusses groundwater recharge’s relationship as a variable that increases groundwater availability and groundwater quality as a variable that reduces groundwater availability in the study area. Groundwater availability in each region is very diverse and different. Various factors that affect groundwater availability are hydrological, soil topographical, climatological, and geology conditions (Condon & Maxwell, 2015;

Grinevskii, 2014; Huang et al., 2019; Rukundo & Doğan, 2019; Tukur et al., 2018).

Therefore, this groundwater availability study was based on average temperature, rainfall, cumulative runoff coefficient, evapotranspiration rate, and land area of each study area.

In this analysis, the sustainability of groundwater availability in the study area is strongly influencing by two variables, namely the groundwater recharge variable as the inflow variable of groundwater availability and the groundwater quality variable as the outflow variable of groundwater availability.

One of the variables as an increase in the availability of groundwater is groundwater recharge. Predictions on groundwater recharge as an increase in groundwater availability generally caused by changes in the pattern of open land areas. Besides, groundwater recharge also depends on groundwater resources’ sustainable management in a region

(Adhikari et al., 2020; Birhanu et al., 2019; Mohan et al., 2018; Olivares et al., 2019;

Singh et al., 2019). Based on the simulation results show that the groundwater recharge variable is strongly influenced by the variable rate of infrastructure development, which results in changes in the area of open land, and in the end, impacts the potential availability of groundwater. Therefore, in this study, the scenario that is carrying out reduces infrastructure development in residential areas. This scenario is one of the strategies for implementing groundwater conservation policies in residential areas, namely to increase groundwater conservation areas.

Another variable that can influence groundwater availability is the level of groundwater pollution. The higher the level of groundwater pollution, the less groundwater availability can be utilized by the community (Howard & Gerber, 2018;

Kumar et al., 2019; Liyanage & Yamada, 2017; Patra et al., 2018; Tukur et al., 2018).

Therefore, in this simulation, to conserve groundwater to increase groundwater availability, the scenario is to reduce groundwater pollution through outreach to the community. Socialization to residents aims to understand environmentally friendly land use to have a positive attitude towards groundwater. Through outreach to the community, it is hoping that groundwater pollution can be reducing. This scenario is one of the strategies for implementing groundwater conservation policies in residential areas, namely increasing community empowerment activities to play a role in maintaining and reducing levels of groundwater pollution.

To analyse the groundwater balance in this study utilizes the concept of carrying capacity of water resources (Dou et al., 2015; Jia et al., 2018; Meng et al., 2018; Naimi

Ait-Aoudia & Berezowska-Azzag, 2016; Widodo et al., 2015). The concept of carrying capacity of water resources, namely the ratio between groundwater availability and water needs. This concept aims to determine the status of the environment’s carrying capacity

(Minister of Environment of the Republic of Indonesia, Regulation Number 17, 2009).

Based on that the water resources carrying capacity concepts, it can know in general whether groundwater resources in an area are in a state of surplus or deficit. Based on the simulation results in this study, it is estimating that groundwater availability will begin to decline. Both study areas experience a water deficit in a very critical condition. Therefore, given the two study areas” situation, it is essential to pay attention to the central/regional governments/other organizations to implement groundwater conservation programs immediately

This research also discusses the contribution efforts of PAM Jakarta. Based on the simulation results, to increase clean water availability, the Jakarta PAM must reduce the distribution leakage rate from 50% to 30%. Meanwhile, to meet the SDGs goal of 80% service level, PAM Jakarta must increase the installed pipe flow capacity from 200 litters second to 400 litters/second. The simulation results show that PAM Jakarta can increase water supply by 33%. This scenario is one way to implement groundwater conservation in residential areas, namely reducing community dependence on groundwater.

5. Conclusion

Pressing the rate of development, as an effort to conserve groundwater, in this research simulation produces several positive things. The positive results obtained were a decrease in the population, which resulted in a reduction in the water needs of the people by 13% -36.8%, the open land area increased by 17.39% -47.5% so that it could maintain the water catchment area, and groundwater recharge increased by 17, 6% -48.6% causes reduced runoff. But when the pace of development cannot be suppressed or controlled, an effort to conserve groundwater is to create a groundwater infiltration medium. This groundwater infiltration medium can be in the form of yardland overgrown with grass vegetation or making rainwater infiltration wells. Both of these media are directly useful for collecting and absorbing rainwater into the soil. Thus groundwater recharge increases, and this increases the potential for groundwater availability.

Another groundwater conservation effort in this study is to reduce community behavior towards groundwater, which results in a 33% reduction in people's water needs. Positive community actions towards water are savings in water use, including the availability of water storage tanks, infiltration wells, and bathing/washing water facilities with good drainage from water disposal to reduce household waste.

Besides, efforts to implement groundwater conservation is reducing the level of groundwater pollution. In this study, decreasing groundwater pollution levels resulted in an increase in natural groundwater availability by 5.6% -15.6%. Providing outreach programs to the community by the central or local government is an effort to reduce groundwater pollution levels. This counselling informs to dispose of household liquid waste into sewerage to avoid pollution in water sources and avoid unpleasant odours. This counselling also provides knowledge about plastics, rubber, and cans that is can be recycling into more useful materials. Besides, this extension is to inform environmentally friendly land use.

Based on the analysis of the sustainable groundwater balance assessment using the relationship between water demand and population, land conversion, and its effect on groundwater availability in a residential area can be knowing in the status of the environment’s carrying capacity. In the analysis of groundwater balance assessments, several policy strategies are obtained to implement groundwater conservation policies, namely by implementing sustainable groundwater conservation programs, as shown in

Figure 12.

Finally, the dynamic system model approach can be applied to assess groundwater balance in an area both in Jakarta and other regions throughout Indonesia. This model is useful as a basis for simulating an area's groundwater conservation policy. The availability of groundwater in each region is very diverse and different. Hence, models can be adapted to each area's conditions (settlement, industry, or agriculture).

Acknowledgments.

The authors gratefully acknowledge the Central Statistics Agency (BPS) Jakarta, the

Ministry of Environment of the Republic of Indonesia, and the Ministry of Public Works,

Republic of Indonesia, who provided valuable literature and data for this paper. The authors also express their gratitude to the anonymous editors and reviewers for their insightful reviews and useful comments that have led to extensive improvements of the earlier version of this paper.

Data Availability Statement.

Some or all data, models, or codes generated or used during the study are available from the relevant authors by request. (The data about modelling results is available on the author and will be provided upon request. Not to be published).

Disclosure statement.

The author declares no conflicts of interest to disclose.

Funding.

The author gratefully acknowledges the Institute for the School of Environmental

Sciences - University of Indonesia, which has funded this article’s production through the

Doctoral International Indexed Publication Grant 2020. The author also thanks the

Pancasila University Institution, Jakarta, which has provided relevant scholarships.

ORCID iD:

Erna Savitri. https://orcid.org/0000-0002-2163-1034

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Fig. 1. Jakarta Province Map shows sampling locations in the study area

Fig. 2. The Third Causal Loop Diagram (CLD) Subsystem

community + behavior

+ hotel needs R +

Fig. 3. The Third Stock Flow Diagram (SFD) Subsystem.

Fig. 4. Population and water demand prediction.

Fig. 5. Simulation of structure validation of population and water demand.

Fig. 6. Simulation of performance validation of population and water demand.

Fig. 7. Simulation of structure validation against land conversion.

Fig. 8. Simulation of groundwater recharge as additional groundwater availability

Fig. 9. Simulation of groundwater balance prediction in the Kemayoran sub-district.

Fig. 10. Simulation of groundwater balance prediction in the Jagakarsa sub-district.

Fig. 11. Simulation of groundwater imbalance conditions.

Fig. 12. Sustainable groundwater conservation program.

That these drawings are to confirm the results of research on Click here to access/download;Figure;Figure Document.pdf assessing the sustainability of groundwater balance

Kemayoran sub-district

Jagakarsa sub-district

Fig. 1. DKI. Jakarta Map shows sampling locations in the study area.

community + behavior

hotel needs + R +

numbers + of hotel hotel water the water demand standard for polution + hotel water the standard + + needs percentage for population + of migration water needs + out migration Water demand out + domestic water demand + + + community + + + needs + + + + the behavior + IPA water IKA environmental birth toward R the total balance carrying capacity + B death of the region population groundwater + + Non domenstic - + + + water demand + percentage + percentage the standard for + of birth + of death + migration non domestic water + percentage population in needs decreased increased density of migration B groundwater R in the area of groundwater availability groundwater + developed availability availability + + land - + rasio of built evaporation land R rate area + + + + + land + + the pace of conversion + infrastructure evaporation development - + B + rainfall groundwater volume - rasio of open recharged + + land the area of open + rainfall land + + + Runoff

Fig. 2. The Third Causal Loop Diagram (CLD) Subsystem.

decreased increased groundwater groundwater birth rate death rate availability availabilty

migration in rate non domestik water demand percentage of birth percentage of death groundwater availability water pollution percentage migration in

built land built land existing coefiisien built land Cro built land rate built land

cumulative Cro open land coefisien area runoff rainfall groundwater open land Cro rainfall volume recharged

evaporation rate

The land conversion open land The groundwater availability the pace of open land rate subsystem as a natural subsystem as a built infrastucture environment model. environment model development evaporation Fig. 3. The Third Stock Flow Diagram (SFD) Subsystem.

Kemayoran sub-district Jagakarsa sub-district

year population (people) water demand (m³/year) year population (people) water demand (m³/year) 2,012 2,012 2,016 252,854 3,608,524 2,016 334,987 4,768,543 2,020 275,418 3,930,486 2,020 414,047 5,893,962 2,024 299,997 4,281,175 2,024 511,766 7,284,989 2,028 326,768 4,663,154 2,028 632,547 9,004,311 2,032 355,929 5,079,214 2,032 781,834 11,129,409 2,036 387,692 5,532,397 2,036 966,354 13,756,048 2,040 422,290 6,026,015 2,040 1,194,422 17,002,597 2,044 459,975 6,563,676 2,044 1,476,316 21,015,361 2,048 501,023 7,149,309 2,048 1,824,740 25,975,173 2,052 545,734 7,787,195 2,052 2,255,395 32,105,545 2,056 594,436 8,481,996 2,056 2,787,688 39,682,738 2,060 647,483 9,238,791 2,060 3,445,607 49,048,216 2,064 705,264 10,063,111 2,064 4,258,801 60,624,031 2,068 768,202 10,960,981 2,068 5,263,916 74,931,840 2,072 836,756 11,938,963 2,072 6,506,247 92,616,419 2,076 911,428 13,004,206 2,076 8,041,778 114,474,716 2,080 992,764 14,164,496 2,080 9,939,709 141,491,765

Fig. 4. Population and water demand prediction. Non-commercial use only! Non-commercial use only!

Kemayoran sub-district

people m³/year 12,000,000 800,000 11,000,000 9,000,000 700,000 6,000,000 600,000 9,000,000 3,000,000 500,000 7,000,000 0 400,000 2,013 2,025 2,037 2,049 2,061 2,073 population 5,000,000 300,000 water demand year 200,000 3,000,000 2,013 2,025 2,037 2,049 2,061 2,073 2,013 2,025 2,037 2,049 2,061 2,073 population (people) year year water demand (m³/year)

Jagakarsa sub-districtNon-commercial use only! Non-commercial use only! Non-commercial use only! people m³/year 130,000,000 9,500,000 130,000,000 100,000,000 8,000,000 110,000,000 70,000,000 6,500,000 90,000,000 40,000,000 5,000,000 70,000,000 10,000,000 3,500,000 50,000,000

population 2,013 2,028 2,043 2,058 2,073 2,000,000 30,000,000

water demand 500,000 10,000,000 year 2,013 2,028 2,043 2,058 2,073 2,013 2,028 2,043 2,058 2,073 population (people) year year water demand (m³/year) Non-commercial use only! Non-commercial use only! Non-commercial use only!

Fig. 5. Simulation of structure validation of population and water demand.

Kemayoran sub-district

75 690 600 70 685 500 680 65 400 675 60 300 670 55 200 665 100

built built land open land 50 660 0 45 655 2,013 2,025 2,037 2,049 2,061 2,073 40 650 2,013 2,025 2,037 2,049 2,061 2,073 2,013 2,025 2,037 2,049 2,061 2,073 year year year open land built land

Non-commercial use only! Non-commercial use only! Non-commercial use only! Jagakarsa sub-district

400 2,500 2,200 350 2,450 1,800 300 2,400 2,350 1,400 250 2,300 1,000 200 2,250 600

built land open land 150 2,200 200 100 2,150 2,013 2,025 2,037 2,049 2,061 2,073 50 2,100 2,013 2,025 2,037 2,049 2,061 2,073 2,013 2,025 2,037 2,049 2,061 2,073 year year year built land open land

Non-commercial use only! Non-commercial use only! Non-commercial use only!

Fig. 6. Simulation of structure validation against land conversion.

year water demand (m³/year) groundwater availability (m³) water balance (m³) IPA (%) IKA 2,061 9,438,314 11,828,789 2,390,475 79.79 1.25 5 2,062 9,642,146 11,703,771 2,061,625 82.38 1.21 2,063 9,850,380 11,580,122 1,729,742 85.06 1.18 2,064 10,063,111 11,457,829 1,394,718 87.83 1.14 2,065 10,280,436 11,336,879 1,056,443 90.68 1.10 2,066 10,502,455 11,217,258 714,803 93.63 1.07 2,067 10,729,269 11,098,951 369,683 96.67 1.03 2,068 10,960,981 10,981,945 20,964 99.81 1.00 2,069 11,197,697 10,866,225 -331,472 103.05 0.97 2,070 11,439,525 10,751,776 -687,750 106.40 0.94 2,071 11,686,577 10,638,584 -1,047,992 109.85 0.91 2,072 11,938,963 10,526,635 -1,412,328 113.42 0.88 2,073 12,196,800 10,415,915 -1,780,885 117.10 0.85 2,074 12,460,206 10,306,409 -2,153,797 120.90 0.83 2,075 12,729,300 10,198,104 -2,531,196 124.82 0.80 2,076 13,004,206 10,090,985 -2,913,221 128.87 0.78 2,077 13,285,049 9,985,039 -3,300,010 133.05 0.75 2,078 13,571,957 9,880,252 -3,691,705 137.36 0.73 2,079 13,865,061 9,776,611 -4,088,450 141.82 0.71 2,080 14,164,496 9,674,102 -4,490,393 146.42 0.68 6

Fig. 7. Simulation of groundwater balance prediction in the Kemayoran subNon-commercial-district. use only!

year water demand (m³/year) groundwater availability (m³) water balance (m³) IPA (%) IKA 2,061 51,716,439 68,027,954 16,311,515 76.02 1.32 5 2,062 54,529,813 66,031,921 11,502,108 82.58 1.21 2,063 57,496,235 64,086,633 6,590,397 89.72 1.11 2,064 60,624,031 62,191,755 1,567,725 97.48 1.03 2,065 63,921,978 60,346,831 -3,575,147 105.92 0.94 2,066 67,399,333 58,551,293 -8,848,041 115.11 0.87 2,067 71,065,857 56,804,485 -14,261,372 125.11 0.80 2,068 74,931,840 55,105,676 -19,826,164 135.98 0.74 2,069 79,008,132 53,454,067 -25,554,064 147.81 0.68 2,070 83,306,174 51,848,812 -31,457,362 160.67 0.62 2,071 87,838,030 50,289,018 -37,549,013 174.67 0.57 2,072 92,616,419 48,773,759 -43,842,660 189.89 0.53 2,073 97,654,752 47,302,086 -50,352,666 206.45 0.48 2,074 102,967,171 45,873,026 -57,094,144 224.46 0.45 2,075 108,568,585 44,485,597 -64,082,988 244.05 0.41 2,076 114,474,716 43,138,806 -71,335,910 265.36 0.38 2,077 120,702,140 41,831,656 -78,870,484 288.54 0.35 2,078 127,268,337 40,563,153 -86,705,184 313.75 0.32 2,079 134,191,734 39,332,303 -94,859,431 341.17 0.29 2,080 141,491,765 38,138,121 -103,353,643 371.00 0.27 6

Fig. 8. Simulation of groundwater balance prediction in the Jagakarsa subNon-commercial-district. use only!

Kemayoran sub-district Jagakarsa sub-district

m³ m³ 3,800,000 21,000,000 3,400,000 18,000,000

3,000,000 15,000,000 12,000,000 2,600,000 9,000,000

groundwater recharged groundwater recharged 2,200,000 6,000,000 1,800,000 3,000,000 2,013 2,025 2,037 2,049 2,061 2,073 2,013 2,025 2,037 2,049 2,061 2,073 year year

Non-commercial use only! Non-commercial use only!

Fig. 9. Simulation of groundwater recharge as additional groundwater availability.

Kemayoran sub-district Jagakarsa sub-district

m³ m³ 18,000,000 130,000,000 16,000,000 110,000,000 14,000,000 12,000,000 90,000,000 10,000,000 70,000,000 8,000,000 50,000,000 6,000,000 30,000,000 4,000,000 10,000,000 2,013 2,025 2,037 2,049 2,061 2,073 2,013 2,025 2,037 2,049 2,061 2,073 year year groundwater availability water demand groundwater availability water demand

Non-commercial use only! Non-commercial use only!

Fig. 10. Simulation of groundwater imbalance conditions.

Groundwater management concept

Feedback Groundwater protection and conservation Social Analysis of program environment groundwater Sustainable Maintaining the existence utilization Built Groundwater and continuity of environment Conservation groundwater availability Analysis of Model program groundwater natural damage environment Quality management and pollution control program

Fig. 11. Sustainable patterns of groundwater conservation.

Sustainable Groundwater Sustainability Actions Conservation Program 1. Maintain the aquifer carrying capacity Protection and 2. Restoring groundwater conditions and environment in preservation of critical zones groundwater 3. The importance of water needs for the present and future generations 1. Savings in groundwater usage 2. Control in the use of groundwater Maintain the existence 3. Increase water catchment capacity and continuity of 4. Attitudes and actions in protecting groundwater resources groundwater availability 5. The improvement of clean water services by PAM (piping) is targeted to be served 80%, according to 2017 SDGs. 1. Preventing groundwater pollution 2. Tackling groundwater pollution Quality management and 3. Restoring the quality of groundwater that has been polluted pollution control 4. Close any dug wells or drilled wells whose groundwater quality has been polluted.

Fig. 12. Sustainable groundwater conservation program.

Conflict of Interest

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☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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