Towards a sustainable city: planning the fulfilment of urban fresh water needs of Depok in both dry and rainy seasons

Management of water resources is a complex and challenging issue because it includes both hydrological and biological systems, as well as needs, values and problems related to human goals. The potential regional impacts of global environmental changes, such as climate change, can also pose significant challenges to users and managers of water resources (Bharati et al. 2008). Antunes et al. (2009) have said that the availability of water is an essential element in socio-economic development and the eradication of poverty.

These changes lead to annual increases in freshwater use and the need for freshwater from the collecting of rainwater, surface water (lakes, in situ and other sources) and groundwater. Rain is a source of water that may have been polluted before/as it falls to the surface of the earth and so cannot meet drinking water requirements (Brooks et al. 2012). Surface water is water from rivers, lake, dams and swamps that cannot be drunk directly because it also may be contaminated (Larocque & Broda 2016). Therefore, due to the lack of water treatment technology for producing freshwater from rain and surface water, people tend to use groundwater. The amount of groundwater available is not directly proportional to the number of large cities utilising groundwater as a source of fresh water. In addition, people tend to use deep groundwater because shallow groundwater is likely to contain pathogenic bacterial contamination from septic tanks (Ponsadailakshmi et al. 2018). Such practices have spread throughout urban populations.

The increase in urban populations is a major factor affecting demand for fresh water. As a result, urban water services need to be improved to meet the water needs of their populations. The growing need for fresh water influences the amount of water available. In addition, the building of urban water service capacity needs to be balanced with the availability of water within the urban area itself. Increased population growth, growth in economic activity and the pace of development lead to continued issues in terms of the availability of public water resulting from changes in land use. (Hossain & Bahauddin 2013). It is therefore essential that proper planning for the provision of fresh water for inhabitants should take place (Arfanuzzaman & Rahman 2017).

To identify the problems and challenges in urban water supply, water resources planning programmes are aimed at improving the coverage and capacity of services needed to meet urban demands and to supply the raw materials required for the provision of urban water (Karamouz et al. 2017). Efforts are made to prioritise rehabilitation activities and the operation and maintenance of natural water infrastructure, in order to restore and optimise the function of raw water infrastructure. Additionally, the construction of raw water infrastructure in the form of raw water containers and raw water carrier channels is also carried out to improve service capacity.

In terms of the issue of providing water, Indonesia has an abundant supply of water resources but faces limitations in providing fresh water for its citizens. Experts estimate that only 40% of all urban residents in Indonesia have access to piped water, with the rest relying on groundwater. An example of problems created by this situation is the water crisis experienced by Jakarta, which is the largest city in Indonesia. In 1997, only 42% of the population had access to piped water, with many still relying on groundwater run-off. Not only do these inhabitants experience unequal access to piped water connections but they also experience problems with water quality (Sedyowati et al. 2017). The availability of fresh water in urban areas faced with the threat of water scarcity results from developmental imbalances. Excessive exploitation of groundwater leads to water reduction and to saltwater intrusion. More efficient efforts in the management of available water resources are necessary, including implementing conservation and urban water consumption reduction programmes (Devitt & Morris 2010).

One region that faces this issue in Indonesia is Depok, which is located in a particularly strategic position. It is directly adjacent to the capital city of Indonesia, Jakarta, and this area is a centre of growth both for Java Island and for the country as a whole. The population of Depok is growing rapidly because of the migration of local population (circular migration) from outside Depok. This increase in the number of residents is accompanied by changes in land function from other uses to residential areas. This means that Depok is experiencing spatial problems and urban land management issues. The relatively high growth rate of Depok, followed by economic growth and the development of settlements, have caused high water use and increased water scarcity. Economic activities and settlements will result in polluted water sources due to poorly managed waste disposal. This means that the availability of fresh water that can be consumed by the population is declining. Currently, only 17.1% of the population of Depok buy fresh water from municipal waterworks, with the remainder obtaining their supplies from groundwater in the form of wells (Tempo.co 2018). This increasing use of groundwater is resulting in a decrease in land surface level of approximately 0.3 cm per year in Depok (Tempo.co 2018). Therefore, a plan is necessary for managing the provision of raw water for fresh water distribution to the community.

• = Population at year end (number of people)

• = Population at the beginning of the data year

• = Average population growth each year (%)

• = Time projection year

In this study, geometric methods are used in projecting the population. This is the best method to represent an increasing pattern of population growth. Depok has a pattern of rapid population growth over time due to the high rate of urbanisation. Projected population growth has a close relationship with water supply system planning in a region. The amount of fresh water needed in the future is determined based on development and increases in the population. Population data is used to determine the predicted growth of population at the end of the technical planning period of a pipeline network.

Socio-economic developments increase the basic demand for water and generate new habits and patterns for the consumption of fresh water (Bouayoune et al. 2017). Today, people need fresh water for a variety of activities, from eating and drinking to bathing, washing, toilets, and tertiary needs such aesthetic and recreational purposes (Karamouz et al. 2017; Lisiak et al. 2017). This is known as fresh water use for domestic needs.

However, the need for fresh water is not limited to domestic requirements; non-domestic demands are also growing. In terms of non-domestic needs, fresh water is used for various social activities that involve public facilities, as well as for commercial activities. As a result, freshwater requirements exceed the total availability of fresh water by 20% to 30%. (Panagopoulos et al. 2012). High use of water by a community is caused by several factors, such as the local economic activity level, standard of living, education level and social conditions. Therefore, in the planning of a system for the meeting of fresh water needs, the types of water use and local variation need to be taken into account (Noiva et al. 2016). The calculation of water demand in an area differs between dry and rainy seasons, calculated based on predefined water requirement classification standards. The primary factor for the calculation of water requirements is the size of population in the planning area.

Furthermore, formulation also differs based on seasonal factors and conditions, depending on freshwater needs both for domestic and non-domestic use. Therefore, in calculation and planning, assumptions or approaches based on the classification of seasonal characteristics within a city are needed (Bergel et al. 2017). Calculation of urban water needs can be carried out according to the estimation presented in Table 1. In this table, the 10% water loss stated is the average water loss in Indonesia as calculated by the Directorate General of Human Settlements section of the Ministry of Public Works of Indonesia.

Based on Table 1, the level of usage of fresh water in the dry season can be arrived at by calculating the fulfilment of daily fresh water needs. The analysis is done by gradual calculation for water supply planning. A similar calculation for the rainy season is shown in Table 2.

Based on Table 2, the level of usage of fresh water in the rainy season can be arrived at from the fulfilment of daily fresh water needs. The analysis is done using gradual calculation for water supply planning.

The use of water fluctuates over time, and, in general, people use most water in their activities in the morning and afternoon. The activities of the population, societal customs, customs of individual people and urban patterns affect the amount of fresh water used per hour, and this amount fluctuates. Maximum daily use and maximum hourly usage for the average daily need for fresh water are used to measure variations in water demand (Tiwari et al. 2016).

As stated, water requirement is determined based on the maximum daily water requirement (Qmax). In addition, the water requirement at peak times (Qpeak) establishes the total water requirement in combination with the average water requirement. The average daily water requirement (Qav) is determined by adding up the necessary water to meet both domestic and non-domestic water demand and water loss. The fluctuation factor in the calculation of the maximum daily water requirement (Qmax) is required so that the most amount of water needed on a single day within a year can be identified. This calculation is based on the daily average value, Q. Meanwhile, maximum water hour requirement (Qpeak) requires reference to fluctuations in the maximum time requirement (fpeak) in its calculation. Thus, the largest amount of water required at certain hours can be calculated (Bergel et al. 2017). In addition to the maximum daily water requirements and maximum water hour requirements, water loss is also one of the determinants of average water requirement. The loss of water is the difference in the amount of water produced by treatment units and the total water that has been distributed for consumption. Water loss can be both technical and non-technical in nature. It is categorised into three types: planned water loss, loss of free water and accidental water loss. Loss of free water and incidental water loss are included in the calculation of the value of the loss; the loss amount ranges from 15–20% of the total need for fresh water, both domestic and non-domestic (Panagopoulos et al. 2012).

Resolving the complex problems related to the fulfilment of water needs requires a holistic approach. The traditional fresh water management approach, which focuses solely on finding a new water source, has failed to solve current problems. A modern approach to freshwater management to meet community water needs is needed. In this approach, efforts should be made such as raising public awareness of the environment, controlling water use, improving or modifying new water sources and minimising conflicts among water management stakeholders (Himes 2007). Efforts should start with analysing the need for fresh water.

Based on the results of calculations performed, the need for fresh water in Depok every year increases along with the increase in population. In 2016, Depok's population reached 2,180,000 people, requiring 136,032,000 litres/second of fresh to meet domestic water demand in the dry season. This amount increases every year. By 2020, the amount of water required is likely to be 156,280,925 litres/second, and by 2030, the required water will be 221,089,502 litres/second. Furthermore, in the rainy season, the need for fresh water is even greater. This can be understood as being due to non-domestic water use, especially for agricultural practices. This water use consumes rainwater, for example, as irrigation water for crops. This is also calculated because rainwater naturally returns to the ground as usable groundwater or runs off to other water stores. As a result, in the rainy season, water consumption is higher.

In the same year, 2016, Depok needed 265,088,000 litres/second of fresh water in the rainy season to meet domestic water needs. The amount of water required will increase to 430,841,082 litres/second in 2030. Meanwhile, in fulfilling the requirements for non-domestic water such as social use and commercial facilities, Depok required 40,809,600 litres/second of water in 2016 in the dry season. The need for non-domestic water in the dry season also increases every year, and so in 2030 the amount of water required will be 66,326,851 litres/second. Based on Table 3, the total amount of fresh water needed in the dry season can be seen to increase in 2030 to 431,124,530 litres/second. Meanwhile, in the rainy season, the total demand for fresh water in 2016 is more than double the total demand for fresh water in the dry season in the same year, which amounted to 516,912,000 litres/second. Based on Table 4, this amount will increase in 2030 to 840,140,109 litres/second.

Moreover, in the dry season of 2016 the average daily requirement of Depok residents for fresh water was 3,070 litres/second. As the population increases as is projected, by 2030 the average daily need for fresh water in Depok will be 4,990 litres/second (Table 3). The same thing happens in the rainy season, with the average daily need for fresh water increasing every year. The average daily need for fresh water in 2016 of 5,983 litres/second will increase to 9,724 litres/second by 2030 (Table 4).

The calculation of the daily need for fresh water was multiplied by a factor of 1.25. The calculation results obtained in 2016 in the dry season were 3,838 litres/second. If projected, the maximum daily amount of fresh water demanded in 2030 increases to 6,237 litres/second. Meanwhile, in the rainy season, the maximum daily need for fresh water in 2016 was 5,373 litres/second and this increases to 8,732 litres/second when projected to 2030. The amount of fresh water needed by the people of Depok will increase if the calculation of freshwater needs is carried out at peak time. In 2016 in the dry season, the need for fresh water of Depok residents at peak hour is 5,373 litres/second. In 2030, the need for fresh water for Depok residents at peak hour is projected to increase to 8,732 litres/second. Meanwhile, the need for fresh water at peak hour in the rainy season in 2016 was 10,470 litres/second and is projected to increase to 17,017 litres/second in 2030. This amount is more than the need for fresh water at peak hour in the dry season.

This forecasting of the freshwater needs of the population by 2030 reflects the results of the calculation of projected urban population. The larger population will increase demand for freshwater, so the government must be ready to fulfil the need for fresh water of the population. Thus, review of the analysed calculation for freshwater requirements can be a consideration in planning the provision of fresh water (Friedman et al. 2014). Such a review should consider the characteristics of Depok itself.

Depok has an area of 200.3 square kilometres, 50% of which is designated as industrial areas, and 50% consists of green open space. However, in the areas of green open space, 30% to 40% is used as residential land. Hence, only 15 to 20% of the total water absorption area in Depok remains available. Several sub-districts are designated as water absorption areas, such as Cimanggis Sub-District, Sawangan District and Limo Sub-District. Determination of these three sub-districts has been put in place to maintain groundwater conservation in Depok. Previously, the area of water conservation in Depok was still very wide and utilised green cutting fields. However, since Depok became a large-scale national housing project (perumnas) in the mid-1970s, population growth has been generated. This makes open green land a part of residential areas. The development of residential areas, accompanied by the rapid development of infrastructure, has the effect of changing land use. It also has an impact on improving social, economic and cultural conditions. The growth of settlements will indirectly lead to an increase in the need for fresh water for supporting the activities of daily life.

Based on the analysis of the calculation results, the need for fresh water in Depok will continue to increase over time. The total fresh water required in Depok in the dry season in 2016 was 265,262,400 litres/second and this will increase to 431,124,530 litres/second in 2030, with the requirement at peak hour of 8,732 litre/second. The total requirement of fresh water in Depok in the rainy season of 2016 was more than double the total water demand in the dry season of the same year, at 516,912,000 litres/second. This amount increases to 840,140,109 litres/second in 2030, with peak hour demand of 17,017 litres/second. In response to these projections, the government of Depok should put in place effective planning for the provision of fresh water to meet the demands of city dwellers. Forecasting the freshwater needs of Depok is needed as a focus for water supply planning by the government. The availability of fresh water should be able to meet the demands of the population for domestic and non-domestic water needs (Vannevel 2016). From the results of forecasting the requirement for fresh water, planning its provision must be carried out at every season so that the freshwater needs of the people of Depok until 2030 can be fulfilled. This can be done in various ways, one of which is to improve the evaluation of fresh water production. In this way, the water supply system in Depok can be improved, and the fresh water needs of the population will be able to be fulfilled in the 2030 projection year. Additionally, if this plan can be well implemented, Depok will also become a role model for Indonesia in contributing towards the success of its Sustainable Development Goals (SDGs) (Mahgoub et al. 2010).

Fulfilment of water needs in relation to achieving the country's SDGs in 2030 should be conducted through two sectoral approaches, first through society and second through agencies (Nurbaiti & Bambang 2018). These two approaches should work together and be well coordinated to enable the provision of a suitable solution. In short, the solution involves government initiatives followed by supportive societal participation.

As a key factor in the success of any approach, society, especially in Depok, should be encouraged to create conducive conditions for achieving the solutions to the problems of water fulfilment. The conditions consist of the development of society's awareness of water conservation practices. Based on the social theory known as ‘social discourse’, integration of better water conservation practices should be internalised at three social structure levels: the micro-level, meso-level and macro-level (Hannigan 2006). A consistent internalisation throughout all levels will make good practice become part of cultural norms in the future. This process takes time but is not impossible if it is supported by local government in coordination with central government (in this case, Indonesia).

Although the fundamental factor is society, agencies, in this case governmental, should also play a vital part in solving the problem. In Depok, obligations and responsibilities to ensure the fulfilment of water needs are part of human rights commitments.

Depok contrasts with the case of Karimunjawa, which is a non-groundwater basin region (Rahayu & Soeprobowati 2018), and this makes it possible for groundwater to be exploited in the development of Depok. One of the centres of development is led by Universitas Indonesia, a leading university in Indonesia and the world, and is a central model for the development of surrounding areas. Its existence enhances the development of residential areas around it, including hotels and other developments. Residential areas, especially those run as profit-oriented businesses, often exploit groundwater to fulfil their water needs. The solution to problems which develop from such exploitation is to evaluate and optimise the management of piping water from reserves to residential areas. Massive drilling of ground water should be minimised under government regulations.

Of the two sectoral approaches, the main obstacles are centred in society. In general, society in Depok is not supportive in helping governmental agencies to manage water fulfilment. As a pillar in sustainable development, society demonstrates less care towards the environment than other actors. This fact is indicated by several negative practices around water cycles and management. One of those is the reducing of catchment areas resulting from housing development. Such development is very popular in Indonesia because of high levels of population increase and urbanisation, and is manifested by the loss of green open spaces. This practice then leads to many other relevant practices identified in terms of the sanitation of groundwater. As the main source of water for consumption, groundwater is often polluted by the mismanagement of septic tanks. Although these are placed at the right distance from people's own water wells, those of their neighbours are often not taken into account. This shocking practice has taken place in many housing developments for many years, leading to a dangerous accumulation of pollutants in daily water consumption. In light of such practices, coordinated and integrated water management will always be a challenge in terms of solving these obstacles.

Fresh water is a basic human need in maintaining survival. Fresh water is not only used in the fulfilment of domestic needs, but must also be available for non-domestic needs in supporting public and commercial facilities. Depok is an area that needs significant amounts of fresh water. In 2016, the people of Depok needed as much as 265,262,400 litres/second of fresh water during the dry season to meet the needs of the community, and in the rainy season, the amount of water needed increased to 516,912,000 litres/second. This calculation indicates the amount of domestic and non-domestic water required by Depok. Furthermore, the peak hours of fresh water use are in the morning and afternoon. The results of calculations obtained in 2016 show that the people of Depok use as much as 5,373 litres/second at peak times in the dry season, while in the rainy season, during peak hours as much as 10,470 litres/second in needed. This amount is predicted to increase along with the rapid rate of population growth in the area of Depok. If the calculation of the amount of fresh water is projected to 2030, the people of Depok will need up to 431,124,530 litres/second of fresh water during the dry season and 840,140,109 litres/second during the rainy season. At peak times, the people of Depok will need as much as 8,732 litres/second during the dry season and 17,017 litres/second during the rainy season. Solutions focus on two sectoral approaches, through society and agencies, although current conditions seem to present challenging obstacles.