Global water scarcity is aggravating with increasing urbanization and inappropriate urban water management. Implementing Circular Economy (CE) strategies in the water sector followed by their assessment can prove to be beneficial. Recently, the Water Circularity Indicator (WCI) has been developed to measure, monitor, improve and promote urban water circularity using the 5Rs (Reduce, Reuse, Recycle, Reclaim, Restore). Apprehending the role and scope of each strategy is crucial while planning future water infrastructure, as each strategy has inherent advantages and limitations in application. This study aims to facilitate decision-makers with an approach to prioritize 5Rs CE strategies, which will be helpful in the efficient allocation of funds and resources related to water infrastructure. A methodology is proposed to prioritize and weigh 5Rs based on the effort required to fulfill the application of each strategy. Using weights assigned to each R, WCI is improved to WCI-2.0 and is evaluated for the region under the jurisdiction of Pimpri-Chinchwad Municipal Corporation. The results from WCI-2.0 suggest which strategy to focus on out of the 5Rs to accelerate water circularity and effective infrastructure planning. Benchmarking of WCI-2.0 and its use to propose policies supporting urban water balance has the potential to change the prospects of the water sector.

  • A methodology to prioritize water circularity strategies is proposed.

  • Prioritizing Circular Economy (CE) strategies is essential.

  • Prioritization helps in the efficient allocation of funds and resources.

  • Water Circularity Indicator (WCI) is reformulated and improved.

  • WCI can be used for benchmarking and future infrastructure planning.

5Rs

Reduce, Reuse, Recycle, Reclaim, Restore

6Rs

Reduce, Reuse, Recycle, Reclaim, Restore, Recover

C

Total water consumed

CE

Circular Economy

CE - 1

CE Phase 1 (Scenario 4–2030)

CE - 2

CE Phase 2 (Scenario 6–2045)

CRc

Fraction of water collected for reclamation

CRe

Fraction of water collected for recycling

CRst

Fraction of water collected for restoration

CRu

Fraction of water collected for reuse

ERe

Usage efficiency in recycling

FRc

Fraction of water reclaimed from wastewater treatment facilities

FRe

Fraction of water recycled from wastewater treatment facilities

FRst

Fraction of water restored to the stock

FRu

Fraction of water reused

JJM-U

Jal Jeevan Mission (Urban)

L

Fraction of total volume of water lost

LFI

Linear flow index

MCI

Material circularity indicator

MLD

Million liters per day

NIP

National infrastructure pipeline

O&M

Operation and maintenance

PCMC

Pimpri-Chinchwad Municipal Corporation

R

any of the 5Rs strategies

Rst

Volume of water restored

S

Total water supplied

STP

Sewage treatment plant

V

Actual virgin water consumed

VC

Volume of virgin water consumed

W

Total volume of water discharged and released outside the system boundary

W0

Volume of untreated water generated

WCI

Water circularity indicator

WCI-2.0

Improved WCI

WRc

Volume of water wasted in reclamation

WRe

Volume of water wasted in recycling

WRst

Volume of water wasted in restoration

Urbanization coupled with inefficiencies in urban water management (UWM) have impacted the availability of freshwater resources (Falkenmark & Widstrand, 1992). A significant gap exists between the total water available and the water demanded, contributing to global water scarcity (He et al., 2021). Inappropriate water management practices, such as excessive virgin water consumption and untreated wastewater disposal, have resulted in an imbalance in the urban water cycle. Recirculation within the urban water cycle is one of the options to move toward self-sufficiency in cities and has been found to be beneficial (Rygaard et al., 2011). There is a need to balance the urban water cycle such that water entering into the city and going out of the city reduces with time through internal recirculation, which is in accordance with the principles of Circular Economy (CE) (Dolgen & Alpaslan, 2023). Thus, the concept of CE in the water sector is gaining increased attention to tackle the current global water crisis (Salminen et al., 2022).

To implement CE principles such as ‘closed loop supply chain, value retention, waste minimization and resource efficiency’ (Morseletto et al., 2022), it is essential to know the strategies or action plans that can help manage and balance the overall water resources (Miranda et al., 2022). Several strategies have been suggested in the literature to achieve the implementation of CE principles in the water sector. Kakwani & Kalbar (2020) proposed a framework incorporating 6Rs strategies namely Reduce, Reuse, Recycle, Reclaim, Recover and Restore to achieve circularity in the urban water sector. Concurrently, Smol et al. (2020) proposed a model CE framework using actions namely Reduce, Reuse, Recycle, Reclaim, Recover and Rethink in the water sector based on a waste management hierarchy. Later, Morseletto et al. (2022) provided nine CE strategies namely ‘Rethink, Avoid, Reduce, Replace, Reuse, Recycle, Cascade, Store and Recover’, indicating that the strategies are not restricted to R terms and can be extended to other terms such as Avoid, Cascade and Store. Moreover, Ruiz-Ocampo et al. (2023) proposed an additional strategy, i.e., Reconnect, a crucial action suggesting the use of digital technologies to achieve circularity in the water sector. Strategies or actions ultimately aim to implement circularity principles; however, the terms ‘Principles’ and ‘Strategies’ are used interchangeably (Uvarova et al., 2023) and the rigor in defining these terms is needed. To ensure clarity, the present study is grounded in the principles presented by Morseletto et al. (2022) and 6Rs strategies put forth by Kakwani & Kalbar (2020). These strategies serve as a comprehensive framework, as they encapsulate all the approaches or strategies mentioned above to achieve CE in the water sector. Implementing the 6Rs strategies ensures efficient use and recirculation of water within the system boundary, eventually contributing to water conservation. The application of any intervention steers with the need to monitor and assess its impact on the overall system. Thus, indicators are required to measure the level of circularity achieved after applying CE strategies.

Several frameworks have been proposed to derive indicators, emphasizing the need to provide a systematic and holistic assessment of CE (Nika et al., 2020a; Afghani et al., 2022; Rambau et al., 2022). Although indicators such as circular water footprint incorporating both direct and indirect water flows have been proposed to be viable for assessing circularity using natural and anthropogenic water flows (Sauvé et al., 2021), which can seldom be used. Moreover, the water mass balance of anthropogenic flows using material flow analysis (MFA) for water and wastewater flows can provide quantifiable outcomes for planning and policy initiatives (Arora et al., 2022; Kakwani & Kalbar, 2022). Further, multi-sectoral linkages incorporating energy and material with water contribute to efficient evaluation (Stanchev et al., 2017; Nika et al., 2020b).

Several frameworks and indicators have also been developed for urban water systems through approaches such as urban metabolism (Renouf et al., 2017, 2018), simulation or modeling tools (Makropoulos & Rozos, 2011; Peña-Guzmán et al., 2017), water security assessment (Zhu & Chang, 2020), and city blueprints (van Leeuwen et al., 2012) where one or multiple Rs are used for evaluation. While various indicators have been developed for urban water balance, there is a lack of consensus on their universal acceptance (Nika et al., 2021). Additionally, the existing indicators do not provide guidance on the order in which the R strategies can be prioritized and focused. Finally, the circularity of a water system so far has not been measured through a single indicator value.

For these reasons, a novel ‘Water Circularity Indicator (WCI)’ has been developed to promote, improve, monitor and manage water systems (Kakwani & Kalbar, 2022). The WCI is developed using 5Rs (Reduce, Reuse, Recycle, Reclaim and Restore) excluding Recovery because it did not consider material or energy extraction. Precisely, WCI relies on the water mass balance of engineered urban water systems. One of the limitations of WCI and the existing indicators is that they give equal weightage to all the strategies; however, each strategy or R requires a distinct level of effort during implementation, which is also highlighted in the frameworks proposed by Smol et al. (2020) and Rambau et al. (2022). The CE strategies are ordered, ranked, or prioritized from most desirable to least recommended considering the waste management hierarchy (Smol et al., 2020; Rambau et al., 2022). It is noteworthy to mention that the waste management hierarchy concentrates on waste, and not specifically water, but historically, it was the first framework to prioritize waste, and so it is used as a reference for the CE in the water sector.

Nevertheless, the approach to monitor or measure the application of such frameworks has not been developed so far. Similarly, Modak (2021) proposed the concept of the Bull's eye in prioritizing CE strategies starting with Prevention, i.e. Reduce, followed by Reuse, Recycle in inner circles and so on, with Disposal as the last priority in the outer circle. The concept proposed by Modak (2021) is based on a generalized CE application, not specific to the water sector. Thus, there is a need to prioritize and order strategies for CE implementation in the water sector. The current study aims to provide a methodology for prioritization of the 5Rs strategies of CE for the assessment of WCI and accordingly improve its impact. The methodology proposed can direct decision-makers toward efficient resource and fund allocation for future water infrastructure development. The 5Rs used in the WCI are prioritized and weighted for a typical city in India, followed by the formulation of improved WCI, hereafter referred to as WCI-2.0. The weightage process helps to indicate the priority of the concerned strategy, which depends on the region under consideration. Thus, weights assigned to each R are based on the effort required to fulfill its application in the Indian context.

In the present study, WCI-2.0 is applied to a typical city in India which can also be adapted for other regions based on region-specific strategy prioritization and weights. In essence, WCI-2.0 provides information about which strategy to focus on out of the 5Rs to accelerate the water circularity of the region under consideration. WCI-2.0 is then compared with WCI to express the importance of prioritization and weightage, followed by policy implications that can be drawn with the help of WCI-2.0.

The article has been divided into six sections. Section 2 discusses prioritization, why it is needed and how it can be carried out. Further, the research methodology is presented in Section 3, covering the formulation of WCI-2.0 and the study area selected with a detailed discussion of scenarios. Section 4 includes the results, followed by a discussion in Section 5 and finally, the conclusion in Section 6.

Typically, the engineered urban water cycle involves the abstraction of water, its treatment, supply and distribution, followed by consumption, conveyance of wastewater, wastewater treatment and finally, its disposal back into the water environment. Long-term strategic infrastructure planning is essential at each stage of the urban water cycle in transitioning from a water supply city to a water-wise city (Brown et al., 2009). Decision-makers play an instrumental role in city planning and infrastructure development. Guiding decision-makers with a prioritization framework for infrastructural investments can provide beneficial outcomes (Grimaldi et al., 2020). The priority order of the interventions varies from region to region based on the existing infrastructure, followed by future requirements and constraints.

In the current paradigm of UWM, incorporating localized solutions, life cycle thinking, and application of CE strategies has become essential to achieve sustainability (McDonald et al., 2014; Capodaglio et al., 2016). However, in India, the focus on the UWM is slightly skewed toward creating large-scale physical infrastructure for water and sanitation and the aspect of life cycle thinking while planning water management strategies is often ignored (Kalbar & Lokhande, 2023). Significant infrastructural investments materializing in India are based on the fulfillment of Sustainable Development Goals (SDG) targets 6.1 and 6.2, i.e., focusing on access to water and sanitation (TIE, 2023a) which occupy the third most significant position in the National Infrastructure Pipeline (NIP) projects, with water treatment projects being the second largest area of investment (NIP, 2020). Water demand is increasing rapidly due to urbanization, with key infrastructural investments being directed toward acquiring newer raw water sources located far from the city. Consecutively, in sanitation, the focus is on the construction of toilets and their access, neglecting the importance of sewage treatment plants (STPs) (Kalbar & Lokhande, 2023). Even if STPs are constructed, there is a lack of connectivity through the sewerage network (CPCB, 2021). Additionally, where wastewater is treated to the tertiary level, there is an absence of a market to use recycled water (Kalbar, 2021). Therefore, the water sector in India lacks a holistic approach in terms of infrastructure planning, design, and implementation, with priority given to centralized systems in water and wastewater management. Centralized systems require larger space and resources, leading to heavy investments compared to decentralized systems, which involve inherent complexity (Makropoulos & Butler, 2010; Sharma et al., 2010; Risch et al., 2021). Thus, there is a need to strategically plan future infrastructure considering the geographical and financial aspects of the region under consideration (Tsagarakis, 2013; Eggimann et al., 2015; Sood et al., 2023).

Further, infrastructure development is generally coupled with limited financial resources wherein the utility needs to prioritize strategies for efficient fund and resource allocation. At each stage of the urban water cycle, it is crucial to decide which of the 5Rs strategy can contribute toward efficient UWM. Presently, there is no such guidance available for the decision-making process. Hence, there is an immediate need for a methodology for the prioritization of CE strategies so that decision-makers can utilize it for future infrastructure development processes. The following two sub-sections provide details about the processes of prioritization and weights assigned to each strategy.

Prioritization of strategies

WCI gives equal weightage to all the 5Rs strategies; however, each R has inherent advantages and limitations in its implementation, which are utilized in prioritizing each R for execution in real-life situations and use in WCI-2.0. Modak (2021) proposed the concept of the outer circle, inner circle and bull's eye in applying CE strategies (refer to Figure 1). Smol et al. (2020) and Rambau et al. (2022) also proposed a framework based on a waste management hierarchy to order the CE strategies from most desirable to least recommended for the water sector. However, the strategies and their role slightly differ in role and scope compared to the current study. Thus, the essence from the above-stated studies is utilized to prioritize 5Rs used in WCI to develop WCI-2.0. For the present study, Reduce is the priority strategy, followed by Reuse, Recycle, Reclaim and Restore as shown in Figure 1.
Fig. 1

Prioritization of circular economy strategies for urban water sector.

Fig. 1

Prioritization of circular economy strategies for urban water sector.

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Fig. 2

Research methodology with steps carried out in the current study.

Fig. 2

Research methodology with steps carried out in the current study.

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The definition of all the strategies, along with their role and contribution to the water sector, is briefly explained in Section 1 of Supplementary Information -01 (SI-01). Reduce is the priority strategy as it directly curtails freshwater consumption. Restore is the last priority strategy as treatment and disposal are common practices in India; and compliance with water quality standards might not be ensured due to a lack of monitoring systems, leading to the pollution of water bodies (TOI, 2023). Hence, Reduce strategy is the priority followed by Reuse, Recycle, Reclamation strategies and Restore is the last priority strategy. Prioritization eventually depends on the region's water availability and management scenario. In the current study, WCI is utilized and improved by incorporating weights to represent the contribution of prioritization. The weights are identified to delineate the strategy prioritization in the WCI equation and are discussed in detail in the following section.

Weighting of CE strategies

Weights are allocated based on the priority order of each strategy, and in the present study, weights are decided based on the existing situation of the water sector in India. As this process is the first time carried out for the water sector, the weights are assigned based on authors' experience, understanding and also interaction with the field experts. The weights are provided to replicate the water circularity situation of a city or region under consideration which can also be changed based on the water sector situation for the city or region being studied. A particular strategy can be penalized based on its implementation challenges or rewarded based on its benefits using weights.

In the current study, weights are based on the effort required to fulfill a particular strategy. The effort is a cost criterion and has been applied in the form of its penalizing effect on all the 5Rs. Higher weight is assigned to higher effort and is applied as a penalty (1-Weight) to a particular R, thereby weakening the value of concerned R. Conversely, lower weight is assigned to lower effort, thereby strengthening the value of concerned R.

Four criteria are utilized to materialize weights for each strategy: Infrastructural requirement, Need for operation and maintenance (O&M), Stakeholders and their contribution, and Scale and extent of applicability. These criteria are selected in response to the water consumption status of a typical city in India. A brief explanation of each R for all the specified criteria, along with the implementation priority and weight assigned, are given in Table 1.

Table 1

Implementation priority and weights assigned to each strategy for the selected criteria for a typical city in India.

Implementation priorityStrategyInfrastructural requirementNeed for operation and maintenance (O&M)Stakeholders and their contributionScale and extent of applicabilityaWeight or effort
1 Reduce Minimal infrastructural requirements such as changes in fixtures or using water-efficient devices (dishwashers and washing machines). Since the installation of devices is feasible even on a small scale, the overall need for the infrastructure will be minimal. Timely maintenance of water supply and distribution infrastructure can extensively reduce water loss. The operation of appliances that are water-efficient and their maintenance can help in the reduction of freshwater consumption and wastewater generation. Overall, comparatively less O&M is required in Reduce strategy. The contribution of stakeholders from water utilities to take immediate action toward leakages and water losses is needed to enhance the implementation of Reduce strategy. Policy-makers can play a crucial role in promoting policies to use water-efficient devices. Further, the role of suppliers or NGOs in providing water-efficient fixtures at lower cost and the bulk supply can be significant. Ultimately, even small-scale applications, i.e. by the consumer/citizens, will contribute toward Reduce strategy. Reduce strategy can be made applicable even on a small-scale (household or industry level) by consumers. The extent of applicability may range from small, medium or large scale depending on the underlying purpose. 0.05 
2 Reuse Limited modification in the infrastructure is required, for example, diverting used water toward the location of reuse. The infrastructural requirement varies based on the type and location of the reuse process. Since water reuse takes place locally, the overall need for infrastructure will be considerably low. O&M of the infrastructure for redistribution of the used water is required, followed by the maintenance of the storage and infrastructure connected to the consumption of used water. Comparatively, more O&M is needed in the Reuse strategy. The introduction of policies to enhance local-level reuse, wherever feasible, by providing subsidies can enhance reuse. The industry's role in manufacturing eco-friendly products such as detergents, soaps and other chemicals is significant to ensure safe reuse. The consumer also has to make efforts to practice water reuse instead of using virgin water. Comparatively, a greater number of stakeholders are required in the Reuse strategy. Reuse strategy involves localized scale implementation, such as consumer or community level. Thus, reuse is applicable from small to medium (community) scale. 0.10 
3 Recycle Moderate infrastructural requirements, including localized treatment facility along with conveyance toward the utilization location. Since recycled water consumption generally happens locally, the conveyance infrastructure required will be moderate. O&M of conveyance and treatment infrastructure at a localized scale is needed. Also, the O&M of infrastructure related to the redistribution of recycled water is needed. Hence, greater O&M is required in the Recycle strategy compared to the Reuse strategy. Recycling involves utility stakeholders to encourage recycling by introducing policies. The subsidy can be provided to the implementer as a token of appreciation. Stakeholders involved in the O&M of Recycling facility are needed. Thus, the Recycle strategy demands a higher number of stakeholders compared to Reuse strategy. Recycle strategy involves treatment and consumption at a consumer or community level. Thus, recycling is applicable from small (building or industry) to medium (community) scale. 0.15 
4 Reclaim Significant infrastructural changes are required, such as semi-centralized or centralized treatment facilities followed by conveyance. The treatment technology is decided based on the end-use considering quality and quantity aspects; accordingly, the treated wastewater is conveyed either with the help of underground pipelines or tankers. Thus, large-scale infrastructural changes are required for reclamation. O&M of the conveyance and treatment infrastructure is needed for the semi-centralized or centralized scale of reclamation facilities. Also, maintenance of storage and redistribution infrastructure is essential. Hence, a higher level of O&M is required for the Reclaim strategy compared to Recycle strategy. Reclamation involves diverse stakeholders such as policy-makers, industries, public utilities, buyers and technology providers. Awareness generation and outreach programmes would play a significant role in facilitating the collaboration of multiple stakeholders to accomplish the Reclaim strategy. Large number of stakeholders are required to accomplish Reclaim strategy. Reclamation involves treatment and consumption by diverse stakeholders at a semi-centralized (community) or centralized (city) scale. Thus, reclamation is applicable from medium (community) to large (city) scale. 0.20 
5 Restore Extensive infrastructure is required in centralized or decentralized wastewater treatment facilities. The treated wastewater is conveyed and disposed of into the natural environment for restoration. Infrastructure is further required to abstract and convey the restored water. Hence, restoration leads to an extensive infrastructural requirement. Extensive O&M is required for conveyance and treatment infrastructure, followed by monitoring as per disposal standards. O&M is also needed for the safe disposal of treated wastewater. Furthermore, O&M is essential to abstract, supply, treat and distribute the restored water. Eventually, major O&M of the infrastructure is needed in Restore strategy. Restoration involves many stakeholders, including public utilities, monitoring agencies and policy-makers, to resort to restoration. Stakeholders related to treatment and safe disposal of wastewater, including technology providers. Further, stakeholders involved in treatment and supply of restored water. Thus, the major number of stakeholders across all the stages of consumption is required in the Restore strategy. Restore strategy can be applied at any scale, from small to large scale; yet, the point of attention is that the effort applied in restoration does not directly reduce the virgin water demand. 0.50 
Implementation priorityStrategyInfrastructural requirementNeed for operation and maintenance (O&M)Stakeholders and their contributionScale and extent of applicabilityaWeight or effort
1 Reduce Minimal infrastructural requirements such as changes in fixtures or using water-efficient devices (dishwashers and washing machines). Since the installation of devices is feasible even on a small scale, the overall need for the infrastructure will be minimal. Timely maintenance of water supply and distribution infrastructure can extensively reduce water loss. The operation of appliances that are water-efficient and their maintenance can help in the reduction of freshwater consumption and wastewater generation. Overall, comparatively less O&M is required in Reduce strategy. The contribution of stakeholders from water utilities to take immediate action toward leakages and water losses is needed to enhance the implementation of Reduce strategy. Policy-makers can play a crucial role in promoting policies to use water-efficient devices. Further, the role of suppliers or NGOs in providing water-efficient fixtures at lower cost and the bulk supply can be significant. Ultimately, even small-scale applications, i.e. by the consumer/citizens, will contribute toward Reduce strategy. Reduce strategy can be made applicable even on a small-scale (household or industry level) by consumers. The extent of applicability may range from small, medium or large scale depending on the underlying purpose. 0.05 
2 Reuse Limited modification in the infrastructure is required, for example, diverting used water toward the location of reuse. The infrastructural requirement varies based on the type and location of the reuse process. Since water reuse takes place locally, the overall need for infrastructure will be considerably low. O&M of the infrastructure for redistribution of the used water is required, followed by the maintenance of the storage and infrastructure connected to the consumption of used water. Comparatively, more O&M is needed in the Reuse strategy. The introduction of policies to enhance local-level reuse, wherever feasible, by providing subsidies can enhance reuse. The industry's role in manufacturing eco-friendly products such as detergents, soaps and other chemicals is significant to ensure safe reuse. The consumer also has to make efforts to practice water reuse instead of using virgin water. Comparatively, a greater number of stakeholders are required in the Reuse strategy. Reuse strategy involves localized scale implementation, such as consumer or community level. Thus, reuse is applicable from small to medium (community) scale. 0.10 
3 Recycle Moderate infrastructural requirements, including localized treatment facility along with conveyance toward the utilization location. Since recycled water consumption generally happens locally, the conveyance infrastructure required will be moderate. O&M of conveyance and treatment infrastructure at a localized scale is needed. Also, the O&M of infrastructure related to the redistribution of recycled water is needed. Hence, greater O&M is required in the Recycle strategy compared to the Reuse strategy. Recycling involves utility stakeholders to encourage recycling by introducing policies. The subsidy can be provided to the implementer as a token of appreciation. Stakeholders involved in the O&M of Recycling facility are needed. Thus, the Recycle strategy demands a higher number of stakeholders compared to Reuse strategy. Recycle strategy involves treatment and consumption at a consumer or community level. Thus, recycling is applicable from small (building or industry) to medium (community) scale. 0.15 
4 Reclaim Significant infrastructural changes are required, such as semi-centralized or centralized treatment facilities followed by conveyance. The treatment technology is decided based on the end-use considering quality and quantity aspects; accordingly, the treated wastewater is conveyed either with the help of underground pipelines or tankers. Thus, large-scale infrastructural changes are required for reclamation. O&M of the conveyance and treatment infrastructure is needed for the semi-centralized or centralized scale of reclamation facilities. Also, maintenance of storage and redistribution infrastructure is essential. Hence, a higher level of O&M is required for the Reclaim strategy compared to Recycle strategy. Reclamation involves diverse stakeholders such as policy-makers, industries, public utilities, buyers and technology providers. Awareness generation and outreach programmes would play a significant role in facilitating the collaboration of multiple stakeholders to accomplish the Reclaim strategy. Large number of stakeholders are required to accomplish Reclaim strategy. Reclamation involves treatment and consumption by diverse stakeholders at a semi-centralized (community) or centralized (city) scale. Thus, reclamation is applicable from medium (community) to large (city) scale. 0.20 
5 Restore Extensive infrastructure is required in centralized or decentralized wastewater treatment facilities. The treated wastewater is conveyed and disposed of into the natural environment for restoration. Infrastructure is further required to abstract and convey the restored water. Hence, restoration leads to an extensive infrastructural requirement. Extensive O&M is required for conveyance and treatment infrastructure, followed by monitoring as per disposal standards. O&M is also needed for the safe disposal of treated wastewater. Furthermore, O&M is essential to abstract, supply, treat and distribute the restored water. Eventually, major O&M of the infrastructure is needed in Restore strategy. Restoration involves many stakeholders, including public utilities, monitoring agencies and policy-makers, to resort to restoration. Stakeholders related to treatment and safe disposal of wastewater, including technology providers. Further, stakeholders involved in treatment and supply of restored water. Thus, the major number of stakeholders across all the stages of consumption is required in the Restore strategy. Restore strategy can be applied at any scale, from small to large scale; yet, the point of attention is that the effort applied in restoration does not directly reduce the virgin water demand. 0.50 

aWeight is applied as a penalty, i.e. (1-Weight).

Thus, this section describes the need for prioritization of CE strategies wherein Reduce is the priority strategy and Restore is the least priority strategy. Since the Reduce strategy requires the lowest effort in implementation, it acquires the least weight (0.05), followed by Reuse (0.1), Recycle (0.15) and Reclaim (0.2). Restore strategy acquires the highest weight (0.5) as it requires the highest effort on implementation as compared to all the strategies.

The methodology to present the impact of prioritization and weights discussed in the previous sections is elucidated in this section. The formulation of WCI-2.0 using priority weights is given in the section. WCI-2.0 is then applied to a city in India and evaluated for six scenarios discussed in the following sub-sections. Figure 2 shows the methodology and steps carried out in this study.

Improved water circularity indicator (WCI-2.0)

Assigning implementation priority and weights to each R can change the overall outlook of the water sector in the city or region under consideration. WCI-2.0 can provide valuable insights about the direction in which efforts can be invested by utility managers, planners or investment authorities. A detailed derivation of WCI and its parameters is provided by Kakwani & Kalbar (2022). In the current study, the WCI is reformulated to incorporate weights. Firstly, it is crucial to understand that WCI is ultimately the sum of fractions of water reused, recycled, reclaimed and restored, i.e. FRu, FRe, FRc, FRst, respectively, and excludes the fraction of water reduced (FRd). A derivation for the same is provided using Equations (7), (16) and (18)
formula
(1)
formula
(2)
Using Equations (1) and (2)
formula
(3)
formula
(4)
formula
(5)
Using Equations (4) and (5)
formula
formula
(6)
formula
(7)
formula
(8)
formula
(9)
Using Equations (8) and (9)
formula
(10)
OR
formula
formula
(11)
formula
formula
formula
(12)
Similarly,
formula
(13)
formula
(14)
Using Equations (12)–(14) in Equation (10)
formula
(15)
Or
formula
formula
(16)
Equation (3) can also be written as
formula
Using Equations (7) and (16)
formula
Or
formula
Since,
formula
formula
(17)
Therefore,
formula
(18)

As explained by Kakwani & Kalbar (2022), the fraction of water reduced is accounted for outside the system boundary, and its impact on WCI is not directly visible. However, Reduce is the priority strategy, and its role in the evaluation of WCI is essential. Thus, to incorporate the volume of water reduced, FRd is added to the sum of all the other Rs obtained in Equation (18).

To evaluate the WCI-2.0, each fraction of 5Rs is penalized based on the effort by multiplying it with (1-Weight), as discussed in Section 2.2. The WCI is reformulated as WCI-2.0 by incorporating the weights of all the Rs. Suppose a, b, c, d and e are the weights assigned to the fraction of water reduced, reused, recycled, reclaimed and restored, respectively; then the WCI-2.0 is calculated using the following equation:
formula
(19)
where WCI-2.0, Improved WCI based on weights assigned; FRd, Fraction of water consumption reduced; FRu, Fraction of water reused; FRe, Fraction of water recycled from wastewater treatment facilities; FRc, Fraction of water reclaimed from wastewater treatment facilities; FRst, Fraction of water restored to the stock; a –weight as an effort for FRd (0.05); b, weight as an effort for FRu (0.10); c, weight as an effort for FRe (0.15); d, weight as an effort for FRc (0.20); e, weight as an effort for FRst (0.50).

Hence, the WCI-2.0 value incorporates the impact of all 5Rs, including Reduce strategy, along with the weights of each strategy in the form of a penalty to the respective strategy. It is essential to note that the WCI-2.0 value is different from WCI in terms of weightage and water consumption reduction. WCI-2.0 thus provides an opportunity to plan future strategies considering the priority, thereby improving the urban water circularity. The following section demonstrates the variation in values of WCI and WCI-2.0 for a case study, thus indicating the importance of prioritizing circularity strategies.

Case study

Pimpri-Chinchwad city in the Pune district of Maharashtra state in India (refer Figure 3) is selected as a case study area to demonstrate the impact of WCI-2.0 and its variation with WCI. It is spread over an area of around 180 km2 and is divided into eight zones and 32 wards (PCMC ESR, 2022). The city comprises the twin towns of Pimpri and Chinchwad, which are governed by a common municipal body named Pimpri-Chinchwad Municipal Corporation (PCMC). Pimpri-Chinchwad is one of the fastest-urbanizing cities in India. It is a major industrial center of the country, accommodating small and medium enterprises, prominent automobile, pharmaceutical, and many other national and multinational companies. Each year, the landscape has significantly changed, with long stretches of farmland converted to enclosed factory campuses. Thus, with changes in the city landscape, changes in resource consumption have also been observed (PCMC ESR, 2022). Further, the population of the city is rising significantly, leading to an increase in water demand. Consequently, the city is experiencing a water shortage (TIE, 2023b), and the corporation is working toward achieving water circularity (PCMC, 2020). Hence, for the present study, the PCMC region is selected as a case study for evaluating water circularity.
Fig. 3

Pimpri-Chinchwad city in the Pune district of Maharashtra to demonstrate the impact of WCI-2.0 and its variation with WCI. (PCMC – Pimpri-Chinchwad Municipal Corporation).

Fig. 3

Pimpri-Chinchwad city in the Pune district of Maharashtra to demonstrate the impact of WCI-2.0 and its variation with WCI. (PCMC – Pimpri-Chinchwad Municipal Corporation).

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The city's population in 2022 was around 2.5 million, with a water supply of about 535 MLD, i.e., 535,000 m3/day (million liters per day (1 MLD = 1000 m3/d)) (PCMC ESR, 2022). PCMC is working toward converting the current water supply system from intermittent to continuous (PCMC, 2016) and a new water treatment plant of 100 MLD capacity is planned to operate at Chikhali in the near future (PCMC ESR, 2022).

The current STP capacity is 353 MLD, out of which 280 MLD of sewage is treated up to the secondary level and around 19 MLD of reclaimed water is used for industrial purposes (CPCB, 2021). PCMC authorities are in the process of upgrading the current secondary treatment infrastructure to a tertiary level for 100 MLD capacity spread across five locations (PCMC ESR, 2022). As per the discussion with PCMC officials, the treated sewage will be sold to industries at a 30% reduced cost. PCMC plans an additional 32 MLD STP under a national-level AMRUT (Atal Mission for Rejuvenation and Urban Transformation) scheme (PCMC ESR, 2022). Furthermore, 22 MLD capacity STP is under construction, which will partially contribute to river restoration (PCMC ESR, 2022).

After understanding the water supply and wastewater treatment situation, six scenarios are developed to assess and understand the potential of PCMC to promote circularity (refer Table 2). The first scenario includes the status of PCMC in 2022 (S1), followed by PCMC plans for the year 2030 (S2). Recently, the Government of India has been promoting CE in the water sector through the ambitious Jal Jeevan Mission (Urban) (JJM-U) to be accomplished by 2030 (JJM-U, 2021). Thus, the third scenario is developed as per JJM-U recommendations for 2030 (S3). The fourth scenario is proposed considering the land use and future growth by estimating the city's potential to 5Rs strategies and achieve CE in future, named as CE Phase 1 for 2030 (S4). The last two scenarios are for the year 2045, S5 is as per PCMC plans for 2045 and S6 is as per potential for CE, i.e. CE Phase 2 in 2045 (refer Table 2).

Table 2

Input variables for the evaluation of the water circularity indicator based on six scenarios generated for the Pimpri-Chinchwad Municipal Corporation (PCMC) region as per PCMC plans, Jal Jeevan Mission (Urban) and CE Phase 1 and 2.

Input variablesScenarioS1S2S3S4S5S6
PCMC 2022 PCMC 2030JJM-U 2030CE-1 2030PCMC 2045CE-2 2045
Demand (MLD) 553.65 695 695 965 1,044 1,044 
Total water supplieda S(MLD) 553.65 695.00 695.00 695.00 1,044.00 1,044.00 
Total water consumed C(MLD) 553.65 681.37 661.90 643.52 1,003.85 949.09 
Fraction of water consumption reduced FRd 0.00 0.02 0.05 0.08 0.04 0.10 
Fraction of water reused FRu 0.00 0.00 0.00 0.06 0.00 0.10 
Fraction of water recycled from wastewater treatment facilities FRe 0.00 0.05 0.10 0.10 0.07 0.10 
Fraction of water reclaimed from wastewater treatment facilities FRc 0.03 0.17 0.18 0.18 0.12 0.17 
Fraction of water restored to the stock FRst 0.47 0.44 0.49 0.54 0.32 0.53 
Fraction of total volume of water lost L 0.20 0.18 0.15 0.12 0.16 0.10 
Input variablesScenarioS1S2S3S4S5S6
PCMC 2022 PCMC 2030JJM-U 2030CE-1 2030PCMC 2045CE-2 2045
Demand (MLD) 553.65 695 695 965 1,044 1,044 
Total water supplieda S(MLD) 553.65 695.00 695.00 695.00 1,044.00 1,044.00 
Total water consumed C(MLD) 553.65 681.37 661.90 643.52 1,003.85 949.09 
Fraction of water consumption reduced FRd 0.00 0.02 0.05 0.08 0.04 0.10 
Fraction of water reused FRu 0.00 0.00 0.00 0.06 0.00 0.10 
Fraction of water recycled from wastewater treatment facilities FRe 0.00 0.05 0.10 0.10 0.07 0.10 
Fraction of water reclaimed from wastewater treatment facilities FRc 0.03 0.17 0.18 0.18 0.12 0.17 
Fraction of water restored to the stock FRst 0.47 0.44 0.49 0.54 0.32 0.53 
Fraction of total volume of water lost L 0.20 0.18 0.15 0.12 0.16 0.10 

MLD, million liters per day. 1 MLD = 1000 m3/d

aTotal water supplied = Freshwater and water supplied through any of the Reuse, Recycle and Reclamation strategies.

Considering the city's population growth, the population for 2022, 2030 and 2045 is estimated using the incremental increase method using past census data (Census, 2011) (refer Table X1 in (SI-01)). Based on the population forecast, water demand was estimated using the information shared in PCMC (2016), which was evaluated to be 695 and 1044 MLD for 2030 and 2045, respectively. Detailed calculations about the same are provided in Table X2 of SI-01.

The input data about water supplied, consumed and fraction of Rs for S1 are provided in Table X3 of SI-01, whereas input data for S2 and S5 for the years 2030 and 2045 as per PCMC plans are provided in Tables X4 and X7 in SI-01, respectively. For the input data in the third scenario, JJM-U recommends reducing the NRW by 20% and increasing the Recycle and Reuse strategies by 20% (JJM-U, 2021). JJM-U also recommends rejuvenating the water bodies; thus, input data incorporating the JJM-U recommendations for S3 is given in Table X5 of SI-01.

Scenarios for the CE Phases 1 and 2 are developed considering the city's water management plan and the extent to which it can accelerate the application of 5Rs strategies in 2030 and 2045. Scenarios S4 and S6 are formulated by considering land-use of Zone A in PCMC, which was studied and approximately extrapolated to the city level for estimating the potential of 5Rs across the city. Zone A comprises four wards covering around 9% of the city's total area (PCMC, 2021). By studying the land-use map (refer Figure 4), it was estimated that until 2030, at least 5 MLD of water consumption could be reduced by introducing policies suitable for decreasing water consumption (PN, 2023).
Fig. 4

Zone A in Pimpri-Chinchwad city selected for estimating the potential of Reduce, Reuse, Recycle and Reclamation strategies to evaluate WCI and WCI-2.0 showing variation of land types (PCMC – Pimpri-Chinchwad Municipal Corporation).

Fig. 4

Zone A in Pimpri-Chinchwad city selected for estimating the potential of Reduce, Reuse, Recycle and Reclamation strategies to evaluate WCI and WCI-2.0 showing variation of land types (PCMC – Pimpri-Chinchwad Municipal Corporation).

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Further, since Reuse is not a common strategy, around 3.5 MLD of water can still be reused in the zone through awareness generation and encouragement to households, industries and commercial complexes. The PCMC emphasizes recycling water at the building level (TOI, 2019) and with the residential water demand of approximately 55 MLD (MoHUA, 2022), recycling around 6 MLD of water is feasible. Similarly, by 2045, improvement in leakages and efficient use of water can further reduce the water demand by around 10 MLD. Moreover, the reuse and recycling of used water can also be increased to around 10 MLD in Zone A. Since Reclamation and Restoration are not priority strategies, the quantity of water reclaimed and restored is assumed as per current PCMC plans for the years 2030 and 2045.

Considering the land-use of Zone A and approximately extrapolating it to the city level, the following are the assumptions made in Scenarios 4 and 6. In 2030, for water supply of 695 MLD, water consumption is assumed to be: reduced around 51 MLD (8%), reused 39 MLD (6%), recycled 64 MLD (10%), reclaimed as per PCMC plans 119 MLD (18%). Assuming 100% treatment and compliance with disposal standards, leading to restored water quantity of around 345 MLD (54%) and the remaining 77 MLD (12%) are considered to be consumption losses. The details are also provided in Table X6 of SI-01. Similarly, for 2045, the details are provided in Table X8 of SI-01. The input variables for all six scenarios are provided in Table 2, and the results are discussed in the following sections.

The WCI and WCI-2.0 are evaluated for the PCMC region for six scenarios. The results are provided in Table 3 where ‘VC’ is the volume of virgin water required to be supplied by PCMC. The total water consumed inside the system boundary (C) is the sum of ‘VC’ and the volume of the water recirculated inside the system boundary (refer to Figure 5) in the form of Reuse, Recycle and Reclamation. Total water supplied (S) is the sum of the total water consumed (C) and the volume of water consumption reduced (FRd.C). Water flowing into the system boundary includes (VC), while the water flowing out of the system boundary consists of the volume of water restored (FRst.C = Rst) and the total water discharged (W). Since the volume of water restored (Rst) contributes to the rejuvenation of natural waterbodies, it is deducted from ‘VC’ to evaluate actual virgin water consumed inside the system boundary (V). Figure 5 provides the line diagram showing flows and processes with recirculation inside the system boundary to represent the water mass balance for evaluating WCI and WCI-2.0. Figure 6 provides a Sankey diagram of water and wastewater flows in MLD and processes with recirculation inside the system boundary to represent the water mass balance for Scenario 6, i.e. CE Phase 2 for 2045.
Table 3

Input and output variables to evaluate water circularity indicator based on six scenarios generated for Pimpri-Chinchwad Municipal Corporation (PCMC) region as per PCMC plans, Jal Jeevan Mission (Urban) and CE Phase 1 and 2.

ScenarioS1S2S3S4S5S6
PCMC (2022)PCMC 2030JJM-U 2030CE-1 2030PCMC 2045CE-2 2045
Input variables Total water supplied S (MLD) 553.65 695.00 695.00 695.00 1,044.00 1,044.00 
Total water consumed C (MLD) 553.65 681.37 661.90 643.52 1,003.85 949.09 
Fraction of water consumption reduced FRd 0.00 0.02 0.05 0.08 0.04 0.10 
Fraction of water reused FRu 0.00 0.00 0.00 0.06 0.00 0.10 
Fraction of water recycled from wastewater treatment facilities FRe 0.00 0.05 0.10 0.10 0.07 0.10 
Fraction of water reclaimed from wastewater treatment facilities FRc 0.03 0.17 0.18 0.18 0.12 0.17 
Fraction of water restored to the stock FRst 0.47 0.44 0.49 0.54 0.32 0.53 
Output variables Volume of virgin water consumed VC (MLD) 535.00 528.65 477.06 421.91 814.93 598.62 
Fraction of total volume of water lost L 0.20 0.18 0.15 0.12 0.16 0.10 
Volume of water restored Rst (MLD) 262.24 300.28 322.16 344.83 318.08 503.71 
Actual virgin water V (MLD) 272.76 228.37 154.90 77.07 496.85 94.91 
Volume of untreated water generated W0 (MLD) 162.03 105.73 55.62 0.00 336.23 0.00 
Total water discharged W (MLD) 272.76 228.37 154.90 77.07 496.85 94.91 
Linear flow index LFI 0.49 0.34 0.23 0.12 0.49 0.10 
Water circularity indicator WCI 0.51 0.66 0.77 0.88 0.51 0.90 
Improved WCI WCI-2.0 0.26 0.42 0.52 0.63 0.35 0.67 
VC Inflows (MLD) 535.00 528.65 477.06 421.91 814.93 598.62 
W + Rst Outflows (MLD) 535.00 528.65 477.06 421.91 814.93 598.62 
ScenarioS1S2S3S4S5S6
PCMC (2022)PCMC 2030JJM-U 2030CE-1 2030PCMC 2045CE-2 2045
Input variables Total water supplied S (MLD) 553.65 695.00 695.00 695.00 1,044.00 1,044.00 
Total water consumed C (MLD) 553.65 681.37 661.90 643.52 1,003.85 949.09 
Fraction of water consumption reduced FRd 0.00 0.02 0.05 0.08 0.04 0.10 
Fraction of water reused FRu 0.00 0.00 0.00 0.06 0.00 0.10 
Fraction of water recycled from wastewater treatment facilities FRe 0.00 0.05 0.10 0.10 0.07 0.10 
Fraction of water reclaimed from wastewater treatment facilities FRc 0.03 0.17 0.18 0.18 0.12 0.17 
Fraction of water restored to the stock FRst 0.47 0.44 0.49 0.54 0.32 0.53 
Output variables Volume of virgin water consumed VC (MLD) 535.00 528.65 477.06 421.91 814.93 598.62 
Fraction of total volume of water lost L 0.20 0.18 0.15 0.12 0.16 0.10 
Volume of water restored Rst (MLD) 262.24 300.28 322.16 344.83 318.08 503.71 
Actual virgin water V (MLD) 272.76 228.37 154.90 77.07 496.85 94.91 
Volume of untreated water generated W0 (MLD) 162.03 105.73 55.62 0.00 336.23 0.00 
Total water discharged W (MLD) 272.76 228.37 154.90 77.07 496.85 94.91 
Linear flow index LFI 0.49 0.34 0.23 0.12 0.49 0.10 
Water circularity indicator WCI 0.51 0.66 0.77 0.88 0.51 0.90 
Improved WCI WCI-2.0 0.26 0.42 0.52 0.63 0.35 0.67 
VC Inflows (MLD) 535.00 528.65 477.06 421.91 814.93 598.62 
W + Rst Outflows (MLD) 535.00 528.65 477.06 421.91 814.93 598.62 
Fig. 5

Water and wastewater flows and processes with recirculation inside the system boundary to represent the water mass balance. The continuous line indicates a direct flow, dotted line indicates an indirect flow, and each flow is annotated at the respective location.

Fig. 5

Water and wastewater flows and processes with recirculation inside the system boundary to represent the water mass balance. The continuous line indicates a direct flow, dotted line indicates an indirect flow, and each flow is annotated at the respective location.

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Fig. 6

Sankey diagram for water and wastewater flows in million liters per day (MLD) and processes with recirculation inside the system boundary to represent the water mass balance for Scenario 6 (CE Phase 2–2045). The continuous line indicates a direct flow, dotted line indicates an indirect flow, and each flow is annotated at the respective location.

Fig. 6

Sankey diagram for water and wastewater flows in million liters per day (MLD) and processes with recirculation inside the system boundary to represent the water mass balance for Scenario 6 (CE Phase 2–2045). The continuous line indicates a direct flow, dotted line indicates an indirect flow, and each flow is annotated at the respective location.

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Scenario comparison

PCMC is supplying 535 MLD of virgin water and around 280 ML of wastewater is treated with the supply of about 19 MLD reclaimed water to the city (refer Figure X1 SI-01). In 2030, the scenario comparison indicates that PCMC can continue with the current supply of virgin water quantity of around 535 MLD for S2 (refer Table 3) with recirculation of about 150 MLD (refer Figure X2 SI-01). However, for S3 as per JJM-U, recirculation of around 180 MLD would result in around 10% reduction in virgin water to be supplied (VC = 477.06 MLD) compared to that of PCMC plans (refer Figure X3 SI-01). An additional 10% decrease in virgin water quantity would be achieved (VC = 421.91 MLD) as per S4, with a recirculation of around 220 MLD (refer Figure X4 SI-01).

In 2045, the city would require an additional 280 MLD virgin water to cater to the demand in S5, which is beyond the scope of water resources available and planned by PCMC. The recirculation of around 190 MLD (refer Figure X5 in SI-01) is also not sufficient to meet the 2045 demand. Interestingly, increasing the recirculation to around 350 MLD in S6 results in around 27% (about 216 MLD) reduction in virgin water quantity compared to PCMC plans (refer Figure X6 SI-01).

In 2030, the volume of untreated water generated (105.73 MLD) is highest in S2, which reduces to 55.62 MLD in S3, while no untreated water is generated in S4. Similarly, in 2045, the untreated water generated is 336.23 MLD in S5, while no untreated water is generated in S6. The Sankey diagrams depicting the water flows for all six scenarios are provided in Figure X1-Figure X5 in SI-01.

Increasing recirculation improves the circularity as well as the indicator, as evident from the WCI and WCI-2.0 values. The comparison between WCI and WCI-2.0 is discussed in the following sub-sections.

WCI and WCI-2.0

The indicator values are lower for scenarios as per PCMC plans than those for the scenarios recommended by JJM-U or CE Phase 1 and 2 (refer Figure 7). For all six scenarios, the WCI-2.0 is less than the WCI values. The principal difference between WCI and WCI-2.0 is the application of weightage to all the Rs and incorporating the Reduce strategy.
Fig. 7

Variation of WCI and WCI-2.0 for 2022, 2030 and 2045 as per plan by Pimpri-Chinchwad Municipal Corporation, 2030 as per JJM-U (Jal Jeevan Mission (Urban)), CE potential in 2030 and 2045 as CE Phases 1 and 2.

Fig. 7

Variation of WCI and WCI-2.0 for 2022, 2030 and 2045 as per plan by Pimpri-Chinchwad Municipal Corporation, 2030 as per JJM-U (Jal Jeevan Mission (Urban)), CE potential in 2030 and 2045 as CE Phases 1 and 2.

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In S1, the indicator value descends from 0.51 (WCI) to 0.26 (WCI-2.0) as the significant proportion of water is Restored, which is the least priority strategy acquiring the highest effort. In S2, the WCI value improves to 0.66 compared to S1, due to the introduction of Reduce and Recycle strategies and increased Reclamation. However, Restoration being the dominant strategy declines the WCI-2.0 value to 0.42. An increase in Reduce, Recycle and Reclamation in S3 further improves the value of WCI; nonetheless, Restoration declines the WCI-2.0 value. Similarly, in S4, the Reuse strategy is introduced favorably increasing the WCI values despite that WCI-2.0 values descending because of Restoration. The point of attention is that the WCI-2.0 provides valuable insights into the direction in which development is missing or desired. In 2045, extensive water demand and comparatively nominal infrastructure development plans by PCMC degrade the WCI and WCI-2.0 values for S5. However, in S6, the WCI and WCI-2.0 values rise because of expansion in all the 5Rs strategies. The WCI-2.0 value could be further improved if more water would be Reduced, Reused and Recycled than Reclaimed and Restored. It is evident that prioritizing the Rs can help in increasing the circularity of water in the desired direction where the WCI-2.0 value reaches near 1. Similar to WCI, the WCI-2.0 value ranges from 0 and near to 1, with 0 indicating a completely linear system and 1 indicating complete recirculation of water inside the system boundary. It can also be inferred that prioritizing CE strategies in the initial stage of the water cycle would be beneficial and more impactful than later stages, the implications of which are discussed in the succeeding section.

Evaluation of WCI-2.0 as per PCMC plan for 2030 and 2045 indicates that the current plans will not be effective in the future from a CE perspective. There is a further need for improvement in water and wastewater management strategies such that the WCI-2.0 value increases in the future. This need can be taken as an opportunity to prioritize 5Rs strategies and plan future water and wastewater infrastructure accordingly.

The water sector at the global level faces an imbalance in the urban water cycle because of urbanization (Vörösmarty & Sahagian, 2000) and inappropriate UWM, and there is a dire need to adopt measures that can tackle the present water crises effectively. In India also, excessive virgin water consumption (Cronin et al., 2014) and untreated wastewater disposal into natural water bodies (Asolekar et al., 2014; Williams et al., 2019) are affecting the overall water balance. The water and wastewater systems in India are broadly managed in a centralized manner, and treatment is primarily carried out in large-scale centralized facilities. Freshwater is treated and supplied through old, long transmission and distribution systems, which need large-scale improvements (Hastak et al., 2016). Leakages and water theft have become common practice, increasing water losses. To cater to the increasing water demand, public utilities are finding new raw water sources at distant locations from the city and also considering desalination as a possible option to meet increasing water demand (Thakkar, 2021). However, both the strategies mentioned above are resource-demanding and energy-intensive. On the contrary, Reducing water consumption and loss can significantly decrease the overall water demand (Gleick et al., 2003). Thus, policies such as providing subsidies on the cost of water-efficient devices and tax incentives on narrowing down domestic, industrial or agricultural consumption can reduce water consumption. One such success story is of the agrarian state of Punjab, India, where the state government, along with the World Bank, initiated an innovative ‘Paani Bachao, Paisa Kamao’ (Save Water, Earn Money) scheme for farmers to reduce groundwater consumption. As a result, around 6–25% of water was saved without affecting the crop yield (World Bank, 2023). Thus, investment in such initiatives toward the Reduce strategy can be prioritized before and during the consumption stage.

Apart from water supply systems, wastewater infrastructure management has distinct challenges. Wastewater management is predominantly experiencing a lack of attention from the authorities. As per the recent report on the inventory of STPs in India, the total wastewater generation of around 72,368 MLD, out of which 20,235 MLD is treated, thereby disposing of the remaining 52,133 MLD of wastewater into the natural environment (CPCB, 2021). This lack of sewerage infrastructure can be an opportunity to consider the Reuse, Recycle and Reclaim strategies while planning future infrastructure based on market requirements (World Bank, 2016). However, there is a lack of appropriate policies to support the use of treated wastewater (Goyal & Kumar, 2022). Ministry of Jal Shakti, Government of India has recently proposed a ‘Framework for safe use of treated water’ (MoJS, 2022), which allows the usage of treated wastewater, yet the technical standards are not specified, making its application ambiguous. Therefore, there is a need for specific guidelines and standards for using treated wastewater and a comprehensive monitoring system. Policies to support tax incentives to the users of treated wastewater to appreciate and expand the market are suggested. For example, Koradi and Khaperkheda thermal power plants in Nagpur, India, are two of the district's four major thermal power plants using extensive water for power generation (MAHAGENCO, 2017). To meet the increasing water demand, Maharashtra State Power Generation Company Limited (MAGAGENCO) has developed an agreement with Nagpur Municipal Corporation to treat and use the wastewater generated in the city for power generation, eventually reducing the freshwater demand by 290 MLD (MAHAGENCO, 2022). Although sewage reclamation required extensive infrastructure for conveyance, operation, and maintenance, it was more worthwhile than treating and disposing of the wastewater.

Moreover, infrastructure planning can also consider Restoring urban spaces based on land and resource availability. One example is of a dry water body in Rajokri, Delhi, India. The water body dried with increasing urbanization, and the lake revival was carried out using domestic wastewater treatment with no electricity consumption (Srivastava & Prathna, 2021). The rejuvenation of the water body also improved the area's groundwater level and ecosystem. Rejuvenation or restoration is beneficial under a controlled monitoring protocol, which is unfortunately not followed proactively. For example, the sewage treatment inventory of India also reveals that only 12,197 MLD of wastewater treated is as per compliance standards for disposal (CPCB, 2021). The remaining water, i.e. 60,171 MLD (about 83%), is disposed of into the natural environment, leading to pollution of freshwater sources. Thus, in the absence of a compliance and monitoring system for wastewater disposal, not prioritizing Restore strategy is paramount. Basically, there is a need for a comprehensive monitoring protocol in which WCI-2.0 can prove to be a contributory indicator.

The above-discussed water management scenarios of each city in India are contextual based on local conditions. However, planning of urban water infrastructure in India needs holistic thinking by prioritizing and ranking CE strategies in the future (Capodaglio et al., 2017; Kalbar & Lokhande, 2023). In any given system, the prioritization order of Rs would be mainly the same, i.e., Reduce > Reuse > Recycle > Reclaim > Restore. Nonetheless, Recycle and Reclaim strategies can be interchanged depending on the application scale. The weight allocation is at the stakeholders' discretion by incorporating local conditions. Improved WCI, i.e. WCI-2.0, offers guidance on prioritizing among the 5Rs to enhance the water circularity of the region under consideration. Insights gained from WCI-2.0 can aid utilities in achieving urban water balance and policy implications. Thus, by reducing freshwater consumption, appropriately managing water and wastewater infrastructure by incorporating CE strategies, and prohibiting the disposal of untreated wastewater, utilities in India can achieve urban water goals.

Measuring circularity has been a prime focus for the research community across all sectors. Such measurements are also vital for utilities and municipal bodies during infrastructure planning. In the water sector, attempts have been made to evaluate the water circularity and a novel WCI has been developed using the 5Rs (Reduce, Reuse, Recycle, Reclaim and Restore) strategies of CE. In WCI, all the 5Rs are considered equally important; however, each R has advantages or limitations when implemented in a real-life situation. Also, each R requires different kinds of effort during application. Hence,

  • The current study proposes a methodology for prioritizing the 5Rs based on the effort needed to fulfill their application for a typical city in India, i.e. region under the jurisdiction of Pimpri-Chinchwad Municipal Corporation (PCMC).

  • The 5Rs are prioritized based on the waste management hierarchy wherein Reduce is the bull's eye strategy, i.e. priority strategy, followed by Reuse, Recycle, Reclaim, and Restore.

  • Weights are then assigned to each R, indicating its influence in achieving water circularity and thus, WCI is reformulated and improved to WCI-2.0.

India is facing water scarcity, which will worsen in the coming decades. Authorities need to make decisions toward the efficient allocation of funds and resources. There will always be a situation wherein the authority needs to decide which of the 5Rs should be focused on first, wherein the WCI-2.0 can provide direction for the decision-making process. WCI-2.0 is useful when the authorities intend to accelerate the water circularity situation of the region under consideration. It offers valuable insights into the efforts that can be directed by utility managers, planners, investors, or decision-makers to achieve water circularity. For example, in case study of PCMC, the corporation is currently focusing on wastewater treatment for reclamation and restoration, because of which the difference in WCI (0.51) and WCI-2.0 (0.26) is high. Further, for the scenario in 2045, the water resources available are insufficient to cater to the freshwater demand of about 815 MLD. There is a need to shift focus from treatment and disposal to distributed and decentralized water and wastewater management for efficient UWM. Extensive infrastructure investments are planned in the coming decades, which must first be directed toward reducing water consumption and losses, followed by localized reuse as the city is highly industrialized. Localized reuse and recycling will eradicate the need to build giant water supply and sewerage infrastructure to manage freshwater and wastewater.

In conclusion, the assessment using the WCI-2.0 offers a valuable indicator for enhancing the efficiency of water systems, eventually contributing to the global efforts to address water crises and ensure the availability of clean and reliable water for future generations. Identifying the optimal value of WCI-2.0 from economic, environmental and social perspectives can be carried out considering region-specific data in future, which would help in benchmarking. Thus, benchmarking of WCI-2.0 can be used to propose policies supporting urban water balance. WCI-2.0 has the potential to change the prospects of the urban water sector for the region under consideration.

The first author is grateful to Ministry of Education, Government of India, for the scholarship under Teaching Assistantship category at Indian Institute of Technology Bombay, India. The work received partial funding from the Department of Science and Technology, Government of India through the project ‘Innovation Centre for Eco-prudent Wastewater Solutions (IC-EcoWS)’ project number DST/TM/WTI/WIC/2K17/83(G). Additionally, the authors are grateful to the Editor and two anonymous Reviewers for their valuable comments and suggestions that have substantially improved the manuscript.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.

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