River basin change index for integrated river basin management of Langat River, Malaysia

River basins are dynamic over space and time, and any management intervention has implications for the system as a whole. Integrated river basin management (IRBM) rests on the principle that the river basin ecosystems, including the accompanying wetland and groundwater systems, function in their natural state as the source of freshwater to support the basin's water needs.

The European Union Water Framework Directive (WFD) has made river basin management plans (RBMPs) an essential component to protect, improve and sustainably manage water resources. Nonetheless, its lack of success can be attributed to, among others, missing financial and personal resources, lack of acceptance or challenges in allocating available and suitable areas (Evers, 2016). Giakoumis & Voulvoulis (2018) identified the barriers to IRBM implementation within the EU as the different interpretations of the Directive's objectives and the lack of concrete support for the policy shift. Furthermore, unresolved exemptions since its negotiation, ambiguity and compromises observed have been detrimental to IRBM transposition. EEAC Network (2019) corroborated that the lack of adequate financing, limited uptake of the WFD's economic thinking and the lack of a paradigm shift to a systemic approach in water policies are the reasons for the partial success.

According to members of the American Water Works Association (AWWA), the current entrenched interests among water utilities, municipalities, and water rights holders are very powerful in safeguarding their own interests. Efforts are required to examine how governance at all levels may change, as well as the need to connect governance and other water drivers (LaFrance, 2022). Rojas et al. (2020) opined that the way forward is consolidation, regionalisation and watershed partnerships, with recognition of collaborative governance model.

Elfithri et al. (2011) highlighted the need for improved professional capability and increased financial, legislative, managerial and political capacity to address both the water-related and the river-related issues for IRBM in Malaysia. Until recent years, the lack of uniform water law, institutional capacity and financial support are still recognised as among the key limiting factors to effective IRBM implementation in Malaysia. It is thus of great importance that the enabling environment, institutional setup and management instrument be continuously improved and realigned to work in tandem to achieve the desired outcome (ASM, 2015).

River basin organisation (RBO) may be defined as a societal entity created to manage, develop or monitor natural water resources in a large watershed (USACE, 2006). The RBO is instrumental in the implementation and execution of related IRBM strategies and action plans. Participatory and self-management institutional framework for administering the catchments through a dedicated RBO-type body with a combination of engineering, social and scientific management is crucial to the success of IRBM (Santhosh Kumar & Prakash, 2018). Nevertheless, it is not surprising that RBO may lack or be deprived of the autonomous power required for its role under the institutional structure (e.g. Delipınara & Karpuzcub, 2017). It is not uncommon for some influential sectors or groups to exhibit occasional dominance due to their resource contribution to the process, contemporary influence or statutory authority (Sigalla et al., 2021). Other deficiencies include governance-related challenges such as the fragmentation of institutions, the interconnection with other essential services and overlapping competencies (Stein et al., 2023).

According to the World Bank model (2006), the roles and functions of the RBO may evolve as the circumstances dictate. As it matures, an RBO should have moved past project execution, operation and maintenance and raising funds, and more into monitoring, policy and strategy development, community engagement and sustainable resource management. In its essence and spirit, IRBM implementation should not be considered on an ad-hoc basis or in a standalone programme but should be an iterative process to facilitate social learning to bring about permanent positive change (Mokhtar et al., 2010).

Ge et al. (2018) introduced an IRBM decision support framework, where the UN's Sustainable Development Goals (SDGs) were converted into tangible and actionable goals, targets and indicators to facilitate the implementation and promote progress at the river basin level. This is integrated with a multi-scenario analysis, considering different scenarios of future changes to derive development pathways. Shafiei et al. (2022) introduce a framework for sustainability assessment at the river basin level, which comprises 25 indicators in four main categories, namely, technical, environmental, economic and social, aggregated using a proposed weighting scheme. Grigg (2023) uses a social science policy tool known as the Institutional Analysis and Development framework (IAD) from the seminal work by Ostrom (2007), which garnered the year 2009 Nobel Prize in economics. The approach is suited for the study of complex problems with a mixture of methodologies, to perform root-cause analysis for decision support of an urban water problem. Stein et al. (2023) introduce the Diagnostic Water Governance Tool (DWGT) which links context-specific assessment to evidence-based instrument recommendations to tackle identified deficits. The above approaches are most useful for causal analysis (assessment) and logical deduction to arrive at the most pertinent recommendations (solution) to prevalent basin issues. However, they are heavily reliant on self-appraisal or expert opinion in lieu of exploiting basin data which can better conjure a comprehensive understanding of the IRBM status.

Successful implementation of IRBM is expected to produce measurable or discernible positive outcomes. By introducing a set of objective assessment criteria and/or methodology to measure the attainment or performance of IRBM implementation over time, whether within a river basin or for cross-comparison between river basins, it can serve as a very important continuous improvement process. Furthermore, it is preferable for the measurement criteria to encompass multiple dimensions in order to capture the diverse spectrum of IRBM. This ensures that the complexity and interconnectedness of the different components are adequately assessed to give a comprehensive understanding of the status of IRBM, including insights into some of the less tangible or obscure outcomes which are not amenable to measurement. Shortfalls can then be identified so that appropriate remedial actions can be introduced for timely interventions.

However, the majority of data-driven assessment frameworks adopt a scorecard system approach, which involves tracking a set of key indicators linked to the respective roles and responsibilities of the RBO and IRBM agencies in IRBM. The measured performance thus often carries the connotation of success or failure, which can be off-putting especially since many IRBM initiatives often hinge upon multiple intertwined factors which may be within or without the organisational control. To promote collaborative IRBM actions, the assessment exercise should not be seen as punitive in nature which would otherwise invite resistance and resentment from the basin stakeholders. The framework should instead emphasise the outcome of a collective effort where progress is celebrated together, whereas setbacks, hiccups or challenges are jointly acknowledged for the purpose of the improvement process. This will help to win over the commitment, cooperation and collaboration of all stakeholders in the IRBM partnership, as opposed to finger-pointing or blame.

Moreover, it is important to recognise that the many different strategies and action plans are diverse in nature, ranging from physical projects, engineering studies, planning and execution, governance and management, monitoring and enforcement, incentives and alternatives, and preservation effort. Each of these may produce results in different forms, time horizons and under different denominators. Besides, the year-to-year changes of the various dependent or independent variables in the basin, naturally driven or human-induced, may be short-term fluctuations which may not reflect the long-term trend.

In this paper, a multi-faceted IRBM assessment framework, which encompasses water governance, RBO capacity and resources and the technical outcomes, is proposed. A comprehensive set of indicators and sub-indicators are developed and assessed using different methodologies including stakeholder opinion and published data from related agencies. A uniform scoring approach with a suitable denominator is introduced to aggregate the diverse data source into a proposed river basin change index (RBCI) to evaluate the status of IRBM implementation in the basin. A pilot test of the novel approach is carried out for the Langat River IRBM plan (2015–2020).

Langat River basin (LRB) is the largest river basin in the state of Selangor, Malaysia, with an area of 2,432 km² and a latitude of 2°40′–3°20′N and a longitude of 101°10′–102°00′E. It comprises three (3) distinct zones: the mountainous zone at the northeast on the upstream, the hilly area in the middle basin area and the flat alluvial plane on the downstream near the river mouth.

In the past two decades, LRB has experienced the spillover effect of accelerated development from the adjacent Klang River basin, the most urbanised region of the country. Drastic changes in land use occurred due to the conversion of forest and agricultural lands to residential, commercial and industrial developments. The built-up area in the basin has increased over the period from about 23,018 km² (7.85%) in the year 1996 to 119,587 km² (40.70%) in the year 2016, whereas the agricultural land area reduced significantly from 60.22 to 25.7% (Majid et al., 2018). In 2016, there remained 17.7% of forest land, and 11.2% of wetlands and swamps, with a small fraction of quarry and mining land use. Figure 1 shows the land use map of the basin in the year 2018 with highly concentrated development in the middle basin area.

Surface water constitutes the primary water resource in LRB. The basin's raw water is supplied to three Selangor districts. Furthermore, ex-basin reticulation draws heavily from the Langat system to areas outside of the Langat natural basin boundary. As a net exporter of potable water, LRB needs to prioritise its self-sufficiency in terms of water supply and demand for long-term sustainability.

Besides water supply, Langat River is used for recreation, fishery, irrigation and sand mining. Industrial activities, irrigation runoff, animal husbandry, aquaculture, discharge from sewerage treatment plants (STPs), solid waste and illegal dumping, sullage, river sand mining and land clearing activities in the basin are among the major sources of pollution. Water abstraction for both potable and non-potable use in the basin has always been given higher priority over fulfilling the in-stream environmental flow requirement.

Flash flood is the major flood type in the basin especially in the urban centres characterised by a high percentage of impervious surface. Furthermore, the lower basin area is susceptible to coastal flooding, especially during high tide events due to the low-lying terrain. The lack of flood storage and poor river and stormwater maintenance are the primary reasons for frequent flood occurrences. Under the IRBM plan, 5% of the reservoir storage of Langat Dam in the basin was allocated for flood mitigation during the monsoon although it is not designed for the said purpose.

Inland navigation activities along the Langat River have gained traction in recent years driven by industrial activities. With the increased number of jetties and vessels traversing the river, there is a need for strong governance, planning and management of the river waterway to ensure sustainable and safe navigational activities.

In Malaysia, water is under the jurisdiction of the state as mandated under the Federal Constitution of Malaysia. In the year 1998, the National Water Resources Council (NWRC) was formed and made provision for the Federal Government to oversee aspects of water not under the jurisdiction of the states. The Water Services and Industry Act (WSIA) 2006 subsequently placed water utilities under the concurrent list shared between the federal and the state governments. However, the NWRC has not been provided with the legal mandate for carrying out the function of coordinating everything related to water (ASM, 2016). Furthermore, there is no dedicated department with regard to water at the ministerial level.

IRBM planning is defined as a process of coordinating the conservation, management and development of water, land and related resources across sectors within a river basin in order to maximise the economic and social benefits derived from water resources in an equitable manner while preserving, and where necessary, restoring freshwater ecosystems (DID, 2009). It is a subset of integrated water resource management (IWRM) and is the approach or tool to achieve IWRM objectives.

The National Water Resources Study (NWRS) 2010–2050 (DID, 2010) recommended that all states set up their respective water resources management institution in alignment with the federal structure. It defines RBO as a fully functional river basin management organisation with institutional and legal structure to address almost all aspects of water resources management using the IWRM and IRBM concepts and approaches.

The Selangor Water Management Council (LUAS) is the official state RBO under the legislative powers of the Selangor Waters Management Enactment 1999 and its subsequent subsidiary regulations. The main objective of LUAS is to ensure sustainable water resource management to support state development through planning, operation, coordination and enforcement, and by engaging the public and private sectors to increase awareness of the importance of water resources. LUAS is responsible for LRB and all other river basins in the state. However, basin water management issues are shared by other related agencies with different roles, responsibilities and jurisdictions as summarised in Table 1.

The first Langat River IRBM plan was completed in 2005 (ASM, 2014). More recently, the Langat River IRBM 2015–2020 plan was concluded. The revised IRBM plan 2022–2030 is inked as a key document to drive IRBM forward retaining the four (4) key policies, namely:

• i.

  Policy 1: Ensure sufficient water to meet all water demands for the people, food, development and the environment.

• ii.

  Policy 2: Ensure clean water for the beneficial uses of all stakeholders.

• iii.

  Policy 3: Reduce the risk of flooding to protect residents and properties.

• iv.

  Policy 4: Facilities for inland river navigation to ensure sustainable and safe inland navigation activities.

Each policy consists of several strategies, and each strategy is supported by relevant control measures to be championed by relevant agencies or authorities. In total, there are 17 strategies and 68 control measures. Furthermore, each control measure comprises one or more action plans. There are in total 161 action plans.

Water governance (WG) is vital to provide the necessary policy, legislation and regulatory framework required for the successful implementation of IRBM. The Organization for Economic Co-operation and Development (OECD) defines WG as the range of political, institutional and administrative rules, practices and processes (formal and informal) through which decisions are taken and implemented, stakeholders can articulate their interests and have their concerns considered, and decision-makers are held accountable (OECD, 2015a).

The proposed WG Indicator is adapted from OECD (2018), and comprising three main categories, i.e. effectiveness, efficiency, trust and engagement. Each of the categories comprises 4 principles, and each principle comprises 3 sub-indicators, hence a total of 36 sub-indicators (Table 2). The framework encompasses the enabling environment, such as defined roles and responsibilities between agencies, capacity building, resource allocation, information sharing, innovation, transparency, stakeholder engagement, trade-offs management, monitoring and evaluation. The WG sub-indicators incorporate the necessary interface to address and resolve transboundary issues pertaining to water resources which is pertinent to LRB.

RBO is responsible to champion and drive the IRBM initiatives in a river basin. The RBO indicator is designed to measure the RBO's organisational resourcefulness and capacity in the execution of the IRBM Plan to sustain its operation and growth to fulfil its purpose and function effectively and efficiently.

The proposed RBO indicator comprises ten categories, each with three sub-indicators (Table 3), which include resource allocation and utilisation (Categories 1 and 9), licensing (Categories 2 and 10), revenue sources and generation (Categories 3–5), planning and implementation (Categories 6 and 7), and monitoring and enforcement (Category 8). Categories 6 and 7 are related to Policy 1, whereas Categories 8–10 are related to each of the Policies 2–4, respectively.

Policy 1 aims to ensure sufficient water for the current and future basin sectorial water demand. Table 4 shows the proposed Policy 1 technical indicator divided into six main categories, comprising water resources index (WRI), system capacity, reticulation network, service factor, dependency on treated water and non-revenue water (NRW).

The WRI (Category 1) is a water resource monitoring and management tool recently introduced in Malaysia. It is defined as the ratio of the actual water resource availability (WRA) to the average water resources capacity (WRC) for a consecutive duration of T day(s). For the selected point of interest (POIs), the WRA and WRC are calculated as the sum of the water storage (where applicable), inflow, outflow and withdrawal. The WRC is calculated from historical averages, whereas the WRA for the respective year. For regular conditions, the ratio of WRA/WRC is in the order of 1. The WRI essentially represents the water availability compared to historical averages, much similar to the concept of the Standard Precipitation Index (SPI) for rainfall. If WRI drops significantly below 1, it suggests that the water resources availability is lower than usual – a useful indicator of basin drought. The POIs in the present study are the two dams and the main run-of-river (ROR) water treatment plant (WTP) in the middle basin. Detailed derivation and interpretation of WRI can be referenced from Lim et al. (2023).

System capacity (Category 2) and reticulation network (Category 3) reflect the adequacy and condition of the existing water supply infrastructure. The fraction of population served (Category 4) measures the water supply coverage, whereas dependence on treated water (Category 5) measures the basin's reliance on reticulation based on per capita consumption (PCC) and NRW as well as the utilisation of groundwater. It is commonly understood that there is a practical lower limit for NRW reduction, hence suitable NRW denominators are introduced under Category 6.

The OECD (2015b) 14-point checklist for water resources allocation is not adopted herein due to the differing scope from this IRBM policy. Furthermore, the proposed list of measurable, fact-based sub-indicators is preferred over the OECD checklist which is designed to gather qualitative feedback from experts in the field.

Policy 2 is concerned with the quality of water resources in the basin.

The Malaysian Interim National Water Quality Standards (INWQS) 1985 defines beneficial water use based on the water quality index (WQI), calculated from sub-indices based on dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (AN), suspended solid (SS) and pH. Class I is suitable for environmental conservation, very sensitive aquatic species and water supply without further treatment. Class IIA is suitable for sensitive species, but would require conventional treatment for water supply, whereas Class IIB is for recreational use. It is an ultimate target to achieve at least Class II for all rivers within LRB, except if the river water characteristics are influenced by the natural environment such as peat area or near estuary. The aim is to ensure that river water quality (WQ) is readily available for human and environmental uses to sustain the riverine ecosystem. As WQ deteriorates to Class III, it is only suitable for livestock and very tolerant species, and would require extensive treatment for water supply purposes. Class IV may only be used for irrigation and Class V none of the above.

The proposed Policy 2 technical indicator comprises three main categories (Table 5). System design and operation (Category 1) combines parameters related to STP and network design as well as WTP downtime and output disruption, the latter of which is frequently associated with pollution at water sources (Ahmed et al., 2022). Categories 2 and 3 are given by the ratio of actual load to water usage and actual load to allowable load, respectively, derived from five main WQ parameters from monitoring stations in the basin.

Policy 3 addresses the problem of excess water caused by monsoonal floods, coastal floods or flash floods.

The proposed Policy 3 technical indicator comprises three main categories (Table 6), which measure the impacts of flood in terms of flood extent (Category 1), food damage (Category 2) and flood victims (Category 3). Flood extent is determined based on both spatial inundation and a number of flood events as registered by the districts. Flood damage is quantified based on the official estimate of flood economy losses. Meanwhile, flood victims are accounted for based on the number of people and households affected.

Policy 4 aims to facilitate inland river navigation through governance, planning, infrastructure and monitoring to ensure technical compliance and safety for operators and users to yield maximum benefits to the communities and minimum detrimental impacts on the environment. The policy involves the provision of infrastructure to promote the use of river transport by fishing boats, aquaculture, cargo and recreation vessels.

The proposed Policy 4 technical indicator comprises four categories: infrastructure, waterway, vessel and safety aspects (Table 7). The infrastructures are assessed in terms of the number of fishing jetties and private jetties, whereas waterway navigability is assessed in terms of dredged channel length and sedimentation rate. The total number and tonnage of registered vessels are taken as the direct measures of inland navigation adoption and popularity, whereas a number of recorded navigational accidents and complaints reflect the safety issues.

The present framework requires a set of indices for each of the WG, RBO and technical indicators, which follows a consistent scoring approach so that they can be aggregated to give the proposed RBCI. The WG sub-indicators constitute a qualitative statement. Meanwhile, the sub-indicators for the RBO indicators and technical indicators are based on related basin data, selected on the basis of relevance, under the purview of the basin operators/agencies, measurable and data availability.

For both the RBO and the technical scores, the score for each sub-indicator is derived as a ratio comparing the current value (CV) to a reference value (RV). The scores obtained are interpreted as follows, where:

• Score > 1 indicates progress towards a better condition.

• Score = 1 indicates status quo, i.e. no change in condition.

• Score < 1 indicates a regress towards a poorer condition.

Where data are unavailable, a default score of 1 is assigned. It is the intention that the relevant data shall be collected and made available in the subsequent assessment cycle. Note that the ratio may be calculated as either CV/RV, or RV/CV, depending on whether the CV may preferably be higher, or lower, compared to the RV. The RV may take the form of either:

• a temporal value (e.g. historical data based on a certain year, or period),

• a spatial value (e.g. state average or national average value) or

• a target value (based on a targeted value set by the relevant authorities).

Examples where higher CV is better are such as revenue per employee, allocation for maintenance and number of licensing. Examples where lower CV is better include PCC and NRW. Note that the use of target value as the RV may be disadvantageous if the CV is notably under-performing, in which despite improvement made, the score will only reflect diminishing regress instead of progress. In the present study, only the temporal and spatial comparisons are adopted (see notes in Tables 4–7).

The score for WG attainment is assessed through a targeted questionnaire survey conducted among representatives of these agencies. Participants are requested to rate the current status (CS) of the IRBM for each sub-indicator using a Likert-scale rating system ranging from 1 (Not in place), 2 (Under development), 3 (In place, not implemented), 4 (In place, partially implemented) to 5 (In place, fully functional). For the anticipated future change (FC) at the end of the IRBM cycle, respondents may choose +1 for improvement, −1 for decline, or 0 to indicate no change. The future status may thus be given by (CS + FC). The mean score for each of the sub-indicators is then given as (CS + FC)/CV and follows the same interpretation aforementioned.

Once all the sub-indicator scores are obtained, the score for each category (including each principle in WG) is averaged to give the overall score for WG, RBO and the respective policies. For WG, the consensus of the survey response is further analysed based on the standard deviation (SD) of the data.

The range of RBCI value obtained can be interpreted similarly to the scores as progress (>1), regress (<1) or status quo (=1). However, since the RBCI combined the multiple dimensions of IRBM, a more comprehensive interpretation of the final RBCI is suggested as shown in Table 9. Under the present proposed framework, it is agreed that changes within 10% in the score (0.9 < RBCI < 1.1) are accepted as regular year-to-year fluctuation, which reflects natural basin change. Lower values of RBCI denote under-performance of IRBM practices, negligence or disastrous basin regress. Meanwhile, higher values of RBCI can be attributed to notable improvements, outstanding or breakthroughs in IRBM practices.

The WG questionnaire survey was participated in by 40 respondents of different designations from 20 different agencies involved in Langat River IRBM (Table 1). The questionnaire was distributed, briefed and clarified in a face-to-face workshop, and the responses were collected at the end of the session.

Of the 12 principles, only ‘Finance’ is opined to be fully implemented. Eight (8) other principles are considered in place and partially implemented. ‘Policy coherence’ is in place but not implemented, which suggests underlying problems in cross-sectorial, inter-ministerial and transboundary coordination. Meanwhile, ‘Trade-offs management’ between water users is still under development. ‘Monitoring and evaluation’ is not in place, showing that systemic data collection and evaluation of IRBM implementation is lacking.

Comparing the main WG categories (Figure 4), the IRBM ‘Efficiency’ is ranked the highest, followed by IRBM ‘Effectiveness’, whereas ‘Trust and engagement’ is the poorest. This shows that more effort is required to promote national integrity and build public confidence, ensure fairness and inclusiveness of stakeholders, institutionalise the formal interface for trade-offs management and improve IRBM monitoring and evaluation.

The respondents demonstrate strong consensus on ‘Policy coherence’ and the eight principles opined to be in place and partially implemented. The other principles have medium consensus. Overall, the IRBM representatives from different agencies are in good accord with one another. The IRBM ‘Effectiveness’ category has the strongest consensus, followed by the ‘Efficiency’ category. The ‘Trust and engagement’ category is split between strong and medium consensus.

From Figure 5, it is anticipated that the new IRBM cycle will see more defined ‘Roles and responsibilities’, including closing the gap on ambiguous or overlapping jurisdiction. ‘Data and information’ availability, accessibility and useability are also expected to be significantly improved. The development of ‘Trade-offs management’ framework should be addressed to facilitate better equity across all water users. Other principles are opined to show marginal improvement, of which the least is ‘Integrity and transparency’.

The overall WG score is 1.14.

‘Revenue generation’ shows extraordinary improvement approaching 2.0. This is followed by ‘Main revenue sources’, which sees a significant increase in collection from surface water usage. There has also been a significant increase in ‘Flood allocation’ for mitigation work.

‘Water quality enforcement’ shows slight progress within 10% changes through pollutant discharge licensing, monitoring and compound issuance. ‘Alternative water usage’ remains status quo, with no new projects related to alternative water resources, rainwater harvesting, water recycling or reuse, likely due to the lack of incentive or funding for these initiatives.

Under ‘Budget and expenditure’, the development budget and expenditure are found to be notably lower than management. Meanwhile, ‘Supplementary revenues’ have shrunk. In ‘Promoting inland navigation’, the overall number of new licensing reduced except for the new jetty. For ‘Groundwater usage’, new exploration and total licensing have been reduced despite a marginal increase in new licensing, suggesting the closing down of wells. Overall, the RBO new licensing, licensing renewals and total licensing have all been reduced.

The overall RBO score is 1.06.

‘System capacity’ has shown significant improvement due to the recent completion of a new off-river storage (ORS) and WTPs, hence higher design capacity, production and reserve margin. ‘Non-revenue water’ has shown notable improvement. ‘Service factor’, which is just above the national average, is the only item using spatial RV. The score for ‘reticulation network’ is slightly above 1, with a reduced proportion of asbestos cement pipe and old meters.

‘Water resources index’ and ‘Dependence on treated water’ have shown noticeable under-performance. Reduction in WRI at all three key locations investigated indicates reduced water availability. The basin continues to show high dependence on treated water attributed to high NRW and high PCC. The exploration and development of alternative water sources such as groundwater, pond water, water recycling and reuse remain low.

River WQ at the forested and undeveloped upper basin area was reported to be at least Class II. However, it deteriorates to Class III as the river flows downstream. ‘Actual load to water usage’ has shown outstanding improvement. ‘Ratio of actual to allowable load’ also has notable improvement. The notable improvement in COD and oil and grease (O&G) in the rivers may be closely related to reduced industrial and commercial activities during the movement control order (MCO) in the year 2020 (see Section 4.3.5).

In Category 1, sewerage system design has shown improvement, including the ratio of design PE to current PE, the ratio of PE served by STP in lieu of septic tank or traditional system, and a number of accounts connected to public STP. These are important to ensure that wastewater in the basin is given appropriate treatment before its release into natural water bodies. During operation, WTP shutdown is frequently associated with pollution as a water source (e.g. Ahmed et al., 2022). Data show that the WTP downtime and water production disruption in the basin have been reduced. Here, the duration and volume are considered in lieu of the actual number of events in order to give a better indication of the condition of WQ and its impact.

Flood records show that the total number of recorded flood events in the 3 Selangor districts in the Sg Langat basin combined has more than doubled from a total of 89 for the 5-year period from 2001 to 2005 to 227 from 2016 to 2020 (DID, 2010). The increased occurrence and frequency of floods in previously flood-free areas calls for the attention of the relevant authorities, engineers and planners to jointly provide practical and workable solutions to mitigate the disaster.

Based on the basin flood data, there is a significant reduction in the number of flood victims, estimated flood damage and average annual damage. However, the number of flood events and spatial extent is higher compared to other river basins in the state.

The categorial scores (Figure 12) show that ‘Waterway’ has the highest positive change, followed by ‘Vessel’. ‘Safety’ falls into the regular fluctuation band whereas ‘Infrastructure’ is under-performing.

Figure 12 summarises the categorial scores for all four IRBM policies. The overall scores for the policies are all above 1, and well above 1.5 for Policies 2–4.

Note that Policy 1 on water sufficiency is considered at the basin scale without spatial resolutions. Furthermore, it is beyond the scope of the present study to examine water resources allocation strategy related to water entitlement or under exceptional circumstances (see, e.g., OECD, 2015b).

The over-exploitation of provisioning and the degradation of regulating services may cause a decline in the capacity of ecosystem services. Failure to account for ecological interdependencies often leads to unsustainable use of resources (Pahl-Wostl et al., 2023). However, the present assessment framework is designed based on the existing IRBM policies in which environmental conservation is not included explicitly but is incorporated indirectly under the other policies. There is no sub-indicator which specifically addresses environmental conservation or ecosystem needs due to the lack of measurable data for the intended purpose.

Both Policies 1 and 3 are susceptible to climate change factor (CCF) which can be an important denominator for the measured changes. However, the relevance of incorporating CCF into short-term comparisons from year-to-year or even up to a 5-year period may still be debatable. Hence, this is omitted from the present consideration.

In the present framework, the total number of indicators and sub-indicators varies across WG, RBO and the four policies. As a result, when the scores are aggregated to the RBCI, the actual weight applied (Table 10, column [6]) for each indicator differs from the original assigned weight (column [1]). Admittedly, the proposed weight determined by expert opinion is based on the best available information at the time. As the basin undergoes changes, the RBO can revise the weight accordingly, in consultation with basin stakeholders, to reflect the prevalent IRBM emphasis and focus. The effort to assign individual weight to every sub-indicator would be a highly subjective and strenuous task. Likewise, it is impractical to standardise the number of sub-indicators across all the domains.

Nevertheless, whenever the list of sub-indicators or the weight is altered, back calculation of past RBCI values can be undertaken to maintain consistency for long-term comparison. Where past data is not available, the unit assumption (score = 1) may be adopted although it may not be true and will affect the RBCI value nonetheless. An alternative approach is to accept empty data entry, i.e. to exclude certain sub-indicators from score averaging. For cross-basin comparison, a consistent set of weights must first be agreed upon by the participating RBOs.

In Table 11, the assigned weight used in the RBCI calculation is adjusted so that the actual weight applied equals the originally proposed values. The calculated RBCI using the original weightage gives RBCI = 1.64 (in lieu of 1.43). The results suggest that LRB has shown improvement in all domains, especially the technical indicators. The RBCI value is categorised as exceptional positive change reflecting an outstanding achievement in overall well-balanced IRBM. The findings suggest that the preceding Langat River IRBM 2015–2020 has yielded positive IRBM results. Further improvement of identified shortcomings and weaknesses shall be addressed in the IRBM plan (2022–2030).

An assessment framework which aims to provide a holistic approach to periodic appraisal of the IRBM attainment is introduced. The proposed RBCI comprises WG (36 sub-indicators), RBO (30 sub-indicators) and four technical indicators (47 sub-indicators). For WG, a questionnaire survey involving all basin stakeholders was conducted. Other data required is extracted either from official reports or from records of the relevant agencies. Analysis is performed using either temporal or spatial comparison, where a ratio in the range of 0.9–1.1 is regarded as regular year-to-year fluctuation. The RBCI is then calculated by assigning a set of proposed weights to each of the indicators.

Application of the novel approach to the LRB illustrates the relevance of the sub-indicators, the indicators and the RBCI derived. The result is sensitive to the number of sub-indicators in each domain and the proposed weight. Data availability is crucial to provide a realistic evaluation of the basin IRBM performance, especially for consistent long-term comparison. The methodology can be readily adapted to other river basins using distinct weights for the respective evaluation components following the prerogative of the basin RBO.

This paper is written based on the Langat River IRBM Study (2022–2030) funded by Selangor Water Management Authority (LUAS) Malaysia. The authors acknowledge the contributions from the stakeholders, the working team in LUAS head office and the project members from Angkasa Consulting Services Sdn. Bhd. and Chemsain Konsultant Sdn. Bhd.

Data cannot be made publicly available; readers should contact the corresponding author for details.

The authors declare there is no conflict.