First development of the Malaysian River Integrity Index (MyRII) based on biological, chemical and physical multi-metrics

Highlights

• Multi-metric river assessment system was formulated and tested.

• Reference site was established to statistically derive rating thresholds.

• Assessment system was able to delineate impairment of various degrees.

• Water chemistry metrics are not robust for measuring river integrity.

• Poor ichthyology competency impedes assessment system deployment.

Abstract

Anthropogenic pressures are causing substantial degradation to the freshwater ecosystems globally and Malaysia has not escaped such a bleak scenario. Prompted by the predicament, this study's objective was to pioneer a river assessment system that can be readily adopted to monitor, manage and drive improvement in a wholesome manner. Three sets of a priori metrics were selected to form the Ichthyofaunal Quality Index (IQI: biological), Water Quality Index (WQI: chemical) and River Physical Quality Index (RPQI: physical). These indices were further integrated on equal weighting to construct a novel Malaysian River Integrity Index (MyRII). To test its robustness, the MyRII protocol was field tested in four eco-hydrological zones located in the Kampar River water basin for 18 months to reveal its strengths, weaknesses, and establish the “excellent”, “good”, “average”, “poor” and “impaired” thresholds based on the “best performer” reference site in an empirical manner. The resultant MyRII showed a clear trend that corresponded with different levels of river impairment. Test site zone A which was a reference site with minimal disturbance achieved the highest MyRII (88.95 ± 4.29), followed by partially disturbed zone B (61.95 ± 5.90) and heavily disturbed zone C (50.00 ± 4.29). However, the MyRII in zone D (59.9 ± 6.39), which was a heavily disturbed wetland that was disjointed from the river, did not conform to such trend. Also unveiled and recognized, however, are some unexpected nuances, limitations and challenges that emerged from this study. These are critically discussed as precautions when interpreting and implementing the MyRII protocol. This study adds to the mounting body of evidence that water resource stakeholders and policymakers must look at the big picture and adopt the “balanced ecosystem” mind-set when assessing, restoring and managing the rivers as a freshwater resource.

Introduction

As the world is facing uncertainty from climate change and pollution increase, the watersheds and rivers are inevitably strained. This is compounded by population growth which demands more freshwater from the rivers to support household, industrial and recreational uses. Globally, there is already a rapidly growing literature on freshwater insecurity which paints a gloomy picture of the capacity of existing rivers to support the projected social and economic growth (Simonovic, 2002, Kuchment, 2004, Food and Agriculture Organization of the United Nations, 2008, Gerbens-Leenes et al., 2012, United Nations, 2013). Regionally, the countries in Southeast Asia, notably Malaysia have not escaped such a bleak scenario. Since the national population has risen from 2,962,795 in 1970 to 13, 725, 609 in 2000 (363% increase) of the total population (Masron et al., 2012), evidently the country needs more freshwater in the future.

Due to the inevitable geohydrological disturbances caused by the corresponding land use activities to support social and economic growth, the occurrence of river pollution, water shortage, riparian impairment and aquatic biodiversity loss are becoming common in Malaysia (Chan, 2004, Chong et al., 2010, Ministry of Natural Resources and Environment, 2011, Zainudin et al., 2013, Institution of Engineers, 2014, Academy of Sciences Malaysia, 2015, Chellaiah and Yule, 2018). Wedged between 1) increasing point and non-point water pollution, and 2) rapid population growth and development that drive rising water demand, the government has responded by launching the National Water Resource Policy in 2012. One of its key objectives was to " … provide means and measures to complement existing policy directions related to water resources so as to ensure their sustainable and equitable use, as well as to protect the integrity of the environment, ecosystems and natural heritage” (Ministry of Natural Resources and Environment, 2012). Certainly, without the proper “means and measures” to monitor and inform management processes, Malaysia stands to lose the ecosystem services offered by the rivers at an unprecedented pace.

Conventionally, only water physico-chemistry metrics are monitored in Malaysian rivers. Other “means and measures” were subjects that science knows very little about in the country. Many researchers defined and agreed that river resilience comprise three overlapping dynamic components of physical, chemical and biological integrity (Karr and Dudley, 1981, Angermeier and Karr, 1994, Rapport, 1995, Schofield and Davies, 1996, Barbour et al., 1999, Campbell, 2000, Wiens, 2002, Coles et al., 2004, Wang et al., 2014). Although the Malaysian government acknowledged the deficiency in the existing approach, a wholesome assessment system has yet to emerge. Here lies the critical gap that urgently needs to be addressed.

The importance of river biological, chemical and physical (BCP) three dimensional basic properties was first credited when the United States Environmental Protection Agency (USEPA) introduced the 1972 Clean Water Act. With regards to “integrity”, the Act envisions to “convey a concept that refers to a condition in which the natural structures and functions of ecosystem is maintained”. Under the Act, states are expected to assess, monitor and formulate objectives to restore and maintain biological, chemical and physical integrity of watershed at the ecosystem level. This also goes to point out that assessing chemical metrics alone is deemed insufficient because it does not consider the dynamism of biological communities and landscape physical variances that also affect river integrity. In diverse demographic, geohydrological and climatic dissimilarity in the US, the Act allows individual states to develop customised assessment systems and restoration projects as long as the concept of BCP is adhered to. Such approach also generally compels each state to produce assessment results that can be compared across the country for benchmarking.

Currently, there are 1055 monitoring stations located in 570 rivers in Malaysia (Amneera et al., 2013). Unfortunately, the country is still far from applying the appropriate BCP multi-disciplinary assessment for monitoring river integrity. The rivers' integrity is exclusively arbitrated by the Water Quality Index (WQI) which is largely focused on water physico-chemistry metrics. To the authors’ best knowledge, a protocol that explicitly applies the BCP multi-disciplinary approach for river assessment has yet to emerge in Malaysia or any country in the Southeast Asia so far and there is an urgent need to close the gap. The immediate issue at stake is, until a multi-disciplinary approach emerges, the integrity of rivers cannot be ascertained and the necessary database would not be available for monitoring rivers or driving improvement programs.

Therefore, this research was motivated by the Malaysian government's call to address the gap highlighted earlier (i.e. “means and measures”) and the objective of this study was to develop a protocol that is ready for use, robust and wholesome enough to include the key BCP multi-metrics. It did so by drawing lessons from best practices adopted by developed countries in constructing the protocol and testing it on a local exemplar site. Certainly, there were a great number of assessment protocols from all over the world that range from relatively simple algorithms or indices to complex multi-variate methods (Prichard et al., 1998, Norris and Hawkins, 2000, Parsons et al., 2002, State of Ohio Environmental Protection Agency, 2006, Hughes et al., 2010, Oliveira et al., 2011, Tanago and Jalon, 2011, Wang et al., 2014, Mostafavi et al., 2015, Li et al., 2017, Rinaldi et al., 2017, Yu et al., 2019). A “silver bullet”, or ideal protocol, was elusive and some trade-offs were to be expected.

Since river management process involves a wide range of stakeholders, this study was also aimed at formulating a systematic protocol that is 1) easily understood, 2) practical, 3) sensitive against biases, and 4) scientifically sound for decision makers who may be non-experts. A set of high resolution multi-disciplinary metrics that were practical and manageable was identified and applied to measure the direct responses to natural or anthropogenic disturbances. The results were then synthesized and summarized into a single index for characterizing river “naturalness” or impairment. The multi-disciplinary index was to be called the Malaysian River Integrity Index, or MyRII.