12 Mar 2018

Development of a Cost-Effective River Water Quality Index: A Case Study of West Java Province, Indonesia

Arief Dhany Sutadian
Victoria University, Australia

Abstract

Having good water quality is important for a healthy river. However, it is difficult to quantify the state of river water quality due to the large choice of possible water quality parameters used to describe it. On the other hand, insufficient funding, particularly in developing countries, is one of the most common constraints towards monitoring all water quality parameters of a river as it is laborious and expensive. Given these facts, Water Quality Indices (WQIs) have been one of the most commonly used approaches across the world in evaluating river water quality effectively. A WQI is a useful tool to define the state of water quality in a body of water which can be used for decision making and operational management by the water authorities. It can also be used to compare the water quality of rivers spatially and temporarily, and to provide water quality status reports to policy makers and the public in a simple and an understandable manner.

Several WQIs have been developed by different agencies and researchers with the aim to establish their own indices or improve the existing indices. However, no single WQI has been globally accepted. In West Java and other provinces in Indonesia, the use of WQIs were introduced in the early 1990s.

The Ministry of Environment (MoE) of Indonesia adopted the Storet Index and the Water Pollution Index (WPI) for use in Indonesian rivers. However both these indices had been developed based on the information on specific regions and areas without considering the local conditions of West Java, such as appropriate parameters in the index which suit West Java conditions and parameter weights that consider West Java stakeholder opinion. Therefore, at a particular monitoring station, many parameters have been monitored, which has led to increased monitoring cost in the field and increased cost in the use of WQIs. Therefore, this study aims at developing a new WQI for use in the rivers in the West Java Province, called the West Java Water Quality Index (WJWQI), that is specifically developed to address the limitations of the currently used indices, namely the inability to make  accurate comparisons of the general status of water quality in West Java rivers, the inability to make these comparisons in a cost effective manner, and the lack of credibility and acceptability of the currently used indices by relevant authorities in West Java (since the local conditions and local expert opinion have not been considered in the development of the currently used indices).  The development of the WJWQI involved   four   steps,  which   are   selection   of   parameters,   obtaining   sub-index   values (transformation to a common scale), establishing weights, and aggregation of sub-indices to produce the final index.

The following issues associated with the development of WJWQI were addressed in this study:
1)   A new methodology for the selection of parameters based on the statistical assessment for parameter redundancy
      and the inclusion of three factors that represented criticality for cost effective water quality monitoring. This
      reduced the number of water quality parameters to be measured, which in turn reduced the cost of monitoring and
      the cost of using WJWQI.
2)   The involvement of local experts’ opinion in identifying parameter weights, and
3)   Uncertainty and sensitivity analysis to determine the robustness of WJWQI. Accordingly, these improvements
      increased the credibility and acceptability of WJWQI to be used by relevant authorities in West Java.

The results of the application of WJWQI in West Java rivers provided information on the current conditions of water quality in these rivers in a more cost-effective way, and provided a comparison of the general status of water quality in these rivers. The latter was possible, since WJWQI considered a common set of parameters (which is representative of all aspects of water quality in the rivers), and hence these common parameters are able to be monitored for all West Java rivers. This information obtained from WJWQI can be used by relevant authorities to design appropriate programs to improve their management of water quality for rivers in West Java.

The WJWQI can be used to  replace the  currently used  WQIs  in  West Java,  since it  has addressed the limitations of the currently used WQIs in West Java. This index with some modifications, can also be applied to rivers in other provinces of Indonesia and worldwide.

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