A RIVER ENVIRONMENT RELATIVE COMPARISON MODEL BASED ON THE RANKING USING MULTIPLE WATER QUALITY INDICATORS

Abstract

This study aims to develop a comprehensive river environment comparison model for the 109 Class-A watersheds in Japan, which are designated as the most important watersheds and are under the jurisdiction of the Japanese Central Government. River environmental comparison is essential for river management and prioritization of environmental improvement. Over the last 50 years, the river environmental comparison in Japan has been based on a single water quality indicator, BOD, due to organic pollution being the most serious water quality issue. However, a comprehensive comparison model that considers multiple water quality indicators is needed as organic pollution has been largely controlled. This study develops a statistical comparison model by ranking the rivers with multiple environmental indicators and defines an Evaluation Score (ES) using the Multivariate Distribution Theory. The verification process has demonstrated this comparison model is reliable and valid. This model is also capable of identifying the causes of low ranking and the effective measures to improve the ranking. This study is expected to contribute to the establishment of a more reliable river environmental planning and management methodology.