Evaluation of Water Management Effectiveness by a Multi-Dimensional Approach

Abstract

As water is utilized in various ways across the whole spectrum of human life, better understanding of water management effectiveness and sharing of information and experience are crucial for achieving sustainability from a water perspective. However, water management effectiveness in the long term has been insufficiently studied due partially to the lack of long term data and methodology for long term assessment. The present study presents a case study, dealing with the environmental restoration of a once listed as the worst lake in Japan for 27 years through a water diversion project. It highlights the need and importance of evaluating water management practice from both chemical and biological dimensions for its long-term effectiveness. By combining field surveys of phytoplankton communities and E. coli at multiple locations in the lake in different seasons and data analysis of long term change of chemical parameters of water quality, it revealed that although the diversion project led to a shift in phytoplankton community structure from being bluegreen algae dominated to diatom dominated, the eutrophic level remains high and the diatom-dominated phytoplankton community structure is probably the factor hindering the true recovery of the ecosystem in the lake. Wording differently, the diversion operation alleviated the symptom of eutrophication but did not solve the problem. A message form the present study is that such a multi-dimensional assessment approach allows the explanation of water management effectiveness in ecological relevance and identification of the direction for further improvement work. Therefore, it also serves as a call for the further development of multi-dimensional assessment approaches.

Keywords: water management, long-term assessment, water diversion, Lake Tega, phytoplankton