Development And Application Of Retrospective Assessment In Watershed Water Quality Assessment

Most watersheds all over the world are facing environmental issues of increasing population, land use change, point and non-point source pollution etc. With the decline of water quality and shortage of water resources, the sustainable development of socio-economic system in watershed would be affected. As a useful tool to integrated watershed management, the water quality retrospective assessment in watershed (WQRAW) could find out the relation between human activities and environmental changes. It could promote the decision-making in integrated watershed management towards sustainability.Based on the review and comparison of the approaches and methods for water quality assessments, this paper set up a framework of WQRAW, and proposed the approach and methods for it by using trend detection method, factor analysis and regression method etc. The cumulative effect among human activities, natural factors and water quality were discussed. And then the framework was applied into Jiulong River Watershed, Fujian Province, China. The results are as follows:(1) The Framework and approach for WQRAW was set up, which redefined the WQRAW, determined the concept and methods of watershed scale, boundary, assessing units, components and factors, focused on spatio-temporal trend and correlation analysis, cumulative effects and cause-effect analysis, and built the methods of WQRAW including non-parametric statistic test and multiple correlation method according to the characteristic of retrospective assessment(2) The WQRAW system was applied into Jiulong River Watershed. The Results showed that the spatial issues in the regions are not consistent. In the past 20 years, the cumulative effect of water quality was found in the Longyan area of the North River of the Watershed due to the rapidly increasing in livestock-culture. The factors affected water quality have rapidly shifted due to land use change in the Watershed, for example, heavy nitrogen pollution recent years in West River area was mostly caused by the fertilizer used in fruit planting increasing. In addition, the application of the WQRAW was effective by combining trends analysis, correlation analysis and ecological effect etc.The approach and methods for WQRAW were fully established for the first time. It could be applied especially in the watersheds on a small scale.