Trend Analysis In The Application Of Water Quality Management Research

As the basis of water quality management and planning, the water quality trend analysis has been paid more and more attention. In this filed, our country started late, we usually use simple and visual chart to express, but seldom use multiple statistic method and trend statistical method. Moreover, the application of trend analysis in water quality management has not been systematically reported. This study systematically reviewed the commonly used methods in water quality management, such as the LOWESS smoothing, the Daniel’s trends test, the nonparametric Mann-Kendall’s test and Sen’s method, the seasonal Kendall’s test at al, in order to supply a theoretical reference for other researches on water quality management. Meanwhile, we take Haihe and Yuqiao reservoir for examples to examine the feasibility and availability of trend analysis methods applied in water quality management of river and reservoir.At present, there has been a lot of research on the organic pollution, eutrophication pollution, and heavy metals pollution of the Haihe River. However the research on its water pollution trend has not been common. Water quality trends of of the Haihe River (the urban section in Tianjin) were determined with the application of the LOWESS smoothing and Daniel’s trend test for five parameters-chloride(Cl), dissolved oxygen(DO), biochemical oxygen demand(BOD), chemical oxygen demand (CODMn), and ammonia nitrogen(NH3-N) between1986and2005. The result showed that in the five water quality parameters only DO could meet the grade-Ⅱ of Environmental quality standards for surface water, COD reached the grade-IV, BOD andNH3-N changed a lot and reached the grade-Ⅳ on average, but NH3-N reached the grade-Ⅴ in some years. The values of Cl were more than the centralized drinking water standards every year, up to five times mostly. On the whole, the water quality got worse and then tended to be good over the last20years. Cl and BOD increased slightly, COD increased significantly (Rs=0.4075,a<0.05). While DO increased very significantly (Rs=0.5320,a<0.01). Moreover NH3-N declined. This shows that during the Tenth Five-Year Plan of the Haihe River Basin Water Pollution Control, the total control of pollutant emissions, the total control of pollutants into the river, the establishment of a large number of sewage treatment projects that were carried out in Tianjin, and other series of the Haihe governance project and measures had achieved positive and effective results.Water quality trends and eutrophication degree of Yuqiao Reservoir has become the focus of attention, which not only directly affects the development of Tianjin’s industry and agriculture, but also relates to the health of people, the domestic water security, and the water quality of Luanhe-Tianjin Water Diversion Project.Due to the lack of seasonal water quality monitoring data,water quality trends at the Yuqiao Reservoir in Tianjin were determined with the application of a non-parametric Mann-Kendall’s test for five parameters-pH, DO, BOD, CODMn, and NH3-N between1986and2005. And the magnitude of the trend was calculated with the nonparametric Sen’s method. The result showed that water quality of the Yuqiao Reservoir could meet the grade-Ⅲ of Environmental quality standards for surface water over the last20years, pH, DO, BOD andNH3-N reached the grade-Ⅱ, but COD reached the grade-Ⅲ. On the whole, the water quality tended to be stable, but DO declined and COD increased significantly, and a significant negative correlation between DO and COD was found. pH increased slightly, and there are no significant trends in BOD and NH3-N. As the industrialization and urbanization had been accelerating in the surrounding area of the reservoirs and the upper reaches, and with the rapid growth of population, there were no significant changes of the water quality, which indicated that integrated practice measures of water quality adopted for many years had achieved certain results.