Nowadays, nonpoint source pollution has been a dominant cause of water quality deterioration and eutrophication. For large basins, long-term effects of ecological factors on nonpoint source pollution are significant and have gained worldwide attention. Yangtze River is the largest river in China, and water environment protection of its upper reach is crucial to maintain the whole river health and the Three Gorges Project successful operation. The objective of this study is to reveal the effects of ecological factors on nonpoint source pollution in the upper reach of the Yangtze River during the period from 1960 through 2003 by the Improved Export Coefficient Model and the Nutrient Losses Empirical Model. The results indicated that during those decades the effects of ecological factors on dissolved pollutants were constant whereas those on sediment as well as absorbed pollutants changed slightly and decreased obviously after 2000. Comparing to anthropogenic factors, ecological ones had a dominant influence on sediment and absorbed pollutants. As for load intensities, long-term effects of ecological factors on dissolved pollutants hadn't changed much, while those on sediment as well as absorbed pollutants was increasingly significant and then reached an ultimate in 1980. Atmospheric deposition, grassland as well as forest were important sources of dissolved nitrogen export, nevertheless, grassland and forest were the main export areas of dissolved phosphorus, sediment as well as absorbed pollutants. The study would facilitate the source identification and nonpoint source pollution control in the upper reach of the Yangtze River to improve water quality.

Nowadays, the effects of water pollution accidents on water quality safety and regional residents' living have attracted worldwide attention. Therefore, the objective of this research is to propose an early warning and forecasting model and develop a visual system of water quality safety for drinking water source areas in the Three Gorges Reservoir Area under accident conditions. Based on an Instantaneous Point Source Two-dimensional Water Quality Model and the security requirements of water quality, an early warning and forecasting model was presented, and then the system was advanced by a MATLAB platform. In addition, a hypothetical case was also carried out for the Fenghuangshan drinking water source area. Within 0.040 h to 0.096 h after the accident, the water quality could meet the standard, and the warning level was primary and intermediate, sequentially. From 0.096 h to 11.960 h after the accident, the pollutant concentration exceeded the standard, under which conditions advanced warning started. Then the intermediate and primary warnings restarted in sequence until the pollutant concentration decreased to the background value. Therefore, the proposed model could accurately predict the spatial-temporal change trend of pollutant concentration, and the developed system could efficiently realize early warnings and the forecasting of water quality safety.

Abstract:The upper reach of the Yangtze River is an ecologically sensitive region where water loss, soil erosion, and nonpoint source (NPS) pollution are serious issues. In this drainage area, regosol is the most widely distributed soil type. Cultivation on regosol is extensive and total nitrogen (TN) has become a common NPS pollutant. Artificial rainfall experiments were conducted to reveal the influence mechanisms of rainfall and terrain on TN losses from regosol. The results showed that there were positive correlations between precipitations and TN loads but negative ones between precipitations and TN concentrations. Furthermore, negative correlations were more obvious on fields with slopes of 5 • and 25 • than on other slopes. With increasing rainfall intensity, TN loads rose simultaneously. However, TN concentration in runoff-yielding time presented a decline over time. As far as terrain was concerned, TN loads grew generally but not limitlessly when slopes increased. Similarly, TN concentrations also rose with rising slopes; upward trends were more obvious for steeper slopes. Furthermore, the initial runoff-yielding time became longer for steeper slopes and the differences under various rainfall intensity conditions diminished gradually.

No abstract

No abstract