Papers by Keyword: Catchment

Abstract: Nitrogen and phosphorous pollution is common in China and worldwide. The pollution deteriorates water quality and even causes significant change of the freshwater ecosystem. Management must be strengthened in order to reduce the pollution to secure water supply safety and to maintain healthy ecosystems. This paper investigated the yield of total nitrogen (TN) for different land use types, exemplified in the Xitiaoxi catchment of Lake Taihu basin, where catchment-generated nitrogen pollution is severe. Extensive water quality sampling was performed for different river levels and various land use types. A distributed hydrological model was also employed to simulate the river discharges at locations where flow observation is not available, and the simulated river discharges were used for the calculation of nitrogen yield. It is found that generally the catchment’s nitrogen export is still as high as 2.6 t/km²/year. The yield for forest is 0.8-1.0 t/km²/year, while the yields for arable land and for the river sections immediately downstream of urban area are higher than the average ranging 2.8-3.3 t/km²/year. It is also concluded that the hydrological modelling using a spatially distributed model is helpful and essential in obtaining flows at any locations, which can subsequently be used jointly with the water quality data to identify the critical source areas with high nitrogen yields.

Abstract: Rainwater utilization has great potentials for recovering hydrological cycles, for buffering extreme run-off situations in the watercourses, and for reducing the costs for water supply in urban area. However, little information is available on the water qualities and runoff properties of collected rainwater, which is critical for efficient design and maintenance strategies of rainwater harvesting facilities. In this study, characteristics of rainwater collected in a rainwater harvesting system were examined in terms of pollutant concentrations. Based on these results, TiO2 photocatalysts were applied on the roof surface as a novel coating material to improve the quality of collected rainwater. The analysis of rainwater samples shows that the contamination by turbidity, conductivity, and color occurs during the catchment process, which may result in troubles for further use. The roof coating technique developed in this study appeared to be effective in increasing the wash-off of pollutants and improving the water quality in roof runoff because of its increased hydrophililicy as well as photocatalytic reactivity. Further research is required on trace pollutants such as endocrine disruptors to estimate and minimize health risk in rainwater harvesting.