In this study, the Hydrological Simulation Programme‐FORTRAN (HSPF) and the Water Quality Analysis Simulation Programme (WASP), were adopted as a combined tool. The long Feitsui impounding reservoir located in Taiwan was used as a case study. The combined model helped illustrate the total phosphorus (TP) mass balance. Approximately 51.4% of the TP flowed out from the reservoir, while 16.2% of the TP remained in the waterbody and 32.2% of the TP was deposited. The reservoir was divided into five sections along its length for a quality analysis. The exceedance probability (the probability of exceeding the eutrophic level, i.e., TP = 24 μg/L) was 9.7% in the upstream section. If the TP load increased by 20%, the eutrophication exceedance probability could increase to 25.5%. This study demonstrated the usage of the combined model tool and the exceedance probability method in the data analysis, which could guide effective catchment management and eutrophication risk prevention.

Night markets are attractive tourist sites in Asian cities. However, the outdoor activities produce different types of pollutants. Air pollution and solid waste in night markets have received much attention, but wastewater pollution from night markets has rarely been examined. The untreated wastewater are discharged into roadside gutters and might contaminate receiving waterbodies. In this study, night markets in Taipei city, Taiwan, were surveyed to clarify the characteristics of wastewater. The sampled wastewater showed high levels of organic substances, oil and grease, and phosphorous but low levels of nitrogen compounds. In addition, the unit pollution loads in night market stalls was obtained. The BOD load of each stall in the night markets was 2,509 g/day, which is higher than the sewage emissions of 50 people. In order to know the impacts of night market wastewater on receiving waterbody, a water quality model, the Water Quality Analysis Simulation Program (WASP), was used in the studied river, Keelung river. If night market wastewater could be collected (not discharged), the BOD concentration could be reduced by 9.8%, but the NH3-N and DO concentration could be reduced by less than 1%.

Infrastructures (public constructions) are necessary for people’s lives, but large infrastructures can be harmful to local ecosystems and wildlife. The ecological mitigation practices of more than 5000 public construction projects in Taiwan were reviewed. Among these cases, the reduction practices were 38%–58%, and the avoiding, minimizing, and compensation measures were nearly 20%. However, the number of statistical measures did not reflect the actual performance. This study developed a quick and operational assessment framework to assess ecological mitigation measures. The four indicators were ecological concern areas, number of ecological conservation measures, number of ecological conservation objects, and habitat quality. The assessment indicators were applied to 54 construction cases, and their performance was classified into excellent, good, fair, and qualified. The developed assessment indicators were proven capable of serving as a preliminary tool to determine the performance of ecological mitigation practices, and the criteria standard can be adjusted as cases are updated.

Low-impact development (LID) structures are widely used to mitigate urbanization impacts on hydrology. The performances of such structures are strongly affected by field conditions, such as the ratio of LID area to drainage area and rainfall properties, such as rainfall intensity. In this study, onsite continuous monitoring was performed at a permeable pavement site and a raingarden site in Taipei, Taiwan, to determine their water retention and groundwater recharge potential under subtropical weather. In addition, the verified Storm Water Management Model (SWMM) was used to illustrate the annual performance on the hydrological cycle. Based on one year of monitoring, data on 41 and 24 rainfall events were obtained at the permeable pavement and raingarden sites, respectively. The ratio of the permeable pavement area to the total drainage area was 36.0%, and this ratio was 15.9% for the raingarden. The results showed that the average runoff reduction rate was 14.7% at the permeable pavement site, and 98.3% of the rainfall was retained in the raingarden and an underground storage tank. The validated model showed that the permeable pavement site experienced 45.3% outflow, 31.6% evaporation, and 23.1% infiltration annually. For the raingarden with an underground storage tank, 91.4% of the annual rainfall infiltrated and was stored, with only 4.1% outflow. According to the observed rainfall event performance and the simulated annual performance, the permeable pavement and raingarden performed well in subtropical regions. Pavement that was approximately 1/3 permeable in a drainage area increased infiltration by approximately 20%, and a raingarden with a sufficient underground storage tank preserved over 90% of the rainfall.

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