AMWRUC · modelling of integrated water systems under uncertainty for aquatic environment rehabilitation in rapidly urbanised catchments

modelling of integrated water systems under uncertainty for aquatic environment rehabilitation in rapidly urbanised catchments

Project context and objectives Many catchments in developing countries are undergoing rapid urbanisation, in which water systems become a fusion of social factors, economical factors and elements, man-made water features and natural water bodies. Modelling of these water systems poses a significant challenge and requires a change in thought paradigm in order to deal with rapid spatial-temporal changes in the physical elements and the associated catchment responses. AMWRUC (PIIF-GA-2008-220448) is a project with an aim to develop a novel framework of approach for modelling such integrated water systems, subjected to rapid changes over a relatively short period of time. Project results The project was divided into the ‘incoming phase’ and the ‘return phase’. The incoming phase (from October 2008 to September 2010) has been completed and the main results achieved are listed and described below. 1. Impact of land-use on water pollution in a rapidly urbanising catchment The Identification of unit Hydrographs And Component flows from Rainfall, Evaporation and Streamflow data (IHACRES) model, the pollutant build-up and wash-off model, and the Generalized Likelihood Uncertainty Estimation (GLUE) method were integrated to simulate rainfall-runoff pollution under uncertainty. Furthermore, the model was applied to evaluate the impact of the heterogeneous composition of land-use on water pollution in the Shiyan reservoir catchment. The results indicated that pollutant-load generation and runoff-water quality have strong positive spatial correlation with the proportion of residential land use. It can be deduced that residential land-use type is the most important source of runoff pollution and thus most attention should be paid to this land-use type in runoff-pollution control. 2. Effect of water exchange on eutrophication in landscape water bodies A US Environmental Protection Agency Water Quality Analysis Simulation Program (EPA WASP) model for eutrophication in landscape water bodies was calibrated and validated based on experimental data. Then the model was applied to evaluate the effect of water exchange on chlorophyll-a growth in the landscape water body supplemented by treated wastewater. The results indicate that water exchange has both a dilution process to decrease the algae level and a nutrient-supply process to increase the algae level. The two processes initially cause the algae level to rise, and then decline as the hydraulic resident time (HRT) increases, and HRT has a critical point at which the pond faces the highest risk of algal boom. Therefore, the critical HRT should be avoided in landscape pond water management.3. Framework of model for integrated water system in a rapidly urbanising catchment A coupled System Dynamics and Water Environmental Model (SyDWEM) was developed to improve the understanding of the integrated socio-economic and water management system in a rapidly urbanising catchment. The Shenzhen River catchment was used as a case study to demonstrate usage of the functionality and purpose of the integrated model. The SyDWEM was further applied to assess the effect of the proposed measures on environmental and development indicators in the catchment for the next 10 years (2011 to 2020). It can be demonstrated that SyDWEM has the capacity to evaluate the effects of both socio-economic and engineering measures on GDP and population growth, the balance of water resources, and water quality in the river; it also provides a tool for integrated decision-making to be used by economists, urban planners and water-infrastructure designers. 4. Multi-objective optimisation models of water systems in rapidly urbanised catchments A multi-objective optimisation approach with integrated wastewater-treatment cost function, dynamic water-quality model and Non-dominated Sorting Genetic Algorithm II (NSGA-II) was developed for water-pollution control in a tidal river with significant temporal and spatial variations in water quality. The case study of the Shenzhen River catchment indicated that the Pareto optimal solutions based on this approach can wholly illustrate the trade-off relationships between objectives. This approach can also provide support in decision-making with regard to water-pollution control in tidal river catchments. Conclusion In conclusion, an innovative approach for the modelling of integrated water systems in rapidly urbanising catchments has been successfully developed. The approach allows decision-makers to investigate the feasibility of different catchment-rehabilitation measures within a common platform, for better comparison and sounder judgments. Several case studies from Shenzhen, an emerging city on the rapidly urbanising southeast coast of China, have been carried out to demonstrate the reliability and effectiveness of this approach. Potential impact and use The proposed modelling method for water systems in this research will provide an effective decision-making support tool for integrated water management in developing countries. Application of this method will help ease the conflict between socio-economic development and aquatic-environment protection, and will further boost the sustainable socio-economic development in those applied areas. The results of the case studies in the catchments of the Shenzhen River and Shiyan Reservoir (upstream of the Maozhou river), both in China, will be circulated to local government bodies (e.g. Shenzhen Municipal Water Affairs Bureau and Shenzhen Environment Protection Bureau), and will hopefully also be distributed to other rapidly urbanising catchments around the world. References Qin H.P., Su Q., Khu S.T., Yu X.Y. (2011) An integrated model for water management in a rapidly urbanizing catchment. Environmental Modelling & Software. 26 (2011) 1502-1514, doi:10.1016/j.envsoft.2011.07.003 Qin H.P., Khu S.T., Yu X.Y. (2010) Spatial variations of storm runoff pollution and their correlation with land-use in a rapidly urbanizing catchment in China. Science of the Total Environment. 408:4613–4623, doi:10.1016/j.scitotenv.2010.07.021.

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