Improving Run Time in Three-Dimensional Reservoir Hydrodynamics and Water Quality Modeling

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Improved dynamic emulation modeling by time series clustering: The case study of Marina Reservoir, Singapore

Dynamic Emulation Modelling (DEMo) is emerging as a viable solution to combine computationally intensive simulation models and dynamic optimization algorithms. A dynamic emulator is a low order surrogate of the simulation model identified over a sample data set generated by the original simulation model itself. When applied to large 3D models, any DEMo exercise does require a pre-processing of the exogenous drivers and state variables in order to reduce, by spatial aggregation, the high number of candidate variables to appear in the final emulator. This work describes a hybrid clustering-variable selection approach to automatically discover compact and relevant representations of high-dimensional data sets. Time series clustering is adopted to identify spatial structures by objectively organizing data into homogenous groups, where the within-group-object similarity is minimized. In particular, the proposed approach relies on a hierarchical agglomerative clustering method, which starts by placing each time-series in its own cluster, and then merges clusters into larger clusters, until a compact, yet informative, representation of the original variables can be processed with the Recursive Variable Selection - Iterative Input Selection algorithm, in order to single out the most relevant clusters. The approach is demonstrated on a real-world case study concerning the reduction of Delft3D, a spatially distributed hydrodynamic model used to simulate salt intrusion dynamics in the tropical lake of Marina Reservoir, Singapore. Results show that the proposed approach permits a parsimonious, though accurate, characterization of salinity concentration

Temporal variation of faecal indicator bacteria in tropical urban storm drains

Human faecal contamination poses a widespread hazard for human health. In urban areas, sewer leakage may be an important cause of faecal pollution to surface water. Faecal indicator bacteria (FIB) are the most widely used indicators to monitor surface water quality. However, assessing whether a water body is meeting water quality criteria is made difficult by the high variability of FIB concentrations over time. In this study, the variation of FIB concentration in surface water from tropical urban catchments is investigated. Eleven urban sub-catchments were sampled hourly over 24-hr and samples analysed for FIB. It was found that FIB show a diurnal pattern that is characterised by daytime FIB concentrations that are significantly higher than nighttime FIB concentrations. This observed diurnal variation of FIB closely follows that of sewer flows and contrasts with observations in rural streams where FIB concentrations are known to be low in the daytime and high during the night. Field tracer tests provide qualitative evidence of sewage exfiltration and transport to drains via preferential flow paths. The diurnal FIB variation and field tracer tests indicate the likelihood of surface water contamination due to leaking sewers. The results further suggest that contamination of surface-water drains is likely a widespread problem in tropical urban areas due to extensive drainage networks and the persistence of FIB under tropical conditions. Because of FIB variation over time, the time at which samples are collected is important in being able to capture the daily maximum and minimum FIB concentrations. The Kruskal–Wallis test shows that hourly sampling from 04:00 to 07:00 and from 12:00 to 15:00 results in significantly different FIB concentration (minimum and maximum, respectively). Furthermore, the Wilcoxon-Mann-Whitney test shows that sampling at 12:00 and 14:00 results in significantly higher FIB concentrations, while sampling at 05:00 and 04:00 or 05:00 and 06:00 results in significantly lower FIB concentrations, than sampling at other hours of the day.NRF (Natl Research Foundation, S’pore)Accepted versio

Improved dynamic emulation modeling by time series clustering: The case study of Marina Reservoir, Singapore

iEMSs 2012 - Managing Resources of a Limited Planet: Proceedings of the 6th Biennial Meeting of the International Environmental Modelling and Software Society317-32

Associations of chemical tracers and faecal indicator bacteria in a tropical urban catchment

Surface water contamination by human faecal wastes is a widespread hazard for human health. Faecal indicator bacteria (FIB) are the most widely used indicators to assess surface water quality but are less-human-specific and have the potential to survive longer and/or occur naturally in tropical areas. In this study, 13 wastewater chemicals (chloride, boron, orthosphophate, detergents as methylene blue active substances, cholesterol, cholestanol, coprostanol, diethylhexyl phthalate, caffeine, acetaminophen, ibuprofen, sucralose and saccharin) were investigated in order to evaluate tracers for human faecal and sewage contamination in tropical urban catchments. Surface water samples were collected at an hourly interval from sampling locations with distinct major land uses: high-density residential, low-density residential, commercial and industrial. Measured concentrations were analysed to investigate the association among indicators and tracers for each land-use category. Better correlations were found between different indicators and tracers in each land-use dataset than in the dataset for all land uses, which shows that land use is an important determinant of drain water quality. Data were further segregated based on the hourly FIB concentrations. There were better correlations between FIB and chemical tracers when FIB concentrations were higher. Therefore, sampling programs must be designed carefully to take the time of sampling and land use into account in order to effectively assess human faecal and sewage contamination in urban catchments. FIB is recommended as the first tier in assessment of surface water quality impairment and chemical tracers as the second tier. Acetaminophen and coprostanol are recommended as chemical tracers for high-density residential areas, while chloride, coprostanol and caffeine are recommended for low-density residential areas

Applying Landscape Ecology in Local Planning, Some Experiences

Landscape ecology is repeatedly described as an applied science that can help reduce the negative effects of land-use and land-use changes on biodiversity. However, the extent to which landscape ecology is in fact contributing to planning and design processes is questioned. The aim of this paper is to investigate if and how landscape ecology can be integrated in a planning and design process, and to uncover possible problems that, e.g., landscape architects and planners, may face in such processes. Our conclusion, based on a case study from Asker municipality, Norway, is that such a landscape ecological approach has a lot to offer. However, it is difficult to exploit the potential fully for different reasons, e.g., biodiversity information tends to be specialized, and not easily used by planners and designers, and landscape ecological principles need an adaptation process to be applicable in a real-world situation. We conclude that for the situation to improve, landscape ecologists need to ease this process. In addition, we recommend collaboration across disciplinary boundaries, preferably with a common design concept as a foundation