Showing papers in "Journal of Hydroinformatics in 2002"
TL;DR: In this paper, a model calibration procedure for a municipal-industrial wastewater treatment plant is described step by step, and the importance of different steps is discussed, including a description of the hydraulics in the system via a tracer test, an intensive measuring campaign and supporting lab-scale experiments to obtain and confirm kinetic parameters.
Abstract: The purpose of the calibrated model determines how to approach a model calibration, e.g. which information is needed and to which level of detail the model should be calibrated. A systematic model calibration procedure was therefore defined and evaluated for a municipal–industrial wastewater treatment plant. In the case that was studied it was important to have a detailed description of the process dynamics, since the model was to be used as the basis for optimisation scenarios in a later phase. Therefore, a complete model calibration procedure was applied including: (1) a description of the hydraulics in the system via a tracer test, (2) an intensive measuring campaign and (3) supporting lab-scale experiments to obtain and confirm kinetic parameters for the model. In this paper the model calibration procedure for this case study is described step by step, and the importance of the different steps is discussed. The calibrated model was evaluated via a sensitivity analysis on the influence of model parameters and influent component concentrations on the model output. The sensitivity analysis confirmed that the model output was sensitive to the parameters that were modified from the default parameter values. The calibrated model was finally reduced from a 24 tanks-in-series configuration to a 12 tanks-in-series configuration, resulting in a 50% reduction of the simulation time.
155 citations
TL;DR: Examples presented in the paper show that models explicitly synthesized by genetic algorithms not only perform better in seven-days-ahead predictions of algal blooms than artificial neural network models, but provide more transparency for explanation as well.
Abstract: The paper compares potentials and achievements of artificial neural networks and genetic algorithms in terms of forecasting and understanding of algal blooms in Lake Kasumigaura (Japan) Despite the complex and nonlinear nature of ecological data, artificial neural networks allow seven-days-ahead predictions of timing and magnitudes of algal blooms with reasonable accuracy Genetic algorithms possess the capability to evolve, refine and hybridize numerical and linguistic models Examples presented in the paper show that models explicitly synthesized by genetic algorithms not only perform better in seven-days-ahead predictions of algal blooms than artificial neural network models, but provide more transparency for explanation as well
67 citations
TL;DR: A new approach called Dynamic Identifiability Analysis is presented in order to partly overcome this limitation and a case study shows how the proposed methodology can be applied to increase the identifiability of parameters of a river solute transport model.
Abstract: The use of dynamic mathematical models to simulate the behaviour of environmental systems is common practice. However, the output of these models remains uncertain, despite their widespread use and long history of application. This uncertainty arises, amongst other factors, from errors in the data, randomness in natural processes, incorrect assumptions in the model structure with respect to the processes taking place in the natural system, and the inability of calibration procedures to unambiguously identify an optimal parameter set to represent the system under investigation. The latter two problems may be caused by the inability of the calibration procedure to retrieve sufficient information from the model residuals. In this paper, a new approach called Dynamic Identifiability Analysis is presented in order to partly overcome this limitation. A case study shows how the proposed methodology can be applied to increase the identifiability of parameters of a river solute transport model.
56 citations
TL;DR: It is proposed that a numerical environmental model cannot be justified for predictive tasks without an implicit uncertainty analysis which uses reliable and transparent methods which are shown to converge the parameter distributions to the same end result.
Abstract: It is proposed that a numerical environmental model cannot be justified for predictive tasks without an implicit uncertainty analysis which uses reliable and transparent methods. Various methods of uncertainty-based model calibration are reviewed and demonstrated. Monte Carlo simulation of data, Generalised Likelihood Uncertainty Estimation (GLUE), the Metropolis algorithm and a set-based approach are compared using the Streeter–Phelps model of dissolved oxygen in a stream. Using idealised data, the first three of these calibration methods are shown to converge the parameter distributions to the same end result. However, in practice, when the properties of the data and model structural errors are less well defined, GLUE and the set-based approach are proposed as more versatile for the robust estimation of parametric uncertainty. Methods of propagation of parametric uncertainty are also reviewed. Rosenblueth’s two-point method, first-order variance propagation, Monte Carlo sampling and set theory are applied to the Streeter–Phelps example. The methods are then shown to be equally successful in application to the example, and their relative merits for more complex modelling problems are discussed.
54 citations
TL;DR: In this paper, a planning support system was developed and applied to support policy formulation for rehabilitation of the natural environment in the Western Mancha region in Spain, based on a framework developed for planning and decision making, and includes three main components, namely, a water balance model of the groundwater basin, a planning model and an evaluation model.
Abstract: To support policy formulation for rehabilitation of the natural environment in the Western Mancha region in Spain, a planning support system was developed and applied. The system is based on a framework developed for planning and decision making, and includes three main components, namely, a water balance model of the groundwater basin, a planning model and an evaluation model. The water balance model, which makes use of GIS and remote sensing, simulates the average yearly recharge of the aquifer system in relation to the land use changes for average meteorological conditions, to help understand the current situation; the planning model, which makes use of mixed integer programming, simulates the reaction of farmers towards the changes in the present subsidy schemes and helps formulate a proper policy instruments; and finally the evaluation model, which makes use of multicriteria decision analysis to support the evaluation of developed policies and selection of attractive scenarios based on the identified criteria and the preferences/opinion of various decision makers.
43 citations
TL;DR: A computational methodology that is designed to serve as a watershed decision support system and is capable of controlling environmental impacts of non-point source pollution resulting from erosion and has the potential to improve comprehensive watershed management.
Abstract: The comprehensive and systematic management of watersheds is essential for reducing the adverse environmental impacts arising from anthropogenically caused erosion and subsequent sedimentation. This paper describes a computational methodology that is designed to serve as a watershed decision support system and is capable of controlling environmental impacts of non-point source pollution resulting from erosion. In the decision process, the methodology also accounts for other inseparable objectives such as economics and social dynamics of the watershed. This decision support tool was developed by integrating a comprehensive hydrologic model known as SWAT and state-of-the-art multiobjective optimization technique within the framework of a discrete-time optimal-control model. Strength Pareto Evolutionary Algorithm (SPEA), a multiobjective optimizer based on evolutionary algorithms, has been used to generate Pareto optimal sets. For demonstration purposes, the tool was applied to the Big Creek watershed located in Southern Illinois. Results indicate that the methodology is highly effective and has the potential to improve comprehensive watershed management.
33 citations
TL;DR: In this paper, a mathematical model is applied to the tank of Kipseli in Athens, Greece, which is used for storage, balancing and emergency chlorination, and four alternative arrangements of guiding walls are examined by the model.
Abstract: A mathematical model is applied to the tank of Kipseli in Athens, Greece, which is used for storage, balancing and emergency chlorination. A Flow-Through Curve (FTC) experiment is performed for the initial geometry of the tank. The shape and the characteristics of the FTC show a very poor hydraulic efficiency, with extensive short-circuiting, intense mixing and low detention times. To improve the hydraulic efficiency of the tank the use of four alternative arrangements of guiding walls is examined by the model. Prior to its application, the model is verified by comparing the predicted FTC with the experimental. A satisfactory agreement is observed between the calculated and the experimental curves. Then the model is applied to calculate the flow field and the FTC for the four arrangements. Calculations are compared and the arrangement which shows the highest hydraulic efficiency is proposed for construction.
30 citations
TL;DR: In this paper, a method is presented that uses GIS vector objects with equations assigned for the calculation of time of concentration or lag time for use in hydrologic analysis and design.
Abstract: Synthetic unit hydrographs are commonly used to estimate runoff from rainfall events in a hydrologic analysis. A key parameter required as part of any hydrologic analysis using a synthetic unit hydrograph is time of concentration or lag time. Generally, equations used to compute time of concentration or lag time are empirically derived from basin parameters such as area, slope, and a specific flow path length. A more realistic method for determination of flow path travel time is to divide the flow path according to different hydraulic conditions such as sheet flow, shallow concentrated flow and open channel flow as specified in the NRCS method using TR55. Such equations are all based on flow length and the slope of the flow path, two parameters that are easily calculated from GIS vector objects. A method is presented that uses GIS vector objects with equations assigned for the calculation of time of concentration or lag time for use in hydrologic analysis and design.
29 citations
TL;DR: In this paper, the authors present an optimization approach to wastewater systems planning at regional level, which applies only to sanitary sewer networks and uses simulated annealing algorithm to solve the optimization model upon which the approach is based.
Abstract: A regional wastewater system planning problem consists of finding the minimum-cost configuration for the system needed to drain the wastewater produced at the communities located within a region, while meeting the quality standards defined for the receiving water bodies and complying with all (other) relevant regulatory aspects. There are several possible solutions to this kind of problem. They range from solutions where each community treats its wastewater separately, to solutions where all the wastewater produced in the region is sent to a single treatment plant. It is likely that the most effective solution both in terms of public expenditure, equipment reliability, and environmental impact will be found somewhere between these two extremes. This paper presents an optimization approach to wastewater systems planning at regional level. The approach applies only to sanitary sewer networks. A simulated annealing algorithm is used to solve the optimization model upon which the approach is based. For the application of this approach a user-friendly computing tool was developed. Within this tool, both the acquisition of data and the output of results are made through a flexible GIS interface.
28 citations
TL;DR: How and why Open Source is of particular interest in the field of hydroinformatics is explored, and it is argued that for technical, scientific and business reasons, Open Source has a lot to offer.
Abstract: Open Source, in which the source code to software is freely shared and improved upon, has recently risen to prominence as an alternative to the more usual closed approach to software development. A number of high profile projects, such as the Linux operating system kernel and the Apache web server, have demonstrated that Open Source can be technically effective, and companies such as Cygnus Solutions (now owned by Red Hat) and Zope Corporation have demonstrated that it is possible to build successful companies around open source software. Open Source could have significant benefits for hydroinformatics, encouraging widespread interoperability and rapid development. In this paper we present a brief history of Open Source, a summary of some reasons for its effectiveness, and we explore how and why Open Source is of particular interest in the field of hydroinformatics. We argue that for technical, scientific and business reasons, Open Source has a lot to offer.
26 citations
TL;DR: In this paper, the authors deal with modelling and identification of a river system using physical insights about the process, experience of operating the system and information about the system dynamics shown by the physical insights.
Abstract: This paper deals with modelling and identification of a river system using physical insights about the process, experience of operating the system and information about the system dynamics shown by ...
TL;DR: In this paper, a comparison of the quality modelling tools of the commercial urban drainage software packages HydroWorks (Wallingford Software, UK) and Mouse (DHI, Denmark) reveal important differences between, and incompatibilities in, both models.
Abstract: One of the key aspects in urban drainage (water quality) modelling is the accurate simulation of the input into such models. The modelling of surface sediment build-up, erosion and wash-off is discussed in this paper. An analysis and a comparison of the quality modelling tools of the commercial urban drainage software packages HydroWorks (Wallingford Software, UK) and Mouse (DHI, Denmark) reveal important differences between, and incompatibilities in, both models. The analysis is performed using concentration–duration–frequency (CDF) relationships. A generalised model, accounting for the common model principles used in both models and incorporating the model principles lacking, is proposed.
TL;DR: In this article, the issues involved in such US corporate technology transfers are discussed by way of two examples selected from the activities of the Hydrologic Research Center, a non-profit-making public-benefit research and technology transfer corporation in San Diego, California, USA.
Abstract: Corporate technology transfer by US non-governmental organizations with the substantial involvement of university faculty is a new activity in hydrometeorology The issues involved in such US corporate technology transfers are discussed by way of two examples selected from the activities of the Hydrologic Research Center, a non-profit-making public-benefit research and technology transfer corporation in San Diego, California, USA The projects discussed are: (a) the development and implementation of a robust state estimator for national use within the US National Weather Service River Forecast System, and (b) the development and implementation of a prototype multi-sensor rainfall forecasting system for the Panama Canal Authority The issues covered include technical ones associated with improving theoretical formulations for robust operational performance, those associated with the necessary reciprocal education between modellers and field personnel, and the accommodation of the educational objectives of participating postdoctoral associates
TL;DR: A quasi-optimum irrigation season calendar based on economic profit maximization for sloping and runoff-free furrows can be obtained by OPTIMEC (EConomic OPTIMization, in Spanish), a seasonal furrow irrigation model based on the concept of comprehensive irrigation as discussed by the authors.
Abstract: A quasi-optimum irrigation season calendar based on economic profit maximization for sloping and runoff-free furrows can be obtained by OPTIMEC (EConomic OPTIMization, in Spanish), a seasonal furrow irrigation model based on the concept of comprehensive irrigation. The model features four components: a soil moisture model, an irrigation hydraulic model, a crop yield model and an economic optimization module. This module uses a Genetic Algorithm (GA), a heuristic technique based on the laws of natural selection, to maximize farmer profit. The GA is a suitable technique to solve the problem of profit maximization due to the difficulties inherent in traditional optimization procedures, which require an explicit function relating flow rate, water depth and profit. For its practical application the model has been implemented in a Visual Basic program. A real case is analysed to compare the irrigation season scheduling using traditional criteria (event by event scheduling) and optimization-based criteria.
TL;DR: This work proposes a new formulation of the methodology of the studies in the design phase of wastewater sewerage studies and relies on decision-making support which borrows concepts from expert systems and multicriteria analysis in order to structure the reasoning process and to take into account the very different criteria a real decision- making task often implies.
Abstract: Today, more and more French communities have a critical point of view concerning the performance of their wastewater sewerage systems. The main reason is linked to the methodology of the studies in the design phase. The process is neither adapted to the complexity of the decision-making task, nor to a general management of the wastewater sewerage in a territory. In order to make these studies more coherent and the choices more rational, we propose a new formulation of the methodology as an alternative to the current one. Our approach relies on decision-making support which borrows concepts from expert systems and multicriteria analysis in order to structure the reasoning process and to take into account the very different criteria a real decision-making task often implies. We show that this support has to be interactive and iterative in order to ensure that coherent and relevant solutions are chosen.
TL;DR: In this paper, the hydrodynamic behavior of electrochemical reactors was analyzed by simulating stimulus-response experiments with a simple experimental arrangement to generate data (Residence Time Distribution (RTD) curves) from electrolytic conductivity measurements.
Abstract: This paper analyses the hydrodynamic behaviour of electrochemical reactors by simulating stimulus–response experiments. The experiments were performed with a simple experimental arrangement to generate data (Residence Time Distribution (RTD) curves) from electrolytic conductivity measurements. The multiparametric model proposed and the Matlab program developed allow the study of electrochemical reactors using three-dimensional electrodes, providing values of characteristic parameters of the materials, such as porosity and compressibility. The study of the reactor also permits modelling of the electrochemical reactions that will be produced inside it.
TL;DR: In this article, interactive methods to easily create these structures in grids used by numerical models are presented that show great promise in reducing the time and effort required to consider multiple scenarios for modelling and management.
Abstract: Applying numerical modelling techniques to surface water bodies often requires the addition of man-made structures such as embankments or dredged shipping lanes to the natural bathymetric conditions. The application of the model may be to determine the specifications of these structures, such as size and location. Therefore, multiple variations of the structure must be evaluated. Interactive methods to easily create these structures in grids used by numerical models are presented that show great promise in reducing the time and effort required to consider multiple scenarios for modelling and management. The methods presented utilize a conceptual representation of the domain. Features in this conceptual model are used to derive grid elements for the numerical model. The resulting numerical models provide information for decision support based on multiple design considerations.
TL;DR: The conceptual user interface requirements of the Land Management System (LMS), a next-generation system designed to support the development of location-specific landscape/watershed management oriented simulation models, are explored.
Abstract: This paper explores the conceptual user interface requirements of the Land Management System (LMS), a next-generation system designed to support the development of location-specific landscape/watershed management oriented simulation models. Currently available landscape/watershed models tend to be discipline-specific, focusing only on hydrology, ecology, social, economic or agronomic aspects of the landscape's subsystems. Feedback loops among the different subsystems tend be ignored, and this can result in long-term predictions that may not be useful. LMS will provide landscape and watershed managers with sets of software modules that can be linked together to represent and simulate unique local conditions. A design challenge of LMS is to develop a user interface that makes it possible for a watershed/landscape manager to develop and use multidisciplinary spatially explicit landscape simulation models that retain the scientific rigour of current scientist-oriented simulation models. This paper outlines a solution in response to that challenge.
TL;DR: In this paper, a method was developed to estimate turbulent dispersion based on fuzzy rules that use local transverse velocity shears to predict turbulent velocity fluctuations in open-channel dead zones.
Abstract: A method has been developed to estimate turbulent dispersion based on fuzzy rules that use local transverse velocity shears to predict turbulent velocity fluctuations. Turbulence measurements of flow around a rectangular dead zone in an open channel laboratory flume were conducted using an acoustic Doppler velocimeter (ADV) probe. The mean velocity and turbulence characteristics in and around the shear zone were analysed for different flows and geometries. Relationships between the mean transverse velocity shear and the turbulent velocity fluctuations are encapsulated in a simple set of fuzzy rules. The rules are included in a steady-state hybrid finite-volume advection–diffusion scheme to simulate the mixing of hot water in an open-channel dead zone. The fuzzy rules produce a fuzzy number for the magnitude of the average velocity fluctuation at each cell boundary. These are then combined within the finite-volume model using the single-value simulation method to give a fuzzy number for the temperature in each cell. The results are compared with laboratory flume data and a computational fluid dynamics (CFD) simulation from PHOENICS. The fuzzy model compares favourably with the experiment data and offers an alternative to traditional CFD models.
TL;DR: In this paper, the authors proposed the basic ideas used in simulations for two planned regional waste material depositories, a planned sewage sludge composting plant and an active aluminium dross depository of a foundry.
Abstract: Damage of the waterproofing system in a waste material depository or sewage sludge composting plant and the penetration of pollutants into the soil and groundwater may cause an environmental mishap. Although the standard waterproofing technologies are extremely safe, one cannot disregard possible malfunctions. For a well-established plan of managing unexpected events, the impact of such damage must be forecast. With the help of models described in the relevant literature, we propose the basic ideas used in simulations for two planned regional waste material depositories, a planned sewage sludge composting plant and an active aluminium dross depository of a foundry.
TL;DR: Fuzzy rules are used to model solute dispersion in a river dead zone, such that the turbulent diffusion is determined by a fuzzy inference system which relates the local mean velocity shear to the longitudinal velocity fluctuations as mentioned in this paper.
Abstract: Fuzzy rules are used to model solute dispersion in a river dead zone, such that the turbulent diffusion is determined by a fuzzy inference system which relates the local mean velocity shear to the longitudinal velocity fluctuations. A finite-volume hybrid scheme is applied to a non-orthogonal grid for which a mean velocity field is produced using the computational fluid dynamics (CFD) package Telemac 2D. At each cell face fuzzy rules predict a fuzzy number, and these numbers reflect the possible magnitudes of turbulent velocity fluctuations. These are input to the finite-volume model using a single-value simulation method. Multiple model runs produce a fuzzy number for the solute concentration in each cell. The results of the fuzzy model are then compared with data collected in a field experiment with rhodamine dye in the River Severn.