Showing papers in "Environmental Modelling and Software in 2000"
TL;DR: The steps that should be followed in the development of artificial neural network models are outlined, including the choice of performance criteria, the division and pre-processing of the available data, the determination of appropriate model inputs and network architecture, optimisation of the connection weights (training) and model validation.
Abstract: Artificial Neural Networks (ANNs) are being used increasingly to predict and forecast water resources variables. In this paper, the steps that should be followed in the development of such models are outlined. These include the choice of performance criteria, the division and pre-processing of the available data, the determination of appropriate model inputs and network architecture, optimisation of the connection weights (training) and model validation. The options available to modellers at each of these steps are discussed and the issues that should be considered are highlighted. A review of 43 papers dealing with the use of neural network models for the prediction and forecasting of water resources variables is undertaken in terms of the modelling process adopted. In all but two of the papers reviewed, feedforward networks are used. The vast majority of these networks are trained using the backpropagation algorithm. Issues in relation to the optimal division of the available data, data pre-processing and the choice of appropriate model inputs are seldom considered. In addition, the process of choosing appropriate stopping criteria and optimising network geometry and internal network parameters is generally described poorly or carried out inadequately. All of the above factors can result in non-optimal model performance and an inability to draw meaningful comparisons between different models. Future research efforts should be directed towards the development of guidelines which assist with the development of ANN models and the choice of when ANNs should be used in preference to alternative approaches, the assessment of methods for extracting the knowledge that is contained in the connection weights of trained ANNs and the incorporation of uncertainty into ANN models.
2,181 citations
TL;DR: The software, which recently was rewritten, has been carefully designed to facilitate interaction with other models, either by replacing individual Daisy processes or by using Daisy as a part of a larger system, thus making Daisy an open software system.
Abstract: Daisy is a well tested dynamic model for simulation of water and nitrogen dynamics and crop growth in agro-ecosystems. The model aims at simulating water balance, nitrogen balance and losses, development in soil organic matter and crop growth and production in crop rotations under alternate management strategies. The software, which recently was rewritten, has been carefully designed to facilitate interaction with other models, either by replacing individual Daisy processes or by using Daisy as a part of a larger system, thus making Daisy an open software system.
305 citations
TL;DR: It is shown that the space–time variational approach is able to analyze emission rates of NO directly, for volatile organic compounds (VOC), regularization techniques must be introduced, however.
Abstract: The problem of analyzing the chemical state of the troposphere and the associated emission scenario on the basis of observations and model simulations is considered. The method applied is the four-dimensional variational data assimilation method (4D-var) which iteratively minimizes the misfit between modeled concentration levels and measurements. The overall model–observation discrepancy is measured in terms of a cost function, of which the gradient is calculated for subsequent minimization by adjoint modeling. The model applied is the University of Cologne EURopean Air pollution Dispersion model (EURAD) simulating the meso-alpha scale. The forward and adjoint components are Bott's horizontal and vertical advection scheme (Bott, Mon. Wea. Rev. 117 (1989), 1006), implicit vertical diffusion, and the RADM2 gas phase chemistry. The basic feasibility of the adjoint modeling technique for emission rate assessment is demonstrated by identical twin experiments. The objective of the paper is to demonstrate the skill and limits of the 4D-var technique to analyze the emission rates of non-observed precursor constituents of ozone, when only ozone observations are available. It is shown that the space–time variational approach is able to analyze emission rates of NO directly. For volatile organic compounds (VOC), regularization techniques must be introduced, however.
191 citations
TL;DR: DIFS is further refined and developed into a software tool which both simulates temporal and spatial changes in concentrations of trace metals in solid and solution phases in sediments during in situ DGT deployments, and estimates resupply parameters from experimental data.
Abstract: The technique of Diffusive Gradients in Thin-films (DGT) can measure in situ fluxes of trace metals in sediments. Interpretation of these measurements requires a numerical model of trace metal reaction and transport in sediments. The DIFS (DGT Induced Fluxes in Sediments) model has permitted quantitative interpretation of DGT measurements in terms of fundamental kinetic and equilibrium resupply parameters. DIFS is here further refined and developed into a software tool which both simulates temporal and spatial changes in concentrations of trace metals in solid and solution phases in sediments during in situ DGT deployments, and estimates resupply parameters from experimental data. The basis of the DIFS model is a pair of linked parabolic PDEs describing dissolved and sorbed trace metal concentrations in the sediment and DGT device. These are solved by the Method of Lines using standard ODE solvers. The solutions are processed to obtain the DGT response. The use of the software, in particular the format of the text file containing input parameters, is described. Illustrative examples of the type of behaviour predicted for DGT by DIFS are provided.
189 citations
TL;DR: Analyzing data issues related to the performance of models and how well they match physical landscape conditions concludes that tighter integration between generic sub-models for physical landscape processes and GIS is still required.
Abstract: Modeling the impact of non-point source pollution in catchments is a complex problem, and one that has troubled natural resource managers for many years. The development of spatially distributed hydrologic models has led to improved model forecasting at the cost of requiring more detailed spatial information. In addition, the analysis is much more sensitive to errors in the data. Incorporation of catchment models into a Geographical Information System (GIS) has improved matters by streamlining data input and providing better interpretation of model outputs. This paper reviews different strategies for linking a catchment model with GIS. It examines data issues related to the performance of models and how well they match physical landscape conditions. Integration with GIS is shown to be necessary for the efficient and proper operation of models in resource management situations. The paper concludes that tighter integration between generic sub-models for physical landscape processes and GIS is still required.
130 citations
TL;DR: Weighted Average is concluded that WA is the method of choice when applied within the boundaries of the present study and is ranked based on the consistency of results.
Abstract: A computer program was created to conduct a comparative study of five Multi-Criteria Evaluation Methods (MCEMs), each of which is capable of evaluating alternatives in a resource management setting. The MCEMs included Weighted Average (WA), Preference Ranking Organization METHod for Enrichment Evaluations (PROMETHEE II), Compromise Programming (CP), ELimination and Choice Translating REality (ELECTRE II). and Analytical Hierarchy Process (AHP). In this study, each of the MCEMs is applied to an array of different management alternatives for andromodous fish migration through the Red Bluff Diversion Dam (RBDD) along the Sacramento River in California. Results are evaluated and MCEMs are ranked based on (1) the consistency of results, (2) the amount of interaction required by the user and (3) the degree of usability by technical and nontechnical professionals. It is concluded that WA is the method of choice when applied within the boundaries of the present study.
105 citations
TL;DR: In this article, the Ensemble Kalman Filter (EKF) was used for data assimilation of ground-level ozone measurements in 17 groups of countries, and the main conclusion is that it is possible to improve ATCM simulations of ozone, but that noise inputs other than emissions only are essential for the reduction of the differences between measured and modelled concentrations to acceptable margins.
Abstract: Modelled ozone concentrations often differ from measured concentrations quite substantially, partly due to measurement errors, but mainly due to uncertainties in the model. Modelling studies would therefore benefit highly from more reliable model simulations. One way to achieve this is the application of data assimilation, a technique that uses measurement information within the model simulation in a way that is consistent with the model itself. This aim of this paper is to show that this is indeed one way to go with atmospheric transport chemistry models (ATCMs) by presenting results of data assimilation simulations of ozone with the model LOTOS. The assimilation technique used in this study is the Ensemble Kalman Filter. A simulation for a period of 4 weeks has been performed in which ground-level ozone measurements have been assimilated. The necessary noise input consisted of uncertainties in the emissions of NOx, SOx, VOC and CO in 17 groups of countries. The main conclusion is that it is possible to improve ATCM simulations of ozone by data assimilation, but that noise inputs other than emissions only are essential for the reduction of the differences between measured and modelled concentrations to acceptable margins.
92 citations
TL;DR: This study analyzes, from a modeler's perspective, various coupling methodologies according to their characteristics, and presents a modeling framework for coupled environmental models requiring dynamic feedback during a simulation (e.g., multimedia modeling).
Abstract: Environmental models have been developed to address narrowly defined issues. As these issues become broader and scientific understanding grows, models become more complex. A variety of methodologies couple environmental models to address multifaceted issues, such as cross-media effects, risk analysis, and environmental justice investigations. This study analyzes, from a modeler's perspective, various coupling methodologies according to their characteristics. This analysis is presented as a five-level coupling hierarchy, and includes a representation of a modeling framework for coupled environmental models requiring dynamic feedback during a simulation (e.g., multimedia modeling). The framework addresses the special needs for this type of modeling, including spatial locking for environmental data, autogeneration of simulation metadata, simulation verification, and automated recovery from system problems.
91 citations
TL;DR: VF is aimed at assisting public decision-makers and conservation biologists to assess the viability of endangered and threatened species, to evaluate policies and plans for wildlife management, as well as species translocations, reserve design and habitat protection.
Abstract: A computer program, VVF, has been developed to assess the suitability of a territory as habitat for a species. It integrates several types of Habitat Suitability models into a Geographical Information System. In addition to standard GIS functions, VVF allows a user to create, modify and store new Habitat Suitability models for different species, to create Habitat Suitability maps by running Habitat Suitability models for specific areas, and to process these maps. The program requires only basic GIS knowledge and is very flexible, so as to guarantee a broad applicability. VVF is aimed at assisting public decision-makers and conservation biologists to assess the viability of endangered and threatened species, to evaluate policies and plans for wildlife management, as well as species translocations, reserve design and habitat protection. VVF can also be used in Environmental Impact Assessment. In this paper, VVF is demonstrated with an application for Ibex.
73 citations
TL;DR: The Simulation Network Interface (SNI) is introduced, a software package for easy coordination of different existing simulation models into higher-level, multi-paradigm, distributed simulation, with minimal recoding efforts of existing models.
Abstract: Integrating modelling tools allow different modelling paradigms to coexist and cooperate in the same simulation model. The need for such tools in ecological modelling is due to the high level of complexity of ecological and environmental decision-making problems, their multiple scales of description, the diversity of the available approaches, and the size and heterogeneity of the available datasets. This article discusses problems and perspectives in developing integrating modelling tools and introduces the Simulation Network Interface (SNI), a software package for easy coordination of different existing simulation models. The interface allows the coordination of independent simulation models residing on different machines into higher-level, multi-paradigm, distributed simulation, with minimal recoding efforts of existing models. The interface can also be used to easily provide a remote interface to simulation or data retrieval services running on different architectures. As examples of its application, we describe three ongoing projects using the SNI: (1) the integration of Swarm, an agent-based simulation toolkit, with the Spatial Modelling Environment (SME), a process-based spatial simulation toolkit; (2) the straightforward implementation of a GIS-based spatial data repository for network-based data retrieval and manipulation; and (3) a network-based calibration service for complex simulation models.
65 citations
TL;DR: The package contains several optional programs: a simple trajectory model, as well as models for large-scale spills that encompass a significant area of the water body and for smaller spills that remain localized in an arbitrarily small sub-region.
Abstract: A software package is described for the prediction of the movement and fate of oil spills in the Arabian Gulf. The package is designed to run on a PC operating under Windows and has user-friendly graphical interfaces for model input and for examination of the output. The package contains several optional programs: a simple trajectory model, as well as models for large-scale spills that encompass a significant area of the water body and for smaller spills that remain localized in an arbitrarily small sub-region. The models are based on a three-dimensional hydrodynamical model of the Arabian Gulf that has been tested and calibrated to a high degree of accuracy. The fate of the oil encompasses the processes of evaporation, emulsification, dispersion by wave action into the water column, beaching on the coasts (and possible re-entry into the water body) and mechanical spreading. Examples are shown to illustrate typical input and output screens and to demonstrate the accuracy of the model.
TL;DR: The data matrix model was used to explore the efficiency with which Principal Components Analysis (PCA), without and with Varimax rotation, could derive the imposed gradients, and the dependence of PCA on outliers was decreased by log-transformation of data.
Abstract: An artificial data matrix of element concentrations at sampling locations was created which included six simulated gradients of correlated variables (Ca+Mg, Ni+V, Pb+Cu+Zn, Cd, Fe and K), representing a simplified model of a National survey. The data matrix model was used to explore the efficiency with which Principal Components Analysis (PCA), without and with Varimax rotation, could derive the imposed gradients. The dependence of PCA on outliers was decreased by log-transformation of data. The Components derived from non-rotated PCA were confounded by bipolar clusters and oblique gradients, both resulting in superimposition of two independent gradients on one Component. Therefore, erroneous interpretation of results could result from assessment of variable loadings on Components, without assessment of coupled independent gradients. Varimax rotation greatly improved the results, by rotation of too few Components led to the same problems, and rotation of too many Components led to fragmentation of correlated variables onto single-element Components. The best configuration matching the original model could be selected after investigation of element concentrations superimposed on sample ordinations.
TL;DR: The integrated system developed in the study allows the integration of a comprehensive hydrologic–crop management model (EPIC) with a desktop GIS to function as a planning tool aimed at implementing sustainable farm management practices.
Abstract: Few agricultural producers utilize the true analytical power of GIS and computer simulation models, partly because the loose linkages developed to-date between GIS and most public-domain modeling software are extremely cumbersome to use. The integrated system (EPIC–View) developed in the study allows the integration of a comprehensive hydrologic–crop management model (EPIC) with a desktop GIS to function as a planning tool aimed at implementing sustainable farm management practices. The use of GIS makes possible the integration of diverse spatial data into a comprehensive spatial database. EPIC–View is applied to simulate nitrogen (N) dynamics under conventional and minimum tillage conditions of a field located in Caddo County, Oklahoma. In general, the overall N balance obtained under minimum tillage is better than the balance obtained under conventional tillage over a 5-year model run. Unexplained losses of N averaged 9.55% and 4.2% of the gain in N under conventional and minimum tillage respectively. The integrated modeling system holds immense potential as a farm management tool. Various components of a sustainable agricultural system including irrigation management, crop management, soil management, and pest management, can be efficiently managed. This approach could make farms more economically viable and ecologically sound.
TL;DR: It is found that water leaking out of the North Crimean Canal can result in secondary salinisation of soils and a considerable rise of the watertable within some accumulation zones located downslope, demonstrating that topographically expressed accumulation zones are areas of contact and substance exchange between overland lateral and deep flows.
Abstract: Topographically expressed zones of flow accumulation often coincide with fault intersections because of increased rock fracturing. We have conducted a study of the interrelationships between topographically expressed accumulation zones and fault intersections, and the function of these sites in landscape evolution. The investigation has been performed with the use of digital terrain models, geological and soil data for the Crimean Peninsula. First, we carried out an analysis of associations of sites of fault intersections, intensive rock fracturing and abnormally high discharges of springs and boreholes, relating to fault intersections, with three types of landform element (zones of flow accumulation, transit and dissipation). We found that all phenomena under study are closely associated with topographically expressed accumulation zones. This has demonstrated that, within these zones, the soil moisture is influenced both by upward transport of deep-seated groundwater and by accumulation of overland lateral flows. Second, we predicted the effect of topography on irrigation-induced changes in the salt regime of soils and the groundwater level, assuming that topographically expressed accumulation zones can be marked by properties of fault intersections. We found that water leaking out of the North Crimean Canal can result in secondary salinisation of soils and a considerable rise of the watertable within some accumulation zones located downslope. Salts collected in the accumulation zones, and their slow movement through rock fractures, can lead to salinisation of the aquifers. We believe that topographically expressed accumulation zones are areas of contact and substance exchange between overland lateral and deep flows.
TL;DR: The objective was to explore the possibility of using monthly weather projections in yield estimates, and considered atmospheric CO2 level, total solar radiation, average maximum and minimum temperature, and rainfall for five months of the growing season.
Abstract: Estimation of changes in crop yields is currently based on projections of atmospheric General Circulation Models (GCM) and the use of crop simulators. Crop simulators require daily input of environmental variables. GCMs produce monthly projections of climatic variables. Our objective was to explore the possibility of using monthly weather projections in yield estimates. We considered atmospheric CO2 level, total solar radiation, average maximum and minimum temperature, and rainfall for five months of the growing season. The group method of data handling (GMDH) was applied to relate crop yields to these variables. Projections of GCMs were downscaled to provide daily weather variables for the Mississippi Delta, and weather patterns were obtained in 50 replications for each GCM. The soybean crop simulator GLYCIM was used to generate crop yields on sandy loam, loam and silt loam soils. The equations built with GMDH explained 81‐85% of yield variability, and included solar radiation in July and August, CO2 level, minimum temperature in June and August, and rainfall in August. Published by Elsevier Science Ltd.
TL;DR: The model indicates that the Messara Valley's surface and groundwater resources are very sensitive to climatic variations, with a natural drop in groundwater levels of about 10 m and little surface runoff being possible during drought years.
Abstract: A simple rainfall-runoff model (Vardavas, I.M., 1988. A simple water balance daily rainfall-runoff model with application to the tropical Magela Creek catchment. Ecol. Model 42, 245–264) developed and applied to the tropical wet–dry Magela catchment in the Northern Territory of Australia has been modified and applied to the Mediterranean wet–dry Messara Valley catchment of Crete. The Messara Valley constitutes the most important agricultural region of Crete and is threatened by desertification due to falling groundwater levels. The steep topography of the Messara Valley necessitated the introduction of a two-component sub-surface flow in the rainfall-runoff model, with the slow component representing deep sub-surface flow from the mountains forming the north and south boundaries of the catchment. The original model was also modified to include estimation of the groundwater level fluctuations, and recharge in order to look at possible future exploitation scenarios. While the model was designed for catchments with distinct wet–dry periods, it has been successfully applied to the River Pang catchment in the UK GRAPES (GRAPES, 2000. GRAPES Technical Report, European Commission, ENV4 CT95-0186, 250 pp, March 2000). The model indicates that the Valley's surface and groundwater resources are very sensitive to climatic variations, with a natural drop in groundwater levels of about 10 m and little surface runoff being possible during drought years. The 20 m drop in the groundwater level over the past 10 years is due to the increased irrigation pumping in conjunction with drought years. The model also indicates that the Valley might have gone through cycles of near zero groundwater net recharge every 3–4 years starting in 1982 (an El Nino year).
TL;DR: It is shown that (i) the ozone peak is mostly sensitive to morning solvent releases and traffic emissions, and (ii) that only a few reactions are sensitive although the chemical mechanism used is fairly complete.
Abstract: We present two applications of adjoint modelling with the objective of diagnosing and simulating air pollution in an urban atmosphere. The concerned city is Paris and its surroundings. The first application is the sensitivity of an afternoon ozone peak to anthropogenic emissions and reaction rates. We show in particular the diurnal profile of sensitivity. Despite the paper being mostly methodological, some interesting results come out: we show that (i) the ozone peak is mostly sensitive to morning solvent releases and traffic emissions, and (ii) that only a few reactions are sensitive although the chemical mechanism used is fairly complete. The other application is inverse modelling of the ozone concentrations at the boundaries of the region considered. We demonstrate that the boundary concentrations are in good agreement with independent airborne measurements.
TL;DR: The numerical experiments indicate that the second order implicit–explicit Runge–Kutta methods are a valuable alternative to the conventional operator splitting approach for integrating atmospheric chemistry-transport-models and in cases with stronger accuracy requirements the ‘source splitting’ approach shows a better performance than Strang splitting.
Abstract: Chemistry-transport calculations are highly stiff in terms of time-stepping. Because explicit ODE solvers require numerous short time steps in order to maintain stability, it seems that especially sparse implicit–explicit solvers are suited to improve the numerical efficiency for atmospheric chemistry applications. In the new version of our mesoscale chemistry-transport model MUSCAT [Knoth, O., Wolke, R., 1998a. An explicit–implicit numerical approach for atmospheric chemistry–transport modelling. Atmospheric Environment 32, 1785–1797.], implicit–explicit (IMEX) time integration schemes are implemented. Explicit second order Runge–Kutta methods for the integration of the horizontal advection are used. The stiff chemistry and all vertical transport processes (turbulent diffusion, advection, deposition) are integrated in an implicit and coupled manner utilizing the second order BDF method. The horizontal fluxes are treated as ‘artificial’ sources within the implicit integration. A change of the solution values as in conventional operator splitting is thus avoided. The aim of this paper is to investigate the interaction between the explicit Runge–Kutta scheme and the implicit integrator. The numerical behavior is discussed for a 1D test problem and 3D chemistry-transport simulations. The efficiency and accuracy of the algorithm are compared to results obtained using the Strang splitting approach. The numerical experiments indicate that our second order implicit–explicit Runge–Kutta methods are a valuable alternative to the conventional operator splitting approach for integrating atmospheric chemistry-transport-models. In mesoscale applications and in cases with stronger accuracy requirements the ‘source splitting’ approach shows a better performance than Strang splitting.
TL;DR: The results of this inventory show that road traffic is a very significant source of PM10, however, the re- Suspended Particles originating from loose material present on the paved road surface seems to be several times higher than vehicle exhaust gas emission, a key parameter of air quality in Ile de France.
Abstract: Although the particles in ambient air have adverse effects on the health of the population, very few data on the emissions of PM10 (particles with a diameter of less than 10 μm) released into the atmosphere of Ile de France are available. PM10 are of special interest since they are inhalable. An emission inventory of PM10 was carried out for the following major sources: large combustion installations burning fuel oil or coal; cement factories; waste incinerators and road traffic. The area studied is the “region of Ile de France” (i.e. Paris and the surrounding districts). One of the major challenges encountered during the realization of this inventory was showing that long term (i.e. yearly) estimated emissions are representative values of the activity emitting the pollutant (PM10). For this reason, it was necessary to consider also the quantity of TSP (Total Suspended Particles) which was continuously measured in major factory sites of Ile de France. The results of this inventory show that road traffic is a very significant source of PM10. However, the re-suspension of PM10 originating from loose material present on the paved road surface seems to be several times higher than vehicle exhaust gas emission. This is a key parameter of air quality in Ile de France.
TL;DR: The SPASS model structure facilitates comparison of different model approaches, transfer of improvements between models, development of multi-crop models and modification of process modules for new applications.
Abstract: Crop simulation models are now widely used in agronomy. A highly modular structure has been developed for crop growth simulation models based on the essential processes that are common to various plant species. This generic process-oriented modular structure was implemented in the SPASS (Soil-Plant-Atmosphere System Simulation) model using Microsoft Visual C/C++ under Windows. SPASS is composed of six parts: (i) data management, (ii) memory allocation/initialization, (iii) Modules for crop, soil and microclimate processes, (iv) model configuration and simulation, (v) graphic/table display and (vi) model knowledge integration. The model can be easily configured using the Windows interface by choosing various combinations of process modules developed based on different model approaches. Up to 30 graphic and 5 table MDI (Multiple Document Interface) child windows can be opened during or after the simulation run. Each child window can be resized freely on the screen for the convenience of data analysis. The model theory can be easily viewed using the online theory book. The SPASS model structure facilitates comparison of different model approaches, transfer of improvements between models, development of multi-crop models and modification of process modules for new applications.
TL;DR: A new modification of the Universal Soil Loss Equation, the USLE-M, is better suited to predicting event erosion and also provides a mechanism for accounting for the impact of upslope runoff on erosion that is not available with theUSLE.
Abstract: In the Agricultural Non Source Pollution model (AGNPS), grid-cell erosion is predicted for individual rainfall events using the Universal Soil Loss Equation (USLE) even though the USLE is not well suited for this purpose. A new modification of the USLE, the USLE-M, is better suited to predicting event erosion and also provides a mechanism for accounting for the impact of upslope runoff on erosion that is not available with the USLE. A software system that replaces the USLE by the USLE-M in AGNPS is described and its impact illustrated by an example based on a 1-in-10 year event on a 2300 ha catchment near Nundle, New South Wales, Australia.
TL;DR: A decision support system (DSS) is being developed which will enable explicit prediction of the likely response of key features of the riverine environment to proposed flow management scenarios, and will integrate a range of simple models of riverine ecology which are being developed.
Abstract: The Murray-Darling Basin in Australia is severely environmentally degraded due to anthropogenic changes. Problems include elevated river salinity levels, widespread blooms of toxic blue-green algae, decline of native fish and bird populations, and loss of floodplain wetlands. The community and the government are committed to improving the state of the environment in the Basin, both for its intrinsic ecological values, and to ensure the sustainability of production in Australia’s most economically important agricultural region. To facilitate the trade-off process between users of this resource, an environmental flows decision support system (EFDSS) is being developed to allow explicit prediction of the likely response of key features of the riverine environment to proposed flow management scenarios. The EFDSS is being developed using the RAISON shell (Lam et al. 1994), and will integrate a range of simple models of riverine ecology which are being developed. These models will include qualitative and quantitative models representing the response of different aspects of the instream and floodplain ecology dependent upon the river flow regime. The EFDSS will not include a hydrology model, but will use the outputs from the hydrology models currently in use in the Basin as inputs to the ecological models. The EFDSS will provide a range of tools to allow evaluation of scenarios, as well as explanations and supporting information to elucidate the ecological modelling.
TL;DR: This paper describes the use of the PC-based WINGS and MapInfo Professional geographical information systems in the evolution of a risk assessment methodology to assess catchment risk and illustrates how such technology can assist in environmental decision-making to optimise the quality of drinking water supplies and enhance treatment efficiencies.
Abstract: The process of pollution risk assessment requires the assimilation of data that are spatially variable in nature, making geographical information systems (GIS) an ideal tool for such assessments. Over half of Britain's drinking water is obtained from surface water abstractions, many of which are situated in upland areas. In order to optimise the quality of abstracted waters it is important to assess the possible risks of pollution upstream from the point of abstraction. This paper describes the use of the PC-based WINGS™ and MapInfo Professional™ geographical information systems in the evolution of a risk assessment methodology to assess catchment risk. The work illustrates how such technology can assist in environmental decision-making to optimise the quality of drinking water supplies and enhance treatment efficiencies. Examples are given showing how raster and vector-based data can be used within a GIS framework to produce maps indicating areas of potential hazard to water quality, and coupled with existing models to predict and quantify risk frequency and impact. GIS techniques are further utilised in the formulation of a raw water monitoring programme to assist in intake operation and land-use planning in the catchment. The availability of suitable digital data was found to be variable, and some problems encountered in their integration and implementation within the system framework were resolved. Comment is given on the suitability and relative performance of the two software packages in the assessment of catchment risk. The work was carried out on a medium specification desktop PC, and therefore has the potential to be utilised across the intranet of a large utility company.
TL;DR: The construction of the interface for the AGNPS model and its link with the decision support system RAISON is presented, and the model is described, including the input requirements, the development of tools and the procedures created to extract the necessary data from digital elevation model, soil type and landcover vectorized files.
Abstract: This paper is a progress report of an ongoing research project from which the expected final product will be an integral system to model nonpoint source pollution in surface waters. Diffuse pollution models will be included in a decision support system with a unique platform, common interfaces and GIS capabilities. This system will accommodate pre- and postprocessing tools, model control and sensitivity analysis for the parameters in the models. Particularly, the construction of the interface for the AGNPS model and its link with the decision support system RAISON is presented. The model is described, including the input requirements, the development of tools and the procedures created to extract the necessary data from digital elevation model, soil type and landcover vectorized files.
TL;DR: By facilitating automation of HAZOP, EXPERTOP is expected to contribute significantly to the initiatives of the chemical process and other industries in conducting risk assessment and contribute to an improvement in the production efficiency and, more significantly, risk minimisation of the industries.
Abstract: An expert system has been developed for automating HAZOP (HAZard and Operability) studies. The system, EXPERTOP (EXPERT system for conducting HAZOP) is capable of performing HAZOP studies at significantly lesser costs and with better accuracy than conventional HAZOP studies. By facilitating automation of HAZOP, EXPERTOP is expected to contribute significantly to the initiatives of the chemical process and other industries in conducting risk assessment. This, in turn, would contribute to an improvement in the production efficiency and, more significantly, risk minimisation of the industries. The latter aspect has assumed ever-increasing significance because frequency of industrial accidents has been increasing over the years as has the extent of damage caused by such accidents.
TL;DR: The mathematical background and details of the method as well as practical aspects of its application are presented and discussed and several examples using both synthesised and real world data are presented to explore and illustrate the methodology.
Abstract: A technique is proposed for smoothing a broken line fit, with known break points, to observational data. It will be referred to as ‘broken line smoothing’. The smoothness term is defined by means of the angles formed by the consecutive segments of the broken line, and is given an adjustable weight. The roughness of the resulting broken line can then be controlled by appropriately tuning the weight of smoothness term and the number of straight-line segments. The broken line smoothing can be used for data analysis in several applications as an alternative to other methods such as locally weighted regression and smoothing splines. The mathematical background and details of the method as well as practical aspects of its application are presented and discussed. Also, several examples using both synthesised and real world (hydrological and climatological) data are presented to explore and illustrate the methodology.
TL;DR: The hydrologic submodel is modified and a new method for the prediction of WFPS at the monthly scale from daily rainfall information is developed based on the relationship between monthly rainfall and the number of rainfall events, and the relative cumulative frequency distribution of ranked daily rainfall events.
Abstract: Nitrous oxide (N2O) and nitric oxide (NO) are important atmospheric trace gases participating in the regulation of global climate and environment. Predictive models on the emissions of N2O and NO emissions from soil into the atmosphere are required. We modified the CENTURY model (Soil Sci. Soc. Am. J., 51 (1987) 1173) to simulate the emissions of N2O and NO from tropical primary forests in the Atlantic Zone of Costa Rica at a monthly time step. Combined fluxes of N2O and NO were simulated as a function of gross N mineralization and water-filled pore space (WFPS). The coefficients for partitioning N2O from NO were derived from field measurements (Global Biogeochem. Cycles, 8 (1994) 399). The modified CENTURY was calibrated against observations of carbon stocks in various pools of forest ecosystems of the region, and measured WFPS and emission rates of N2O and NO from soil to the atmosphere.
WFPS is an important factor regulating nutrient cycling and emissions of N2O and NO from soils making the accuracy of the WFPS prediction central to the modeling process. To do this, we modified the hydrologic submodel and developed a new method for the prediction of WFPS at the monthly scale from daily rainfall information. The new method is based on: (1) the relationship between monthly rainfall and the number of rainfall events, and (2) the relative cumulative frequency distribution of ranked daily rainfall events. The method is generic and should be applicable to other areas.
Simulated monthly average WFPS was 0.68±0.02 — identical with the field measurement average of 0.68±0.02 from the annual cycle observed by Keller and Reiners (Global Biogeochem. Cycles, 8 (1994) 399). Simulated fluxes of N2O and NO were 52.0±9.4 mg-N m−2 month−1 and 6.5±0.7 mg-N m−2 month−1, respectively, compared with measured averages of 48.2±11.0 mg-N m−2 month−1 and 7.1±1.1 mg-N m−2 month−1. The simulated N2O/NO ratio was 11.2±1.9 compared with the measured value of 10.9±4.7.
WFPS is the dominant determinant of the fraction of gross N mineralization that is emitted from the soil as N2O and NO. If WFPS were not limiting during part of the year, this fraction would be 4.2%. With some periods of lower WFPS, the realized fraction is 2.2%. Because of the strong relationships between N2O and NO emission rates and rainfall and its derivative, WFPS, these moisture variables can be used to scale up nitrogen trace gas fluxes from sites to larger spatial scales.
TL;DR: In the present work an object-oriented approach has been developed for the analysis of point-source pollution control in river basins, implemented in the design and development of an easily extended and flexible software tool, using the object- oriented language Smalltalk Express.
Abstract: Computer-aided management of surface-water quality has been a field of continuous progress in the last decades. Object-orientation offers the potential for the development of efficient software tools, capable of dealing with the complexity of water resources and their policy making. In the present work an object-oriented approach has been developed for the analysis of point-source pollution control in river basins. The physical entities of the river basin and the conceptual entities of its water-quality simulation and control have been represented through objects. With the appropriate distribution of responsibilities among these objects and the specification of their collaborations, the assessment and simulation of river water quality can be performed. Alternative strategies of point-source pollution control can be also evaluated, and an optimised control scheme can be suggested. The above analysis has been implemented in the design and development of an easily extended and flexible software tool, using the object-oriented language Smalltalk Express. The tool has been successfully validated through the studies of the South Nation River Catchment in Canada and the Upper Mersey River Catchment in the United Kingdom. In this work the architecture of the software tool is outlined and the employed mathematical analysis along with the results of the case studies are presented.
TL;DR: A geographical information system (GIS) based approach for allocating county-level emission estimates to subcounty units and incorporates statistical models to predict the spatial distribution of emission source activities based on widely available data is developed.
Abstract: Current area source emission inventories estimate total emissions for various industrial, commercial, and consumer activities at the county or higher levels. The lack of emission estimates at subcounty levels severely limits the modeling and planning capabilities in urban and regional air quality management. This paper extends current area source emission inventory methodology by developing a geographical information system (GIS) based approach for allocating county-level emission estimates to subcounty units. The new methodology uses GIS to develop and integrate spatial data, to analyze spatial variations in emissions, and to derive input to cell-based air pollution models. This approach incorporates statistical models to predict the spatial distribution of emission source activities based on widely available data. The paper presents an application of the proposed approach to emission inventory of the adhesives and sealants category in the Sacramento modeling region, California.
TL;DR: A general solution for stochastic rumour models is set out, illustrated by an example starting with 1 spreader and 2 ignorants; in this case, the probabilities of 2, 1 and 0 surviving ignorants are 0, 1/4 and 3/4 respectively.
Abstract: The general solution for stochastic rumour models has recently been derived by Pearce (Math. Comput. Modelling. (2000)) for both the Daley–Kendall and Maki–Thompson cases. This paper concentrates on the simpler Maki–Thompson model, which presents some particular problems of its own. A general solution is set out, and illustrated by an example starting with 1 spreader and 2 ignorants; in this case, the probabilities of 2, 1 and 0 surviving ignorants are 0, 1/4 and 3/4 respectively.