Browsing by Author "Cattrysse, Dirk"

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A linear programming approach to optimise the management of water in dammed river systems for meeting demands and preventing floods
(2018) Veintimilla Reyes, Jaime Eduardo; De meyer, Annelies; Cattrysse, Dirk; Van Orshoven, Jos
Water in sufficient quantity and quality is indispensable for multiple purposes like domestic and industrial use, irrigated agriculture, hydropower generation and ecosystem functioning. In many regions of the world, water availability is limited and even declining. Moreover, water availability is variable in space and time and often does not match with the spatio- temporal demand pattern. To overcome the temporal discrepancy between availability and consumption, reservoirs are constructed. Monitoring and predicting the water available in the reservoirs, the needs of the consumers and the losses throughout the river and water distribution system are necessary requirements to fairly allocate the available water to the different users, prevent floods and ensure sufficient water flow in the river. In this paper, this surface water allocation problem is considered a Network Flow Optimisation Problem …
A multiple criteria heuristic solution method for locating near to optimal contiguous and compact sites in raster maps
(2011) Vanegas, Pablo; Cattrysse, Dirk; Van Orshoven, Jos
A high performance heuristic solution method is proposed able to locate near to optimal sites composed by a given number of cells (raster structure). These sites must be compact and maximize levels of the sites intrinsic multiple criteria suitability. To validate the heuristic approach, a comparison with a mathematical formulation is performed with afforestation data of regions within the Netherlands, Denmark, and Flanders. This reveals that the heuristic is considerably faster than the mathematical method and the objective values obtained with the two approaches are substantially similar. A sensitivity analysis shows that the region's homogeneity plays an important role in the performance of the process identifying most favourable sites. Moreover, computation time follows a power model in the number of cells forming the site.
An NFO-LP-model to optimise water allocation in dammed river systems
(Universiteit Gent, 2017) Veintimilla Reyes, Jaime Eduardo; Cattrysse, Dirk; Van Orshoven, Jos; Veintimilla Reyes, Jaime Eduardo
Water of sufficient quantity and quality is indispensable for domestic and industrial use, irrigated agriculture, hydropower generation and ecosystem functioning. River systems are a major source of water to meet these demands. Excess surface water resulting into floods is harmful though for properties and infrastructures and may put human lives at risk. Since surface water availability is variable in space (eg related to latitude and orography) and time (seasonal) it often does not meet the spatio-temporal use requirements. To overcome this discrepancy reservoirs have been or are planned to be constructed on many large and smaller river systems throughout the globe. Management of these reservoirs with a view to allocate the available water fairly and to prevent floods requires time series data on inflow, demands and losses. In this contribution, this water allocation problem is considered as a …
Budget constraint in reforestation meant for minimizing sediment load at a watershed outlet
(2010-03-17) Vanegas, Pablo; Cattrysse, Dirk; Van Orshoven, Jos
Policy and decision makers dealing with environmental conservation and land use planning often require identifying potential sites for contributing to minimize sediment flow reaching riverbeds. This could be one of the environmental objectives of reforestation initiatives. An Integer Programming (IP) formulation for selecting a predefined number of locations to minimize sediment load at a watershed outlet has been previously developed in [1]. This paper tests that formulation under the assumption that the area to be reforested is not known in advance, a budget constraint is included instead. Therefore the extension of the reforested area is subject to this budget constraint, which makes the problem more complex. Several experiments are performed for two watersheds in South Dakota in the USA. The results show the sediment load at the watershed outlet as well as the erosion levels, slopes and distances to the riverbeds of the locations selected to be reforested.
Compactness and flow minimization requirements in reforestation initiatives: An integer programming (IP) formulation
(2009) Vanegas, Pablo; Cattrysse, Dirk; Van Orshoven, Jos
Identifying optimal sites on raster maps is a complex problem when the sites are larger than the cell size. Optimal sites involves a trade-off between the intrinsic characteristics of individual cells and the spatial configuration of the cells. Although there are a number of techniques to solve the site allocation problem, those solutions do not consider spatial interactions between the cells forming the site. This paper presents an Integer Programming Formulation (IP) for allocating a predefined number of cells satisfying the following criteria: 1) minimize flow (water, sediment) reaching the outlet of a watershed, 2) maximize/minimize intrinsic characteristics of the cells, and 3) form a compact patch. Although the core structure of the IP formulation can be applied for different sorts of flow and intrinsic characteristics, it is targeted to a reforestation application. The proposed approach is applied to perform several experiments in two watersheds in South Dakota in the USA for searching a given number of best cells (1) minimizing sediment reaching the watershed outlet,(2) maximizing the environmental criteria, and (3) forming a compact patch. The results obtained with the IP formulation are in agreement with expert assessments of erosion levels, slopes and distances to the riverbeds.
Compactness in spatial decision support: A literature review
(2010-03-23) Vanegas, Pablo; Cattrysse, Dirk; Van Orshoven, Jos
The development of Spatial Decision Support Systems (SDSSs) which explicitly consider spatial relations has had a significant growth over recent years. The main intention of this paper is reviewing spatial optimization approaches for identifying contiguous and compact areas fulfilling particular criteria. These approaches explicitly consider topological spatial relations between geographical entities (cells, lines, points, areas). In this direction, spatial optimization techniques as heuristics, meta-heuristics, and mathematical programming are reviewed. Since the application fields, the nature of the approaches, the data format, and the size of the reviewed works are very diverse, high level comparison is made in order to identify critical issues regarding the identification of contiguous and compact areas in digital geographical information.
Diseño e implementación de un sistema de soporte de decisiones para el Centro de Documentación Regional “Juan Bautista Vázquez”
(Universidad de Cuenca, 2014) Haro Valle, Valeria Alexandra; Pérez Rocano, Wilson Rodrigo; Sigüenza Guzmán, Lorena Catalina; Cattrysse, Dirk; Saquicela Galarza, Víctor Hugo; Universidad de Cuenca; Dirección de Investigación de la Universidad de Cuenca; DIUC
In recent years, volume of library-related data has increased tremendously, as well as complexity of data sources and formats have been escalating. This information explosion has created a big challenge for data managing, archiving and accessing, especially in support of library decision-making. Knowing that a good library management involves integrating a number of strategic indicators, the implementation of a Data Warehouse (DW), that properly manages such amount of information and the complex mix of data sources, becomes an interesting alternative to be considered. This article describes the design and implementation of a decision support system based on a DW approach for the Regional Documentation Centre “Juan Bautista Vazquez”. To assure that all relevant data sources are included during the data analysis, the study utilizes a holistic methodology, previously proposed by Siguenza-Guzman et al. (2014) for an integrated library evaluation. This methodology assesses the library collection and services by incorporating important elements for library management, such as service performance analysis, service quality control, collection usage analysis, and information retrieval quality. Based on this data analysis, the study proposes a DW architecture to integrate, process and store the relevant data. These stored data are finally analyzed and visualized by the so-called online analytical processing (OLAP) tools. Initial tests of the implemented decision support system confirm the feasibility and effectiveness of the DW based approach, by successfully integrating multiple and heterogeneous sources, formats and varieties of information, permitting library managers to generate personalized reports, and even allowing to debug the day-to-day transactional processes.
Finding sites meeting compactness and on- and off-site suitability criteria in raster maps
(2010-02-16) Vanegas, Paul; Wijffels, Anja; Cattrysse, Dirk
This paper presents an evaluation of the Heuristic for Locating Cells (HLC) for identifying optimal sites in raster maps. The optimal sites are the result of a trade-off between the on-site suitability of individual cells, their spatial configuration, and their off-site impact at the watershed outlet. The evaluation is targeted to a case of reforestation in two sub-basins within the Tabacay catchment in the southern Andes of Ecuador. The case is set up to locate a predefined number of cells 1) forming a compact patch, 2) minimizing sediment reaching the watersheds outlet, and 3) maximizing cell-specific performance, i.c. carbon sequestration and monetary income as a result of reforestation with pine trees. The evaluation confirms that the heuristic is capable of identifying high quality compact patches of cells with maximal on-site performance while minimizing sediment delivery.
GI-technology: Adaptive generator of spatio-temporal decision support systems for land use planning
(2010) Wijffels, Anja; Van Orshoven, Jos; Muys, Bart; Cattrysse, Dirk
To deal with the complexity of land use allocation in a spatio-temporally variable context, a generic framework for automated support to multi-objective land use planning is proposed. The framework is rooted in the discipline of land evaluation which is considered a go-between between land resources survey and land use planning. It draws on own experiences and on lessons learnt from literature. It consists of five integrated and interoperable components. The core three ones, the spatio-temporal database, the engine for data query, transformation and analysis and the user interface are adopted from geographical information systems (GIS). A ‘knowledge and model base’ component adds capability for assessing land performance over time. Finally, a multicriteria decision analysis component allows for identifying optimal land units and optimal land use options. The framework’s applicability and the limitations of geographical information technology (GI-Technology) to generate spatio-temporal decision support systems (stDSS) are illustrated with two cases: one in data rich and one in data poor conditions.
Integer Programming (IP) formulation for minimizing sediment delivery in a watershed by reforestation of optimal sites
(2009-08-12) Vanegas, Pablo; Cattrysse, Dirk; Van Orshoven, Jos
Several approaches exist to model the production, transport and delivery of water and sediment flows in watersheds but none of these are dealing with spatial optimality requirements. However, policy and decision makers dealing with environmental conservation and land use planning often require identifying potential sites for contributing to minimize sediment flow reaching riverbeds. This is the case of reforestation initiatives, which can have sediment flow minimization among their objectives. This paper proposes an Integer Programming (IP) formulation for selecting a predefined number of locations to minimize sediment load at a watershed outlet. Although the core structure of the IP model can be applied for different sorts of flow, the formulation is targeted to minimization of sediment delivery. Several experiments are performed for two watersheds in South Dakota in the USA. The results are in agreement with expert assessments of erosion levels, slopes and distances to the riverbeds, which in turn allows concluding that this approach is suitable for minimizing sediment flow.
Localización de sitios en mapas raster para minimizar impactos de flujo
(Universidad de Cuenca, 2010-12) Vanegas, Pablo; Cattrysse, Dirk; Van Orshoven, Jos; Universidad de Cuenca; Dirección de Investigación de la Universidad de Cuenca; DIUC
Policy and decision makers dealing with environmental conservation and land use planning often require identifying potential sites for contributing to minimize sediment flow reaching riverbeds. This is the case of reforestation initiatives, which can have sediment flow minimization among their objectives. This paper proposes an Integer Programming (IP) formulation and a Heuristic solution method for selecting a predefined number of locations to be reforested in order to minimize sediment load at a given outlet in a watershed. Although the core structure of both methods can be applied for different sorts of flow, the formulations are targeted to minimization of sediment delivery. The proposed approaches make use of a Single Flow Direction (SFD) raster map covering the watershed in order to construct a tree structure so that the outlet cell corresponds to the root node in the tree. The results obtained with both approaches are in agreement with expert assessments of erosion levels, slopes and distances to the riverbeds, which in turn allow concluding that the studied approaches are suitable for minimizing sediment flow.
Mathematical programming for the support of river water management: water allocation and reservoir location
(Katholieke Universiteit Leuven, 2022-05-20) Veintimilla Reyes, Jaime Eduardo; Van Orshoven, Jos; Cattrysse, Dirk; Vanegas Peralta, Pablo Fernando; Cisneros Espinoza, Felipe Eduardo
Surface and ground water availability is variable in space and time and the spatio-temporal pattern of this variability often does not match with the distributed use pattern of sectors and individual consumers. This mismatch can become controversial when overall water availability decreases, e.g., due to climate change, and competition for water increases. It is in this context that the so called WEF-nexus between water for human consumption and industrial use, water for Energy (hydropower) and water for Food (irrigated agriculture) (WEF) has gained increasing attention in research, business and policy spheres, especially in regions with more arid climate. An additional dimension of this nexus is the water required for sustainable functioning of ecosystems in general and wetlands in particular. Allocation of scarce water has challenged water managers for decades. The construction and operation of reservoirs is the typical solution put forward. In this research we addressed the optimization of the allocation of water available in a river-with-reservoir system towards multiple users as a network flow optimization (NFO) problem. There are two classes of methods to tackle NFO problems: heuristic models and mathematical models. Heuristic models are able to provide a feasible solution within reasonable computation time whereas mathematical models are able to come up with the optimal solution but often requiring longer computation times. Since for strategic decisions computation times are less crucial, the latter, i.e. linear programming (LP) models and mixed integer linear programming (MILP) models were the subject of this research. LP and MILP models were formulated to optimize the flow and storage of water through Water Supply Networks (WSN) created from geographic information describing the river basin under study. A WSN encompasses a set of oriented lines connected in georeferenced nodes whereby the lines represent river segments and the nodes represent reservoirs, natural water bodies, inflow points and abstraction points. Whereas inflow and abstraction points are characterized by time series of incoming and required water volumes, the water volume available in river segments, reservoirs and other water bodies, each having predetermined capacities, is updated throughout the simulation period.
Optimal resource allocation and budgeting in libraries
(2015-08-01) Sigüenza Guzmán, Lorena Catalina; Cattrysse, Dirk; Verhaaren, Henri
A spatially explicit approach to the site location problem in raster maps with application to afforestation (Een ruimtelijk expliciete aanpak voor het locatieprobleem in rasterkaarten met toepassing op bebossing)
(Katholieke Universiteit Leuven, 2010-09-02) Vanegas Peralta, Pablo Fernando; Cattrysse, Dirk; De Schreye, Daniel
Environmental conservation and land use planning usually need to automatically identify geographical sites satisfying particular criteria. The identification of sites becomes more complex when spatial configurations of the sites are part of the requirements since topological relations need to be considered in the analysis of digital geographical data. The present research develops heuristic methods and mathematical approaches to automatically identify contiguous and compact sites to be afforested. In addition to spatial configurations, other criteria related to the identification of sites are part of this research: maximization of environmental performance, sediment fow reduction by means of afforestation of compact sites and budget restrictions in afforestation. One of the results of the AFFOREST project (EU 5th Framework Programme for Research and Technological Development) was a Decision Support System (DSS) that is capable to identify high quality sites to be afforested (transformation of agricultural land into forest). Those sites maximize the Environmental Performance (EP) in terms of three Environmental Impact Categories (EIC): carbon sequestration to be maximized, nitrate leaching to be minimized and ground water recharge to be maximized. To this end every EIC is represented by means of a map composed by a grid of cells (raster map), hence the objective is to identify a site made up of a subset of cells maximizing the EP. The cells identified by means of the AFFORESTDSS form a fragmented site, nevertheless it is also useful to identify sites that are contiguous and compact. Compactness facilitates to articulate efficient policies to manage the afforested areas, in order t0 achieve not only environmental but also economical benefits. This research develops new approaches to locate compact sites for maximizing EP.
Synergizing industrialized and developing countries to improve resource recovery for e-waste: case study Belgium - Kenya
(2014) Vanegas, Paul; Peeters, Jef R.; Plessers, Frank; Cattrysse, Dirk; Duflou, Joost R.
Due to high labor costs, e-waste recycling companies in industrialized countries increasingly adopt destructive mechanical pre-processing based treatments. These processes perform poorly for precious metals and plastics due to material incompatibility and increased entropy, resulting in low effective recycling efficiencies for these material categories. In developing countries most e-waste treatments consist of manual dismantling, followed by primitive refining techniques, which is not only inefficient, but also poses a serious threat to the environment. This article assesses, from an economic and environmental perspective, a cooperation scenario between Belgium and Kenya in which manual dismantling and state of the art metal refining techniques for recycling computers are combined. Findings show that international cooperation could offer a more sustainable solution, yet measures must be taken to avoid the “cherry picking” of valuable components and environmentally unsound disposal of the remaining parts.
Upgrading geographic information systems to spatial decision support systems
(2011-04-17) Van Orshoven, Jos; Kint, Vincent; Wijffels, Anja; Estrella, René; Bencsik, Gergely; Vanegas, Pablo; Muys, Bart; Cattrysse, Dirk; Dondeyne, Stefaan
A GIS is capable of identifying a set of land units meeting positional, temporal, topological and multiple on-site attribute criteria. Based on the combination of its generic analytical functionalities, a GIS can also be used to rank the alternative land units and propose the best or worst ones in terms of the non-weighted or weighted criteria. More advanced multi-criteria decision methods are however not easily incorporated in the GIS-framework so that extension with dedicated tools is required to upgrade the GIS to a full blown sDSS. In this paper we illustrate this upgrading of GIS to sDSS and we argue that when also temporal alternatives are dealt with, the DSS can be termed spatio-temporal. Three statements are made: (i) the presented rationale is challenged by phenomena of spatial and spatio-temporal interaction, (ii) important research avenues are present in order to optimize topological and off-site decision attributes in the spatial and spatio-temporal decision problems and (iii) the forestry domain is very suitable for study and application of all the mentioned issues due to the explicit spatial and temporal nature of the management issues which must be addressed.