Browsing by Author "Van Orshoven, Jos"

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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.
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.
MILP for optimizing water allocation and reservoir location: a case study for the Machángara river basin, Ecuador
(2019) Veintimilla Reyes, Jaime Eduardo; De Meyer, Annelies; Cattryss, Dirk; Tacuri Espinoza, Víctor Eduardo; Cisneros Espinoza, Felipe Eduardo; Van Orshoven, Jos; Vanegas Peralta, Pablo Fernando
The allocation of water flowing through a river-with-reservoirs system to optimally meet spatially distributed and temporally variable demands can be conceived as a network flow optimization (NFO) problem and addressed by linear programming (LP). In this paper, we present an extension of the strategic NFO-LP model of our previous model to a mixed integer linear programming (MILP) model to simultaneously optimize the allocation of water and the location of one or more new reservoirs; the objective function to minimize only includes two components (floods and water demand), whereas the extended LP-model described in this paper, establishes boundaries for each node (reservoir and river segments) and can be considered closer to the reality. In the MILP model, each node is called a “candidate reservoir” and corresponds to a binary variable (zero or one) within the model with a predefined capacity. The applicability of the MILP model is illustrated for the Machángara river basin in the Ecuadorian Andes. The MILP shows that for this basin the water-energy-food nexus can be mitigated by adding one or more reservoirs.
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.