Tesis Doctoral/PHD

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Browsing Tesis Doctoral/PHD by Author "Cattrysse, Dirk"

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    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.
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    Optimal resource allocation and budgeting in libraries
    (2015-08-01) Sigüenza Guzmán, Lorena Catalina; Cattrysse, Dirk; Verhaaren, Henri
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    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.