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Auflistung nach Autor:in "Luther, Bernhard"

1 - 8 von 8
  • Konferenzbeitrag
    A Water Quality Simulation Model for a Lowland River-lake System
    (Informatics for Environmental Protection - Networking Environmental Information, 2005) Luther, Bernhard; Gnauck, Albrecht; Meisch-Peschew, Alexander
    Polluted water affects not only the functioning of freshwater ecosystems and various water uses, but risks human health. One of the long-term environmental problems of freshwater ecosystem management is the control of eutrophication. It is characterised by an intensive increase of dissolved nutrients in water bodies, by excessive growth of plants, mainly algae, and by restricted water uses due to anoxic water conditions as well as by odour problems. It refers to intensive man-made activities in the river catchment. The simulation framework presented consists of a combination of the MATLAB based simulation models SpreeMod and HavelMod. The simulator SpreeMod describes water quality changes along a river stretch while the simulator HavelMod covers water quality changes in shallow riverine lakes. Both simulators are coupled by interfaces which switch the model type from river to lake and vice versa. This simulation framework covers not only a long distance but also different types of freshwater ecosystems with changing dynamic water quality behaviour. Model state variables are phytoplankton, zooplankton, orthophosphate phosphorus, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, dissolved oxygen and biological oxygen demand. External driving forces are photoperiod, solar radiation and water temperature. For simulation input sampled raw data are treated by interpolation methods to generate equidistant data. In this paper simulation results of the lowland river-lake system formed by the rivers Spree and Havel close to the Berlin/Potsdam region are discussed.
  • Konferenzbeitrag
    Coupling of Simulators for Optimal Control of Water Quality
    (The Information Society and Enlargement of the European Union, 2003) Gnauck, Albrecht; Luther, Bernhard; Wiedemann, Thomas; Krug, Wilfried
    The control of water quality of freshwater ecosystems is inherently multiobjective. Mostly, scenario analyses based on simulation runs of one or more models are carried out. Some applications are known where a two stage simulation-optimisation combination help to solve water quality management problems. To control the water quality of shallow lakes the MATLAB based simulator HavelMod was coupled with the optimisation simulator ISSOP. In the paper the coupling procedure is described and the effects referring to two control strategies of water quality are discussed.
  • Konferenzbeitrag
    Data Filtering and Simulation of Water Quality of Shallow Lakes
    (Sh@ring – EnviroInfo 2004, 2004) Gnauck, Albrecht; Luther, Bernhard
    Sustainable management decisions to control the quality of freshwater ecosystems can only be achieved by using powerful simulation tools where the functioning of ecosystems and water uses will be affected by polluted water. One of the long-term environmental problems of freshwater ecosystem management is the control of eutrophication. Usually water quality time series contain missing data or irregular sampled data. In such cases data have to be added to get records based on a regular time grid. Based on filtered data results of a water quality simulation and optimisation framework for shallow lakes are presented. This framework consists of a simulation model (HavelMod) coupled with an optimisation procedure (ISSOP). To get management decisions two control strategies are discussed.
  • Konferenzbeitrag
    Decision Theory Based Monitoring Design for Freshwater Ecosystems
    (Environmental Informatics and Industrial Ecology, 2008) Luther, Bernhard; Gnauck, Albrecht
    An environmental monitoring design in general and a freshwater monitoring system in special focus on important variables of an ecosystem which give a decision maker the possibility to select different types of actions from the domain of decision. In this sense, a decision model is divided into the part of the decision maker and its environment. The preferences of the decision maker are modelled by preference structures. They cover outranking methods as well as methods of multi-attribute utility theory. Additionally, the decision maker’s indifferences have to be gained by setting up threshold values or more advanced methods like automatic classification and fuzzy logic. In this paper the water quality status of the Spree-Havel waterway is compared using different methods based on decision theory in order to find out sampling points with the highest level of environmental information. It can be stated that the suitability of these methods depend on the desired information content. On the one hand, a set of sampling points can be well-arranged in transitive relations like rankings or Hasse diagrams. On the other hand, pair wise comparisons may be helpful which are obtained by ELECTRE I.
  • Konferenzbeitrag
    Missing Data in Environmental Time Series - a Problem Analysis
    (Informatics for Environmental Protection - Networking Environmental Information, 2005) Gnauck, Albrecht; Luther, Bernhard
    Missing data in environmental time series lead to some general problems in many fields of environmental research and simulation. They cause not only difficulties in process identification and parameter estimation but also misinterpretations of spatial and temporal variations of environmental indicators. Mostly, time series represent samples of data at discrete time events based on various sampling intervals. For modelling and simulation of environmental processes time series must be mapped on a regular time grid. This procedure is known as re-sampling of time series and consists on data interpolation or, in the case of disturbed signals, on data estimation. Some well-known linear and nonlinear interpolation methods exist while data estimation can be done by static and dynamic approximation procedures. Regression type functions or in the case of cycling time series Fourier approximation are used. In opposite of that, digital filtering procedures deliver consistent equidistant data estimates based on major signal frequencies. In the paper different algorithms of data interpolation and approximation are applied on irregularly sampled water quality time of rivers with different hydraulic conditions. Additionally, low pass filters are checked to find out the best filter function for each environmental indicator.
  • Konferenzbeitrag
    Modelling and Simulation of Internal Pollution of Shallow Lakes
    (Environmental Communication in the Information Society - Proceedings of the 16th Conference, 2002) Gnauck, Albrecht; Luther, Bernhard; Heinrich, Ralph
    In this paper results of a water quality modelling framework for riverine shallow lakes are presented. Based on investigations of interrelations between variables of freshwater quality by advanced time series analysis methods a process model for phosphorus remobilisation from lake sediments was developed. For predicting the changing water quality of shallow riverine lakes caused by internal pollution this submodel was included into the eutrophication model HavelMod. Simulations of water quality variables for different river-lake sections as phytoplankton biomass, phosphate phosphorus, ammonia nitrogen and nitrate nitrogen, which are important for water quality management activities, are discussed.
  • Konferenzbeitrag
    Simulation of Eutrophicationof Shallow Lakes of the Lower Havel River
    (The Information Society and Enlargement of the European Union, 2003) Gnauck, Albrecht; Heinrich, Ralph; Luther, Bernhard
    In this paper results of an eutrophication modelling framework for shallow lakes are presented. Based on investigations of variables of freshwater quality by advanced time series analysis methods the process of phosphorus remobilisation from lake sediments was modeled and included into an eutrophication model. Simulation results of essential water quality indicators as phytoplankton biomass and phosphate phosphorus are discussed.
  • Konferenzbeitrag
    Water Quality Management of a Sub-Watershed of the River Elbe
    (Environmental Communication in the Information Society - Proceedings of the 16th Conference, 2002) Gnauck, Albrecht; Heinrich, Ralph; Luther, Bernhard
    Applying multi-objective decision making methods to water quality management tasks optimal compromise solutions between ecological and man-made management operations will be obtained. The DSS REHSPROX was used to compute Pareto-optimal solutions of the DO balance of the Upper Spree River as a part of the River Elbe basin. For this reason, contradictory water quality and economical goal functions describing different management policies are taken into consideration. According to multi-objective optimisation results cost functions for investments are presented.