Development of a user-friendly software for ecological investigations on river systems, integration of a fuzzy rule-based approach

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1 EnviroInfo 2001: Sustainability in the Information Society Development of a user-friendly software for ecological investigations on river systems, integration of a fuzzy rule-based approach Matthias Schneider 1, Klaus Jorde 2, Frank Zöllner 3 and Franz Kerle 4 Abstract The simulation model CASIMIR for habitat investigations on surface waters is presented. The model is used for the assessment of ecological integrity of rivers by providing quantitative information of habitat qualities for fish, benthic invertebrates and macrophytes. Different scenarios concerning flow rates and regimes as well as structural modifications can be simulated to find optimum management strategies. Within the modelling procedure a fuzzy-rule based approach gives the opportunity to integrate linguistic expressions and expert knowledge about fish behaviour and habitat demands. Examples of the model application to minimum flow regulation and river restoration are given. 1. Introduction The majority of the rivers and brooks in the whole world, particularly in areas with high population density was strongly influenced by men for centuries. Due to quite differing usage requirements most running waters systems cannot fulfil their original, important functions in the ecological complex any more This negatively affects animals as well as plants. In many cases these effects are the reason for counter measures only if they concern man directly. Examples are the reduced water quality, changed flood events or reduced fishery yields. In the last decades the significance of rivers as particularly species-rich ecological systems was realized and found entrance in guidelines and legal texts. Recent example is the water framework directive of the European union (Rat der Europäischen Union, 2000), in which "good quality" of the surface waters is required within the next years. However for handling the usually very complex questions of water man- 1 Dr.-Ing. Matthias Schneider, sje Schneider & Jorde Ecological Engineering GmbH, Viereichenweg 12, D Stuttgart, Germany mailbox@sjeweb.de, 2 Prof. Dr.-Ing. Klaus Jorde, College of Engineering, University of Idaho, Boise, USA 3 Dipl.-Ing. Frank Zöllner, Institut für Wasserbau, Universität Stuttgart, Stuttgart, Germany 4 Dipl.-Ing. Franz Kerle, Institut für Wasserbau, Universität Stuttgart, Stuttgart, Germany

2 355 agement suitable instruments are still missing, since usually little is known about the interactions within ecological systems or can only be described in a qualitative way. 2. Habitat Modelling One of the most important instruments for the analysis of river ecology are habitat models. They can predict the quality of the habitats for organisms living in the regarded system. The special advantages of this approach are explained by the following facts: 1. The ecological quality of a river system is directly coupled with the living conditions of the typically resident organisms. 2. Habitat models can predict the influence of discharge and structural changes on fish, invertebrates and macrophytes. 3. Instream flow changes affect primarily water depths, flow velocities and substrate composition, which all are main factors for habitat quality. 4. By relating habitat quality to discharge or river modifications a quantitative base is given for the comparison and evaluation of ecological values and the requirements for use. Due to these advantages habitat modelling is a common approach for river management in North America. Usually physical habitat is simulated, by regarding relations between hydraulic or structural parameters (e.g. flow velocity, bottom structure) and the requirements of the water organisms (e.g. BOVEE et al., 1998). So far mainly fish, especially the economically interesting salmonides, were regarded. At the institute of hydraulic engineering of the University of Stuttgart the simulation model CASIMIR (Computer Aided SImulation Model for Instream flow Requirements) has been developed since the beginning of the 90's. In contrast to the North American models CASIMIR first concentrated on habitats for benthic organisms bound to the river bottom (JORDE, 1996). The original motivation was the question of the minimum flow in river sections affected by hydro power plants of the diversion type, a very common type in some European countries. Therefore possibilities for economy investigations were integrated. In the meantime the modular structured model system has been extended by the highly resolved river model SORAS (Structure Oriented River Analysing System), that enables the analysis of the aquatic and riparian zones as habitats for fish and vegetation. The range of application has been extended and habitat models can be used in the following fields: 1. Flow regulations, 2. Structural quality, effects of river regulation, 3. River restoration, 4. Watershed management.

3 Modelling procedure and new approach The classical way for the linkage of physical and biological parameters in habitat modelling are so-called preference functions. These functions indicate by a suitability index SI between 0 (unsuitable) and 1 (optimum Suitability) the fulfilment of habitat requirements concerning a physical parameter i.e. water depth. They are mostly univariate and in the modelling process total suitability is calculated using different combination methods. The result can vary a lot depending on the selected method and interaction of parameters usually cannot be considered In CASIMIR a calculation procedure based on fuzzy logical principles was implemented (SCHNEIDER, 2001). This method has got several advantages compared with other multivariate procedures: 1. Knowledge about the habitat demands of waters organisms is usually qualitative, by the fuzzy rule-based approach this knowledge can be numerically processed. 2. Fuzzy logical calculations consider multivariate effects but no independence of the input parameters is required. 3. A comparatively small number of measured or observed values is needed. 4. New parameters can be included easily. 5. The calculation steps can be easily understood (no black box effect) and interactions within the system can be explained. Basic component of the approach are membership functions called fuzzy sets (BARDOSSY & DUCKSTEIN, 1995), by which linguistic variables can be defined, i.e. high, medium or small flow velocity (Figure 1). This kind of definition is very suitable for the formulation of ecological problems, since they rarely can be described by exact functions or crisp numbers. Thus available expert knowledge can be integrated effectively in the calculations using inference rules. These rules define the suitability of a certain combination of input parameters for a life stage of a fish species (KAPPUS et al., 2000). An example for such a rule is given by the following expression: 1 membership [-] small medium high v [m/s] Figure 1: Fuzzy Sets describing the input parameter flow velocity

4 357 IF water depth is small AND flow velocity is high AND substrate size is medium THEN habitat suitability is high. It is evident that this kind of rules is very close to the human way of communication and a convenient way to integrate expert knowledge. Additionally, using this approach the adjustment of the model to different river types is possible, since the physical parameters may be on different levels in different river types but the preferences of an organism within the system can be very similar. Experiences in fish habitat modelling showed that the fuzzy-rules necessary for the numeric processing were formulated very similar by different experts. This seems to confirm the proximity of the approach to human thinking. 4. Applications In the last years CASIMIR was tested and extended in various scientific and application-oriented projects and has proven its suitability in river types of different altitude, hydraulics, structure and dimension i.e.: 1. Flow regulations and investigations of environmental integrity for hydroelectric power plants of different dimensions. 2. Investigations of river sections influenced by hydropeaking. 3. Contribution for the development of a standardized procedure for certifying hydroelectric power plants (assignment of Swiss "Oekostrom" label). 4. Management strategies for river sections influenced by water diversion. 5. Economical investigations concerning the reactivation of hydroelectric power plants. 6. Assessment and evaluation of ecological effects caused by river regulations. 7. Contribution to the development of a model system for the integrated watershed management (MIMAG). For the assessment of a minimum flow regulation in the context with the reactivation of a hydro power plant in western Germany the development of habitat availability for different benthic and fish species was one of the main factors. As an example for the model output the suitability for graylings during the spawning period can be visualized in maps (Figure 2) indicating suitability classes between 0 (unsuitable) and 1 (optimum suitability). By calculating these suitabilities for different discharges and integrating them to a single value (WUA = weighted usable area) a function of habitat availability over discharge can be generated (Figure 3). If this is done for selected indicator species and their life stages, a flow regulation with minimized ecological impacts, adapted to the demands of the river fauna can be found.

5 358 grayling - spawning 1890 l/s 200 m 5000 l/s Habitat suitability poor good Figure 2 Map of habitat suitabilities for spawning grayling generated by CASIMIR WUA / wetted area 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% spawning juvenile fry Q [l/s] Figure 3 Function of habitat availability over discharge for different life stages of grayling Another important feature integrated in the CASIMIR-module SORAS is the modification of channel geometry and morphology. It gives the opportunity to estimate the effects of changed flow conditions and bottom structures on physical habitat quality. In many cases measures improving the morphologic properties of a river are more efficient than just flow regulations. CASIMIR provides user-friendly features to alter cross-section geometries or substrate types (Figure 4) and in this manner is a tool to evaluate different scenarios of river modifications and flow regimes.

6 359 Figure 4 Example of CASIMIR user-interface cross-section, showing flow-velocity and substrate types 5. Conclusions and Outlook CASIMIR so far is the only existing tool for the ecological investigation of rivers considering habitats for fish, benthic invertebrates and macrophytes at the same time. The additional options of channel modification in combination with discharge time series make it a very useful instrument for the evaluation of different scenarios including restoration measurements and flow regulations. An extension for the investigation of floodplains and larger scales using information derived from standardized methods for structural quality analysis is being developed.

7 360 Bibliography Bardossy, A. & Duckstein, L. (1995): Fuzzy Rule-Based Modelling with Applications to Geophysical, Biological and Engineering Systems.- CRC Press, Boca Raton, New York, London, Tokio. Bovee, K.D.; Lamb, B.L.; Bartholow, J.M., Stalnaker, C.B.; Taylor, J.; Henriksen, J. (1998): Stream Habitat Analysis using the Instream Flow Incremental Methodology. - Information and Technology Report USGS/BRD/ITR , US Department of the Interior, US Geological Survey Biological Resources Division. Jorde, K. (1996): Ökologisch begründete, dynamische Mindestwasserregelungen bei Ausleitungskraftwerken. Dissertation, Mitteilungen des Instituts für Wasserbau, Universität Stuttgart, Heft 90, Eigenverlag, Institut für Wasserbau der Universität Stuttgart, Stuttgart. Kappus, B.; Siligato, S.; Böhmer, J.; Jansen, W.; Schmid, H. (2000): Ermittlung von Fischhabitatpräferenzen als Grundlage einer hydraulisch-morphologischen Simulation zur Habitatprognose in Fließgewässern. - Abschlussbericht im Auftrag des Instituts für Wasserbau der Universität Stuttgart, Prof. Dr. H. Rahmann, Institut für Zoologie, U- niversität Hohenheim. Rat der Europäischen Union (2000): Richtlinie 2000/60/EG vom 23. Oktober 2000 zur Schaffung eines Ordnungsrahmens für Maßnahmen der Gemeinschaft im Bereich der Wasserpolitik. - Luxemburg. Schneider, M. (2001): Habitat- und Abflussmodellierung für Fließgewässer mit unscharfen Berechnungsansätzen. Dissertation, Mitteilungen des Instituts für Wasserbau, Universität Stuttgart, Eigenverlag, Institut für Wasserbau der Universität Stuttgart, Stuttgart, in Vorbereitung.