Factsheet: System Dynamics Models
Definition
System Dynamics Models (SDM) and System Thinking is a methodology for studying and managing complex feedback systems. It started from the idea of applying concepts from feedback control theory to the study of industrial systems.
The system dynamics approach is typically used where no formal impact assessment (i.e. simulation models) exist, but could be developed by linking a number of feedback mechanisms.
Application objectives
SDMs are very useful for the study of water and environmental systems, such as the systems in the AquaStress test sites in an integrated way. Indeed environmental systems are usually multicomponent, nonlaboratory controllable, multivariate, multidisciplinary, nonlinear and complex. Analytical equations are rarely available for the system as a whole, although they exist for some system components. Conceptual and compartmentalized approached is often the only way to tackle them, and DSM offers the means of performing integrated simulation.
Pertinent participation process phase(s)
1- Starting organization
2- Actors analysis, context
3- Diagnostic of the current situation
4- Search of solutions
5- Implementation, evaluation
Application method
Developing simulation models for each test site to use as tools for performing simulations of each system as a whole.
The methodology used for SDMs consists of the following main steps, which will also be followed for AquaStress:
- Identify the problem (for each test site);
- Develop a dynamic hypothesis explaining the cause of the problem;
- Build a computer simulation model of the system at the root of the problem, using the specific modelling environment provided by the SDM tools;
- Test the model, to make certain that it represents the behaviour seen in the real world;
- Use the model to devise and assess alternative policies that alleviate the problem;
- Implement the solution
Application example(s)
Various examples in literature. For more information ask:
L.S.Vamvakeridou-Lyroudia@ex.ac.uk or D.A.Savic@ex.ac.uk
Example tools
- STELLA (www.iseesystems.com)
- VENSIM (www.vensim.com)
- POWERSIM (www.powersim.com)
- MODELMAKER (www.modelmakertools.com) (BORLAND)
- SIMULINK(www.mathworks.com) (MATLAB)
- SIMILE (www.simulistics.com)
There exist also some tools that can be directly implemented in GIS environment, using custom (higher level) modelling language - PCRASTER (www.pcraster.nl)
- SIMARC(www.ecoap.unina.it/software.htm) (linked to SIMILE).
AquaStress contact(s)
Contact: Lydia Vamvakeridou, University of Exeter (L.S.Vamvakeridou-Lyroudia@ex.ac.uk) or Dragan Savic, University of Exeter (D.A.Savic@ex.ac.uk)
Reference
-
Ford, A., 1999, Modelling the Environment: An Introduction to System Dynamics Modelling of Environmental Systems, Island Press, Washington D.C. ,U.S.A.
- Kapelan, Z., Savic, D.A. and Walters, G.A., 2005, CoDES Scoping Study, WP2 Literature Review: Decision Support Tools for sustainable urban development, Report No.2005/01, Centre for Water Systems, School of Engineering, Computer Science and Mathematics, University of Exeter, Exeter, U.K., 112p.
- Mazzoleni, S., Rego, F., Giannino, F. and Legg, C., 2004, Ecosystem Modelling: Vegatation and Distrurbance, in Environmental Modelling: Finding Simplicity in Complexity (Eds. Wainwright J. and Mulligan M.), John Wiley & Sons Ltd, West Sussex, England, U.K., 171-186.
- Mulligan, M. and Wainwright, J., 2004, Modelling and Model Building, in Environmental Modelling: Finding Simplicity in Complexity (Eds. Wainwright J. and Mulligan M.), John Wiley & Sons Ltd, West Sussex, England, U.K., 7-73.



