Calibration of simulation platforms including highly interweaved processes: the MAELIA multi-agent platform

The MAELIA project develops an agent-based modeling and simulation platform to study the environmental, economic and social impacts of various regulations regarding water use and water management in combination with climate change. An integrated modelling approach has been used to model the investigated social-ecological system. MAELIA combines spatiotemporal models of ecologic (e.g. water flow and plant growth) and human decision-making processes (e.g. cropping plan), socio-economic dynamics (e.g. land cover changes). Due to the diversity and the interweaving of the processes considered, the calibration and evaluation of such a multi-agent platform is a scientific challenge. Indeed, many parameters can reveal to be influential on the model outputs, with a high level of interactions between parameters impacts. In order to get an overview of the model behaviour and to screen influential parameters, multiple sensitivity analyses were performed, while considering some sub-sets of processes or not. This step-by-step sensitivity analyses enabled to disentangle the different influences and interactions, and was a preliminary step to the calibration process. In our case, the calibration, which is a multi-objective (e.g. reproducing water flows and anthropic dynamics, traduced by different numerical criteria such as joint use of L 2 -norm with variance-covariance matrix and indices of squared errors on water crisis temporality) optimization problem, was achieved thanks to metamodels built on an appropriated design of experiments.