Metamodel for the Medina del Campo Groundwater Body

Description

The Medina del Campo groundwater body is described by a set of models that do not talk to one another: a regional three-dimensional groundwater flow model, a water balance and allocation model, a local-scale recharge model, the physical assessment of groundwater-related ecosystem services, a regional economic model and a model of how the decision agents behave and interact. Each is authoritative in its own domain and unusable in combination, because the whole set takes far longer to run than a decision-making process can wait.

The metamodel resolves that. It is a System Dynamics model built with stocks, flows and feedback loops, in which the behaviour of the biophysical, economic and social models is reproduced in a simplified and rapid form, at a coarser resolution, in a single runnable object. Physical, socio-economic and climatic data are connected within it, and the structure was built through group model building so that the variables and the connections reflect the stakeholders' own understanding of the system as well as the modellers'.

It is the instrument that makes integrated assessment possible in the room. Scenarios can be run during a workshop, and the effect of an intervention on water levels, on abstraction, on crop economics and on the wetland ecosystems can be read together rather than in sequence.

Applications to decision making in the insurance sector

The metamodel is what makes the chain from intervention to outcome inspectable by a body that is not itself a modelling institution. For a risk carrier being asked to recognise a recharge or demand-management measure, the ability to see how a change in abstraction propagates to the water table, to the wetland, to the economy of the basin and back is the difference between accepting a claim about risk reduction and having to take it on trust.

Added value of this modelling approach

It trades resolution for speed deliberately, and it is honest about doing so. That trade is what allows integrated assessment to occur within a decision process rather than after it, and it makes uncertainty a subject the participants can discuss rather than a caveat appended to a result.

What decision can be improved with this modelling approach

Which combination of recharge, demand management and cropping change stabilises the aquifer at an acceptable cost; how long the system takes to respond; and how the benefits and costs fall between the irrigators, the water authority, the municipalities and the ecosystems.