Physical assessment of groundwater dependent Wetland Ecosystem Service

Description

The wetlands of the Medina del Campo groundwater body — the lagunas and wet meadows fed by the shallow water table — are the visible expression of the aquifer's state. Where the water table has dropped, they have contracted or disappeared; where it remains shallow, they persist. This model assesses the ecosystem services they provide in physical, measurable terms.

The assessment begins with the hydrological connection: the depth to the water table beneath each wetland, its seasonal variation, and the flooding regime that the vegetation depends on. From that it derives the services the wetland performs — water regulation, the attenuation of contaminants, habitat provision and the cultural and amenity values associated with a functioning wetland — and it establishes the threshold conditions beyond which each service degrades.

Because the service is a function of the water table rather than of the land cover, the assessment can be coupled directly to the groundwater models. A change in abstraction or a recharge intervention is translated into a change in water table depth, and that into a change in service delivery.

Applications to decision making in the insurance sector

Groundwater-dependent ecosystems are among the slowest systems to respond and to recover, which makes them a poor fit for short-horizon appraisal and a good fit for risk-transfer discussions. The assessment supplies the physical basis for treating the maintenance of the water table as prevention — a maintained water table removes a drought exposure that would otherwise be carried by the water users and, indirectly, by the public budget.

Added value of this modelling approach

It states the environmental benefit of a groundwater measure as a change in a physical service rather than as a habitat description, which is the form in which it can enter an economic assessment and be compared with the cost of the measure.

What decision can be improved with this modelling approach

How much water has to be left in the aquifer for the dependent ecosystems to function; which recharge sites deliver the greatest ecological benefit; and what the environmental cost of continued abstraction at current levels would be.