Constructing a global hydrogeological database and a model builder framework for coastal salinity and subsidence modelling

Saltwater intrusion in coastal aquifers is a common threat to fresh groundwater resources worldwide. This threat has been intensified in recent decades by over-exploitation, reduced groundwater recharge, subsidence and more frequent coastal flooding. Computer modelling is a commonly used by water management bodies to simulate saltwater intrusion in coastal aquifers. However, input data and modelling tools often lack in developing regions which would therefore benefit from a simple open source toolbox to quickly assess the current (and future) saltwater intrusion in given region.

To this end, we create a framework that provides a wide range of potential users with tools to quickly set up coastal groundwater flow models using the SEAWAT code. This allows users to analyze groundwater salinization in any coastal area around the world under various temporal, boundary and topographical conditions. The developed framework is built on previous research into global coastal geological heterogeneity and global coastal groundwater modelling. The framework was implemented into the powerful open source QGIS as a plugin, which is easily accessible by the public. This allowed us to focus more on the groundwater modelling tools themselves while using the GIS functionalities of QGIS.

We chose to call the framework SWAMPy-tools which stands for Salt Water intrusion Analysis and Modelling Python plugin for QGIS. The users can either use preexisting models to visualize the groundwater conditions in a given coastal region, or build their own groundwater model from scratch in a step-by-step model builder approach. In succeeding tabs the user will first define the location of the model, its geometrical extent and its grid discretization (2D only so far). Next, the geological conditions can be specified, using either pre-existing information based on global datasets or user defined information. In the final stages the initial conditions, boundary conditions and SEAWAT parameter values are defined. Once the model is setup, which should take on average several minutes or tens of minutes, the user can test the model by performing a test run (one short stress period) to check if there are any errors in the model setup; this is an optional step by recommended to save time in debugging the model. When everything is in order the user can finally run the model (the calculation itself is performed outside the QGIS environment) and when the model is finished the results can be loaded and visualized in the plugin as well.

We hope that the SWAMPy-tools QGIS plugin will be used by the groundwater modelling community across academic and private institutions. Any feedback and ideas for new features are always welcome of course!