Training in uncertainty assessment of groundwater flow and solute transport modelling, and automated calibration of groundwater flow models

Venue: Geological Survey of Denmark and Greenland (GEUS), Copenhagen, DK

Attendees: Željka Brkić (HGI-CGS), Maja Briški (HGI-CGS) and Ozren Larva (HGI-CGS)

GEUS experts: Anker Lajer Højberg, Ida Karlsson Seidenfaden, Simon Stiesen, Julian Koch, Per Rasmussen

Duration: October, 28 – October, 31 2019

During the 1st day of the training GEUS staff gave an overview of their experience dealing with uncertainty assessments of hydrological models with the focus on sources of uncertainty and how to address different uncertainties in hydrological models. It was followed by exercise on identification of relevant sources of uncertainties and uncertainty assessment for the Zagreb pilot.

In the beginning of the second day HGI-CGS staff presented the status of the steady-state and transient groundwater flow models of the Zagreb pilot area. Special attention was attributed to the convergence difficulties of the transient model. The rest of the morning was used for the discussion on the aims of the Zagreb area model and how to frame scientific questions for proposed papers. In the afternoon, GEUS and HGI-CGS staff worked together on setting up and execution of PEST for the modified version of steady-state model of the Zagreb pilot area. Additionally, a thorough check-up of MODFLOW input and output files was performed in order to achieve the convergence of the transient model, which was successfully done by the end of the day.

The third day was dedicated to parallel PEST for transient groundwater flow models. In the beginning, GEUS staff gave a theoretical background, which was followed up by exercise on calibration of transient models. It was also necessary to modify Python scripts, originally made for steady state simulation, in order to perform correctly in the course of transient simulation.

During the last day of the training HGI-CGS and GEUS staff continued the work on automatic calibration of transient groundwater flow model, including the detailed analysis of input and output PEST files. In addition, different approaches to optimization of automatic calibration process were discussed, including model gird modification and time step control.

A wrap-up meeting was held at the end of the visit, where future short-term actions were discussed and agreed.