Are the results of the groundwater model robust?

TL;DR

This paper critiques a groundwater model study, highlighting that its conclusions about environmental exhaustion are uncertain due to flawed assumptions and inadequate sensitivity analysis.

Contribution

It demonstrates that the previous model's sensitivity analysis is insufficient, emphasizing the need for better experimental design in groundwater modeling.

Findings

The original study's assumptions are non-unique and questionable.

Sensitivity analysis was poorly conducted and not conclusive.

Model conclusions about environmental exhaustion are not robust.

Abstract

De Graaf et al. (2019) suggest that groundwater pumping will bring 42--79\% of worldwide watersheds close to environmental exhaustion by 2050. We are skeptical of these figures due to several non-unique assumptions behind the calculation of irrigation water demands and the perfunctory exploration of the model's uncertainty space. Their sensitivity analysis reveals a widespread lack of elementary concepts of design of experiments among modellers, and can not be taken as a proof that their conclusions are robust.