“…An increasingly popular global-sensitivity approach is the method of active subspaces (e.g., Constantine et al, 2014;Constantine and Diaz, 2017). While been designed for engineering applications (e.g., Constantine et al, 2015a, b;Hu et al, 2016;Glaws et al, 2017;Constantine and Doostan, 2017;Hu et al, 2017;Grey and Constantine, 2018;Li et al, 2019), it has recently been used with good performance in hydrology (e.g., Gilbert et al, 2016;Jefferson et al, 2015Jefferson et al, , 2017Teixeira Parente et al, 2019), including a recent study of ours (Erdal and Cirpka, 2019).…”