In this study, we investigate how removing water from beneath glaciers influences their water pressure and flow speed. Using a numerical model of Helheim Glacier, Greenland, and Thwaites Glacier, Antarctica, we find that extracting water from under the ice can moderately slow glaciers by lowering subglacial water pressure. Our work improves understanding of glacier dynamics and suggests that studying water removal could enhance knowledge of subglacial systems and potentially slow glacier flow.