Ying Fan and groundwater's global impact

Hydrogeologists are trained to think about belowground processes, and their importance is apparent to them. Other scientific disciplines have traditionally emphasized processes that occur on or above Earth's surface, and thus groundwater's roles sometimes go unnoticed in studies of weather, climate, and plant diversity and traits, among others. Over her career, Ying Fan has persistently highlighted the critical importance of groundwater processes on global climate, surface hydrology, and vegetation as well as the need to improve the representation of these processes in Earth system models. Here, we review Fan's scientific contributions and frame them within some of the simple yet profound questions that she asks: How deep is groundwater? Where, when, and how does groundwater affect weather and climate? Where and when is groundwater a dominant driver of vegetation's spatial patterns across the landscape? How deep do roots grow? We examine these questions through the valuable insights gained from the work by Fan, her colleagues and mentees, and other works that preceded them, highlighting impacts of Fan's work on the scientific community.