Despite covering over a third of Earth’s land surface, arid regions remain among the least understood hydrological environments. Practically every component of the desert water cycle is more poorly constrained than its counterpart in wetter regions. Yet deserts are home to over 20% of the global population and are disproportionately vulnerable to hydrometeorological hazards such as droughts, floods, and the accelerating impacts of climate change. A better understanding of the desert water cycle is therefore not only a scientific challenge, but a critical need for sustainable water resource and risk management in drylands.In this talk, I will present three studies that illuminate different aspects of the desert water cycle:(a) how satellite observations can be used to infer the (underwater) topography — and thus the water volume — of remote desert lakes;(b) what atmospheric ingredients link moisture, rain, and floods in the hyperarid Sahara, and how these relate to the desert's paleo- (and future?) climate; and(c) how misjudged flood risk management on the desert margin contributed to the deadliest hydrometeorological disaster of the 21st century in Derna, Libya.Together, these studies illustrate how unconventional combinations of satellite data and modelling can overcome the challenges of limited in situ observations to reconstruct, quantify, and ultimately understand hydrological processes in deserts. They also challenge longstanding assumptions about runoff generation and risk mitigation in arid regions, pushing the boundaries of what we thought we could know in some of the world's most water-scarce landscapes.
