This vital work by Bandhopadhyay and Modak (2022) addresses one of the most compelling dilemmas of our time: how do we conserve rivers now that they are stressed by climate change and growing human need for freshwater? It considers what is arguably the globe’s most important hydrological system—the 10 rivers that flow from the Hindu Kush Himalaya (HKH). The book explains that at least 2 billion people live in these basins, distinguished by a highland–lowland divide.