The quest for low-carbon energy sources is driving a wave of new hydropower dam construction throughout the world. This is particularly the case in mountain regions such as the Andes, where a very large, untapped potential for hydropower still exists. It is therefore essential to get a better grip on the side-effects of dam development, and their impact on water quality is a very important but highly understudied aspect of those. This is again particularly timely and relevant in tropical regions, which are facing a perfect storm of limited data availability, poorly understood processes, and major challenges for sustainable development.