Abstract <p>The permafrost zone, encompassing vast areas of permafrost, is an important element of the global hydrological cycle, and plays a key role in the formation of polar runoff. Current studies of hydrological processes in permafrost regions face several limitations, including pronounced spatial heterogeneity and insufficient density of observation networks, particularly in small catchments that form the basis of the Arctic hydrographic network. Additional limitations are associated with the limited accuracy of hydrological models, which often fail to fully account for cryogenic processes, leading to high uncertainty in forecasts of the hydrological consequences of permafrost degradation. Despite significant progress in recent years—the development of international monitoring programs, the creation of global hydrological databases, and the widespread introduction of remote sensing and numerical modeling methods—a number of key problems remain. This review, the first part of the work, analyzes the current state of the hydrometeorological and geocryological monitoring system, as well as global databases used to study the hydrological regime of rivers in the permafrost zone. Key challenges in modern permafrost hydrology are highlighted, including insufficient observation density, modeling limitations, and high uncertainty in assessing the impacts of permafrost degradation.</p>