This is a very detailed report on a highly interesting hydrological expedition into the most upstream and mostly ungauged tributaries of the Zambezi River, one of the largest rivers of the African continent. It provides detailed observations of river discharge and water quality during several enterprising excursions following tributaries from the source to the main river confluence. It offers a unique hydrological resumé of an adventurous field campaign.

The Aral Sea represents both an example of large-scale environmental degradation caused by human activity and a message of hope through its partial restoration. This follow-up study emphasizes that while the system appears healthy at present, it lacks resilience and small perturbations could significantly alter the entire ecosystem. The topic of the paper is of broad interest and the results of the analysis are also important for the management of the region.

This social relevant work is innovative, well-thought-out, and technically sound. The study has the potential to support water management in an under-served region that would benefit from this kind of operational forecast system (Central Asia). Free public availability of the author’s code and all the required input data means the forecast model is easily implemented in production systems.

This study addresses the highly relevant issue of dam operation around the central question if dam operation can help to alleviate both floods and droughts, and under what conditions. This study of dams in Germany is highly relevant to water management in a climate with increasing frequency and magnitude of weather extremes.

This paper is the first to present a mechanism for greening of the Sahara that relies on westerlies intensity as the primary mechanism. This mechanism, which is based on cutting edge analysis and observations, has the potential to move the 30 year-long debate on African Humid Period forward. This interdisciplinary study joins several fields, including climatology, paleoclimate, remote sensing, and hydrology.

This study integrates deep learning techniques into hydrological modelling to reconstruct runoff data. The extended reconstruction of runoff spanning over six decades (1962-2023) provides an unprecedented data basis to study long-term runoff patterns and trends in Switzerland. The findings spotlight a shift towards less frequent wet years and more frequent dry conditions in Switzerland. This insight is also relevant given the current situation of extreme droughts and floods in Europe.

This paper uses information from news sites with natural language processing tools to infer data on a hydrological process at the regional scale (flooding). The paper demonstrates the technique's applicability and opens new avenues to use advanced computing techniques and web resources to improve the understanding of hydrological processes.

A rigorous analytical hydrological model for Ensemble Rainfall-Runoff Analysis (ERRA) of catchments. The paper gives the concepts, mathematical details and several proof-of-concepts. ERRA was designed as a tool for iterative and exploration of hydrological data, through trial and error with analyses of varying degrees of complexity. The broad geosciences community could benefit from this statistical approach. The discussion cites some good examples of applications possible in hydrology, but potential also in other related fields as well.

The paper includes a very rare 3 year data collection of stable water isotopes in surface and subsurface waters. The innovative analysis challenge general conceptualizations of new precipitation inputs wetting dry soils or displacing previously stored waters from those soils. These observations illustrate how measurements of isotopic variability across different subsurface depths, hillslope positions, and time scales can help to constrain potential flow processes delivering precipitation to deep soils and streams.

Large sample hydrology datasets such as Caravan provides the community with hydrometeorological information and catchment attributes for many catchments in the world and offers the opportunity for hydrological research. However, there are considerable differences between the forcing data of Caravan compared to the CAMELS datasets, especially with potential evaporation. This can lead to wrong conclusions on catchment hydrological drivers and affect regionalization. This papers shows the important of robustness of large sample datasets and the need to keep assessing that.

The subject of the paper is well outside the mainstream, and interesting for its methodological approach, the way it connects cave hydrology to air permeability of sedimentary rock, and the relevance for the protection (or lack thereof) of prehistoric cave art.

This paper is of great interest to the geoscience community and the broader public because it offers a comprehensive European flood event catalogue that merges historical records with modelled data, providing an extensive overview of coastal, riverine and compound flood impacts across Europe over seventy years. This will help enhance the accuracy and completeness of flood impact assessments, crucial for improving flood risk management and mitigation strategies. It also provides a milestone dataset for understanding changes in hazard, vulnerability and exposure for national, regional and continental flood risk assessments.

The topic is of interest to a wide audience. The authors have developed a new approach to assess changes in the spatial extent of flooding.

I think this paper may be worth highlighting because it provides a thorough description of a cross-disciplinary problem that has yet to be addressed in practice. The use of PTFs measured at small scales within global models represents a huge discrepancy. This paper challenges us to reconsider how we do things in this field.

This paper introduces recent methods to cluster catchments that is based on traits with an application on a very important dataset (over 9000 catchments using 274 traits). The method proposed open many research perspectives in the fields of hydrology, environmental sciences and other disciplines.

Freshwater is a precious commodity for mankind, and irrigation is one of the largest component of freshwater usage by mankind. Many uncertainties exist in determining the amount of freshwater usage for irrigation. This manuscript discusses various ways to quantify irrigation and application of remote sensing to assess irrigation fluxes. With future, high-resolution remote sensing platforms becoming available, this work will be helpful to develop application pertaining to irrigation quantification especially is drought affected and semi-arid regions of the world.

This review paper constitutes a tremendous effort reviewing and analyzing a vast body of literature on the evaluation of Satellite Remote Sensing-based evapotranspiration datasets. It is a great road map for this field of research guiding all future such studies toward the use of community-based best practices.

This paper is relevant and can be of interest for a wider audience. It is important that the effects of artificial snow on hydrology and water resources is discussed in a more technical, hydrological forum, like HESS. The paper shows important and sound conclusions which are relevant in the societal discussion on the effects of snowmaking.

This paper presents an open-source software package for earth observation data accessing, reformatting, and visualization. This tool can be useful to the broad science community and stakeholders for effective use of remote sensing products. It lowers the technical barriers and simplifies the process of accessing earth observation data. It works for multiple operating platforms.

The characterization of subsurface hydraulic properties of catchments is one of the grand challenges in hydrology. This study explores the potential of using the stream network for this issue. The idea is very innovative and deserves to be highlighted.

The study proposes a new approach to characterize soil hydraulic functions. The novel approach strongly improves simulation results. This is a significant advancement of vadose zone hydrology.

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.

Understanding how catchments respond to change is a central theme of the work of many hydrologists around the world, however, it is fair to say that the vast majority of these studies have focused on water quantity. This study is unique in that it represents a very detailed treatment of how water quality changes due to drought, which is a topic that is becoming ever so important with the rapid changes happening in warming climate for many regions of the world. The authors very cleverly combine both complex models and data-driven analyses to elucidate the effects of extreme drought on river water quality.

In agreement with the handling Editor, the study is highlighted in HESS

This work addresses the important issue of the "dry gets drier wet gets wetter" paradigm from a new perspective using terrestrial water storage estimates. The paper can be an important contribution to the debate on how climate change will impact the global distribution of aridity.