Themes:
1. Advances in remote sensing data processing and products
1.1. Advances in EO-based retrievals of hydrological surfaces and sub-surface variables: water body extension and water surface elevation, snow cover, snowmelt, snow water equivalent, soil moisture, groundwater storage, total water storage, river discharge, total runoff, evaporation, and water quality.
1.2 Advances in atmosphere satellite-based observations, precipitation, clouds, and water vapour.
1.3 Cal/Val of present and future missions: methods and in-situ data.
2. Advances in the use of EO for land surface and hydrological modelling
2.1 Advances in EO integration (data assimilation, model calibration etc.) in hydrological and land surface models and digital twins.
2.2 Advances in high-resolution hydrology: modelling and EO data challenges.
2.3 AI/ML-based and data-driven modelling in hydrology (foundation models, embeddings etc.).
3. Advances in hydrological process understanding and modelling across scales
3.1 Empirical evidence, process understanding, and attribution of water cycle responses to climate variability and climate change, from local to global scales.
3.2 Observing, quantifying, and attributing the impacts of anthropogenic water use, water management, and land use/land cover change on hydrological processes across scales.
3.3 Understanding the carbon-water-energy nexus.
4. Water science for society
4.1 Advances in observation, characterisation, and prediction of hydro-climatic hazards (floods, droughts, landslides), their compound and cascade events, and the post-event recovery.
4.2 Operational water resource/quality management and decision support systems: real-time monitoring, forecasting, and integration of EO data into water allocation, reservoir operations, irrigation scheduling, etc.
4.3 EO for water policy and governance: monitoring frameworks for water quality, water security, and national/international water regulations and transboundary agreements.
4.4 Co-development and stakeholder engagement: co-design of EO-based services and solutions with water managers to ensure operational relevance and uptake.
4.5 Capacity building, knowledge transfer, and application in data-scarce regions.
5. Novel technologies and upcoming missions: the future of water cycle research
5.1 Future EO missions and observing capabilities for water and hydrology research and applications. Preparing new operational and pathfinder missions (commercial, new space and sovereign capabilities for meteorology and hydrology).
5.2 Novel technologies and software for water and hydrology research and applications. Developing innovative technologies, algorithms, and tools for improved EO data exploitation and hydrological monitoring.