Freshwater is a rare resource that is vital for both environmental integrity and socio-economic viability; the intensification of agriculture, increasing energy needs, and rapid global urbanization, accompanying swift population growth, are also dramatically transforming the cycle of water. Practices associated with water management vary widely across the globe, but most fulfill human needs such as food and energy production, while having an often negative impact on the natural ecosystems, such as groundwater depletion, soil salinization, desertification, water quality degradation (e.g. algal bloom), and loss of recreational value and biodiversity. Accelerating anthropogenic climate change adds additional uncertainty to changes in the spatial and temporal distributions and the quantity and quality of water resources. To ensure that the water we enjoy today will still be clean and usable for the next generations, innovations and community-scale coordination in water use, assessment, and management are urgently needed.

As the fundamental unit of water management and planning, watersheds often comprise both terrestrial (e.g. grassland, forests, urban, and cropland) and aquatic ecosystems (e.g. streams, wetlands, and lakes), and water cycling is influenced by both land management (e.g. land use change and conservation) and riverine interventions (e.g. diversion and impounding). The proposed special issue (SI) particularly seeks novel contributions that couple terrestrial and aquatic processes to advance fundamental knowledge, analytic tools, assessment methods, and linkages between science and decision/policy making in watersheds with varying natural and socio-economic conditions. Given the interdisciplinary nature of water cycling and its management, the SI welcomes a broad array of topics that include, but are not limited to, climate change impacts on water cycle, surface–groundwater interactions, nutrients and carbon cycling along the land–river continuum, agricultural water management, the water–energy nexus, biofuel sustainability, and socio-economic assessment of water sustainability. Approaches combining process-based watershed models with in situ and large-scale geospatial data, as well as spanning multiple disciplines, are of particular interest.

By systematically rounding up and examining the latest advances in watershed-scale water resource studies across Earth’s critical regions facing diverse pressing water challenges, this SI is intended to provide the scientific community, water resource managers and policy makers with a repository of cutting-edge knowledge pertinent to water resource sustainability.

Research themes include but are not limited to

1. model development to better represent coupled terrestrial–aquatic processes influencing water cycling at the watershed scale;
2. water, nutrients, and carbon cycling in response to human interventions (e.g. anthropogenic climate change, land use/land cover change, and hydro-engineering);
3. the food–water–energy nexus at the watershed scale; and
4. socio-economic assessment of best water management practices.

The theme of the proposed SI is well in line with the scope of Hydrology and Earth System Sciences (HESS), which “encourages and supports fundamental and applied research that seeks to understand the interactions between water, earth, ecosystems, and humans”. Particularly, the SI is intended to attract novel interdisciplinary research, thereby contributing to HESS-encouraged “cross-fertilization across disciplinary boundaries” and enabling “a broadening of the hydrologic perspective and the advancement of hydrologic science”.