Dear Colleagues,

Water quality in watersheds and waterbodies is a critical issue due to its direct influence on public health, the biological integrity of natural resources, and the economy. Anthropogenic influences on climate change and variability, land use, and land cover change at the watershed scale can have various impacts on the hydrological, biological, and chemical processes within freshwater watersheds, bringing significant changes in the water quality of rivers, lakes, and reservoirs. Water quality issues in watersheds and inland waterbodies eventually affect water quality in estuaries and oceans. The Earth has a tremendous variety of waterbodies, from small ponds to Lake Superior, and from humanmade reservoirs to natural lakes. Even though waterbodies are only a small part of our planet, they play a critical and important role in the Earth’s biosphere. Understanding the impacts of changes from upstream or surrounding watersheds on water quality is important to people who live or visit the waterbody and is also fundamental in providing better ecological and environmental strategies and mitigation methods to protect our ecosystems.

Dissolved oxygen and other water quality constituents have implications for the growth, reproduction, and survival of freshwater organisms such as phytoplankton, zooplankton, benthic organisms, and fish. Climate variations (seasonal or inter-annual) and global climate warming directly affect the heat budget of an aquatic system through the surface heat exchange between the water and the atmosphere and then influence water quality characteristics. Climate warming will alter water temperature, ice/snow cover, and water quality characteristics in aquatic systems. Nutrients and other chemicals to aquatic systems affect freshwater organism populations and biodiversity. Monitoring and modeling approaches have been used by citizen volunteers, biologists, water resources managers, engineers, and scientists to understand and study water quality issues in watersheds and waterbodies. Different monitoring techniques and modern monitoring devices/sensors allow us to get more in-depth information that we could not obtain before. Advanced models or modeling methods also allow us to better understand water quality dynamics and spatial distributions in watersheds and waterbodies that discrete data collections or monitoring cannot reveal. Over the last few decades, significant improvements in watershed models have been achieved to explore water quality modeling in waterbodies due to various anthropogenic interventions. Monitoring data are necessary for model calibration and validation before the model can be used for scenario study, sensitivity analysis, and future projection under certain changes in watersheds.

In this Special Issues, we would like to invite journal articles related to watershed- and waterbody-scale studies on water quality bringing innovative approaches to address the emerging environmental problems. The Special Issue covers recent advanced modeling and monitoring studies related to water quality and includes but is not limited to the following:

• Modeling and monitoring of point sources from urban areas and non-point source pollution from the agricultural land at the watershed scale;
• Development of new tools or the improvement of existing models to investigate and evaluate the consequences of point and non-point source pollution on the downstream water quality;
• Application of watershed models for small to large-scale watershed studies to simulate the water quality both at the surface and at the subsurface level to incorporate the environmental impact of land use development, and land management strategies;
• The studies of the nutrient losses from the agricultural land, instream nutrient transport processes, and in-stream water quality processes from the river;
• Innovative research to potentially improve the watershed models to address the complexity of watersheds in terms of better representation of land use change, forest management, agricultural best management practices, and various scenarios of real-world systems in watershed modeling to improve water quality;
• Modeling and monitoring the impact of land development and agricultural practices in the water quality in field-, watershed- and basin-scale studies;
• To identify the knowledge gap in watershed and waterbody modeling processes;
• The improvement of the watershed and waterbody models to integrate the advanced processes and new sciences for appropriate representation of land development and agricultural growth processes at the spatial and temporal scales within a watershed;
• Pollutant build-ups at the watershed scale and their impact on downstream water bodies;
• Development of models to incorporate the nutrient transport and various transformation processes of several forms of nutrients (nitrogen, phosphorus, etc.), plant growth, pesticides, bacteria, micro/nano plastics, and sediments at the watershed scale or inside waterbodies;
• Modeling and monitoring of emerging contaminants in the water cycle including, but not limited to, per- and polyfluoroalkyl substances (PFAS), perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS), which act as so-called endocrine disruptors (EDCs);
• Watershed- and basin-scale water quality assessment/projection under both existing and project land use and land management conditions;
• Development of management scenarios for water quality improvement in waterbodies using various best management practices;
• Research incorporating complex water quality processes at the watershed scale and developing scientific support tools for decision-making systems;
• Uncertainty in model application, sensitivity analysis of watershed and waterbody model parameters.

Both reviews as well as new research papers are welcome.

Prof. Dr. Xing Fang
Prof. Dr. Jiangyong Hu
Dr. Suresh Sharma
Guest Editors

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• watershed modeling of water quality
• water quality modeling in waterbodies
• water quality monitoring in watersheds and waterbodies
• anthropogenic influence
• climate change impact on water quality
• land use change impact