Surface Water

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Continuous nutrient sensing in research and management: applications and lessons learned across aquatic environments and watersheds

This special section is concerned with the use of high-frequency sensors for nutrient monitoring and research in freshwater and coastal systems. Nutrient pollution, along with resulting eutrophication, hypoxia, and harmful algal blooms, is one of the most significant environmental problems facing the world today. Continuous nutrient sensing is on the cusp of being a widely employable technique for collecting data on in-water nutrient concentrations (primarily dissolved forms of nitrogen and phosphorus) to help inform management and mitigation efforts and as tools for fundamental research. As new sensors continue to be developed and used in a variety of applications and environments spanning the water cycle, analyses and data interpretation from early adopters of these technologies will be critical to guiding their future use for research and management.

Concentration-discharge relations in the critical zone

Critical Zone scientists seek to develop mechanistic-predictive theory of critical zone structure, function, and long-term evolution. One postulate is that contemporaneous hydrochemical controls over all three can be related quantitatively to dissipative solute releases measured down-gradient of reactive flow paths.These flow paths have variable lengths, compositions, and residence times, and their mixing is reflected in concentration-discharge (C/Q) relations.It is recognized that contemporaneous measurements are only that, and don’t necessarily reflect C/Q behavior over the course of CZ evolution. Motivation for this special section originates from a U.S. Critical Zone Observatories workshop that was held at the University of New Hampshire, July 20-22, 2015.The workshop focused on resolving mechanistic CZ controls over surface water chemical dynamics across the full range of lithogenic (e.g., non-hydrolyzing and hydrolyzing cations and oxyanions) and bioactive solutes (e.g., organic and inorganic forms of C, N, P, S), including dissolved and colloidal species that may co-occur for a given element. Papers included in this special section utilize information pertaining to internal, integrated catchment function (relations between hydrology, biogeochemistry and landscape structure) to help shed light on controls over observed C/Q relations.

Emergent aquatic carbon-nutrient dynamics as products of hydrological, biogeochemical, and ecological interactions

Carbon-nutrient dynamics in aquatic systems, such as rivers, lakes and wetlands, represent emergent responses from complex interactions among hydrological, biogeochemical and ecological processes. For example, hydrologic flow paths and residence times are connected closely to attendant biogeochemical processing of carbon and nutrients (e.g., nitrogen, phosphorous, sulfur). These, together with other interconnected processes (e.g., human activities, aquatic ecological dynamics), organize biogeochemical patterns across various aquatic systems at a range of spatiotemporal scales. A coherent understanding synthesized from different physical and biological disciplines is therefore necessary to interpret and predict the complex and often non-linear behavior of aquatic systems. In this special issue are contributions that investigate hydrological, biogeochemical, and ecological interactions--particularly those involving carbon-nutrient dynamics--and that provide insight to the functioning of these linked systems from interdisciplinary perspectives. Continued progress in this research area will depend on cross-disciplinary research that spans spatial and temporal scales, incorporates field-based and modeling components, and bridges gaps between physical and biological sciences.

Specifically, this special issue includes research including, but not limited to: 1) Fundamental concepts of how complex hydrological, biogeochemical, and ecological systems interact and visionary paths toward conceptualizing these interactions; 2) Studies that link these processes across the terrestrial-aquatic interface; 3) Advances in in-situ and large scale observation, characterization and interpretation of critical processes in complex hydro-biogeochemical systems; and 4) Conceptual and numerical models to describe and predict the non-linear dynamics of hydro-biogeochemical systems under contemporary and future climate conditions.

Climatic, Hydrological, and Land Use Impacts on Large Rivers

1 May 2014
H. Habersack
Rivers provide mankind with key benefits, such as water supply, food, hydropower, navigation, irrigation, ecosystem services, and recreation. They are fundamental to life and frequently possess major cultural significance. However, they are currently threatened by unsustainable "overuse", increasing human pressure on their catchments, and problems of increased floods and droughts driven by climate change, leading to changes in morphology, increased pollution, degradation of aquatic habitats, extinction of fish species etc. All these changes detract from the many benefits that rivers provide to mankind and rivers' continuing contribution to human needs. In order to discuss these threats and challenges, AGU intends to publish a special issue of Water Resources Research under the title "Climatic, Hydrological, and Land Use Impacts on Large Rivers," collecting and consolidating those conference papers from the World's Large Rivers Conference 2011 which focus on adaption strategies and the development of new methods to determine and mitigate hydrological alterations of large river systems in a changing environment.

Recent Loch Vale Watershed Research

1 January 2000
Catchment-scale intensive and extensive research conducted over the last decade shows that our understanding of the biogeochemical and hydrologic processes in subalpine and alpine basins is not yet sufficiently mature to model and predict how biogeochemical transformations and surface water quality will change in response to climatic or human- driven changes in energy, water, and chemicals.

Reynolds Creek Experimental Watershed

1 November 2001
To understand how variations in climate, land use, and land cover will impact water supply and water quality, we must have access to long-term hydrologic and climatic databases. The National Research Council [1999] recognized the value of experimental watersheds as the setting for the development of our current understanding of physical and biological watershed processes.

Chapman Conference on Hydrogeochemical Responses of Forested Catchments

1 December 1990
From September 18 to 21, 1989, the American Geophysical Union (AGU) sponsored a Chapman Conference on Hydrogeochemical Responses of Forested Catchments. Approximately 130 hydrologists, geochemists, soil scientists, ecologists, and other scientists involved in research on forested catchments presented results of their investigations and discussed the state of knowledge regarding hydrological and geochemical processes that control catchment response.