Held annually since 2005, this session is
focusing on general research of lakes, as well as the inland seas. The
event is intended as interdisciplinary between hydrology, limnology and
oceanography. Its scope encompasses physical, chemical, and biological
aspects of lakes and inland seas, as well as their responses to global
change, and offers a forum for both observational and modeling studies.

This session provides a scientific platform for exchange of findings from research that addresses the entire continuum of river and sea. We invite studies across geographical borders, along the freshwater-marine water continuum, and interdisciplinary studies that integrate physical, chemical, biological, geological observations/experiments, and modelling, and those that span the traditional silos of natural and social sciences.
River-Sea-Systems comprise river catchments, estuaries/deltas, lagoons and the coastal seas. They are dynamic products of interacting environmental and socio-economic processes. River-Sea-Systems provide natural capital and related ecosystem services that are fundamental to societal wellbeing. These systems, however, face compounding pressures from natural forces such as climate change and natural hazards, and from anthropogenic forces like urbanisation, shipping, energy generation, industrial development, water abstraction and damming, operating at local, national and global scales. The resulting pressures contribute to societal challenges such as eutrophication, hypoxia, pollution, change in hydrodynamics and morphodynamics (including disturbed sediment balances), loss of biodiversity, habitat depletion, sea level rise, and ultimately loss of ecosystem services. This impacts not only on the ‘planet’ but also on ‘people’ and ‘profit’. These pressures are likely to increase in the future with implications throughout the river-sea continuum with uncertain consequences for the resilience of the socio-ecological system.
We need to fully understand how River-Sea-Systems function. How are River-Sea-Systems changing due to human pressures? What is the impact of processes in the catchment on marine systems function, and vice versa? How can we discern between human-induced changes or those driven by natural processes from climate-induced variability? What will the tipping points of socio-ecologic system states be and what will they look like? How can we better characterise river-sea systems from the latest generation Earth observation to citizen science based observatories. How can we predict short and long term changes in River-Sea-Systems to manage them sustainably? What is the limit to which it is possible to predict the natural and human-influenced evolution of River-Sea-Systems?
Which policy responses would be desirable from a scientific perspective and how will the gaps between the existing European environmental policies be bridged (e.g. Water Framework Directive 2000, Marine Strategy Framework Directive 2008 and EU biodiversity policies)? How will links be made to the UN 2030 Agenda’s Sustainable Development Goals 6 (Clean Water & Sanitation) and 14 (Life below Water)?
The increasing demand to jointly enable intensive human use and environmental protection in river-sea systems requires holistic and integrative research approaches with the ultimate goal of enhanced system understanding. It is becoming widely recognised that there is a need to study River-Sea-Systems as an entire continuum, to provide scientifically underpinned information to enable better-informed and holistically engaged environmental protection of River-Sea systems, to maintain their ecosystem functioning and thus their capacity to provide ecosystem services.

Ecohydrology as a field of research is expanding rapidly and in the process is displacing boundaries of consolidated disciplines. The mobility of the research frontier is both exciting and challenging, especially in terms of defining what is presently encompassed by ecohydrology. This session aims to draw examples from the wide field of ecohydrology in order to portray the current diversity and common features of research frontiers in ecohydrological studies. This year we are especially interested in presentations that explicitly couple ecological and hydrological processes at the catchment scale, explore how vegetation modifies catchment water and chemical cycling and how these processes combine to impact in-channel organisms. Presentations focusing on challenging problems such as the arrangement of ecosystem structure and responses of organisms to hydrological drivers are also encouraged

Evapotranspiration (ET) is a key process in the hydrological cycle. A sound understanding and quantification of ET is an integral part of understanding and predicting the water balance changes due to land use and climate change. Estimating ET is prone to large uncertainties, and advances in measurements of transpiration as well as evaporation are sorely needed, both for system understanding and for validation of remotely sensed products and improving models. The latter requires upscaling from point measurements to spatial estimates which remains a crucial challenge in (eco-)hydrological modelling.

This session will mainly focus on the measurement of ET with in-situ devices like lysimeters, sap flow sensors, eddy covariance, scintillometers, Bowen ratio method and other approaches. Additionally, we want to address the spatio-temporal scale gap between the various in-situ approaches themselves as well as between in-situ data, remote sensing products and catchment-scale modelled ET. We thus welcome contributions that (1) assess and compare the quality of known and new in-situ ET measurements, (2) analyse ET trends in time series and ET spatial patterns and their controls, (3) include cross-scale comparisons and scaling approaches and (4) incorporate in-situ measurements into modeling approaches.

For other ET sessions, with a focus on catchment hydrology, especially in extreme and sensitive environments, see HS2.1.1; with a focus on arid and semi-arid environments, see HS6.5.

During the passage of precipitation through the soil-plant-atmosphere interface, water and solutes are redistributed by the plant canopy, subsurface flow and transport processes. Many of these dynamic interactions between vegetation and soil are not yet well understood. This session brings together the vibrant community addressing a better understanding of ecohydrological processes taking place between the canopy and the root zone. Innovative methods investigating throughfall, stemflow, hydraulic redistribution, and root water uptake in various environments shed light on how water and solutes are routed in the thin layer covering the terrestrial ecosystems. The session further covers open questions and new opportunities within the ecohydrological community regarding methodological developments such as the analysis of stable isotope, soil moisture, throughfall or solute dynamics.

Invited speakers:
Daniele Penna (University of Florence, Italy)
Darryl Carlyle-Moses (Thompson Rivers University, Canada)

Peatlands develop in specific hydrological settings and react sensitively to changes in climatic and hydrological boundary conditions. The hydrology of peatlands is fundamental to their function and development. Soil hydrological properties can change drastically after human interventions such as drainage, causing challenges for both model parameterisation and re-wetting measures. Pristine peatlands offer and regulate a number of ecosystem services such as biodiversity, carbon storage and nutrient retention. Hydrology is a key control for a number of these services but studies on peatland hydrology are surprisingly scarce. Furthermore, the effects of peatlands (both pristine and disturbed) on flood retention and on regional climate are much debated, but there seem to be more myths than data. As hydrological and biotic processes in peatlands are strongly coupled, estimating the eco-hydrological response of peatlands under climate change and linking it to vegetation development and greenhouse gas emissions is a demanding task for modellers.
This session aims to bring together peatland scientists to focus on improved understanding of hydrological processes operating in all types of peatlands. Peatlands being considered may be pristine or disturbed and degraded and may also include rehabilitation and re-wetting interventions. Hydrological data may have been collected for other reasons (e.g. carbon flux calculations) but the session welcomes re-examination of such hydrological data in its own right or as supporting data for other studies. Results from research focussing on all aspects of peatland hydrology are welcome in this session. Our scale of interest ranges from the plot to the regional scale. Field, laboratory or modelling studies on hydrological, hydrochemical or geophysical topics are welcome. Studies examining hydrological ecosystem service provision such as nutrient retention or flood protection would be welcome.

Groundwater-surface water interfaces (e.g., hyporheic and benthic zones and riparian corridors) are integral components of the aquifer-river or aquifer-lake continuum. Interactions between groundwater and surface water lead to strong bi-directional influences between surface waters, aquifers and interconnecting hyporheic zones. A rapidly expanding number of research projects are now investigating the implications of hyporheic exchange on the transport and transformation of nutrients and contaminants within river networks, and on controls to heat, oxygen, and organic matter budgets available to microorganisms and macroinvertebrates in streambed sediments. However, there is still a need to better understand the links between physical, biogeochemical, and ecological process dynamics in groundwater-surface water interfaces and their implications for fluvial ecology or limnology, respectively. Furthermore, it is important to consider the response of hyporheic exchange fluxes to environmental and climatic controls at different spatial and temporal scales (e.g. river channel, alluvial aquifer, regional groundwater flow). We consider up- and downscaling and the development of a general conceptual framework and improved process understanding for groundwater-surface water interfaces as among the most urgent challenges of hyporheic zone research. Consequently, we particularly welcome contributions that aim to close these knowledge gaps and solicit both experimental and modelling studies with a focus on:

- The development and application of novel experimental methods to investigate physical, biogeochemical and ecological conditions at the groundwater-surface water interface in rivers, lakes, riparian corridors, and wetlands;

- Investigations of the role of hyporheic processes for the retention and natural attenuation of nutrients and pollutants, particularly with respect to impacts on surface water and groundwater quality;

- Hydrological, biogeochemical and ecological modelling approaches (e.g. transient storage models, coupled groundwater-surface water models etc.);

- Investigations of the implications of groundwater-surface water interactions for management and risk assessment frameworks with regard to the European Water Framework Directive.

In recent years there has been a growing emergence of interdisciplinary research areas concerned with investigating the dynamic and multifaceted interactions between biotic and abiotic components of aquatic ecosystems. Such is the acknowledged importance of these interactions, that quantifying and understanding the two-way feedbacks of interacting abiotic and biotic components is recognised as a key contemporary research challenge. However, the different terminology used by various disciplines highlights the separation rather than the overlap between disciplines. Further, in many instances the creation of new sub-disciplines (or research areas) is not developing the study field, but arguably is leading to the ‘reinvention of the wheel’ in parallel disciplines. Changing the traditional perspectives by bridging the gaps between disciplines is therefore key to bring considerable advances in aquatic research.
This session focuses on bringing together scientists from different backgrounds dealing with the effects of environmental (both biotic and abiotic) stressors on the aquatic biosphere, from individual organisms through to whole ecosystems with the aim of simulating truly interdisciplinary research. Several temporal scales ranging from a single event (e.g. response to hydropeaking, predatory attacks) to long term evolution (e.g. adaptation to climate change, ecosystem modification) may be considered. We expect strong contributions from researchers transcending a variety of disciplines such as geomorphology, engineering, ecology and environmental sciences. Emphasis is given to studies dealing with stressors driven by climate change or anthropogenic activities. In this context we particularly welcome contributions on consolidated or novel measurement techniques and modelling tools to assess the effects of environmental stressors (e.g. flow modifications, habitat alterations) on biota, such as vegetation, macroinvertebrates and fish, that cross disciplinary boundaries.

The session will include an invited keynote by Prof. Markus Holzner from ETH Zürich.

The last two decades have brought a major technological advancement in collection of water quality and biogeochemical data in rivers, lakes and engineered systems using automated in situ wet-chemistry analysers, optical sensors and lab-on-a-chip instruments. Furthermore, our ability to characterise different fractions of natural organic matter has increased thanks to a range of analytical methods e.g. fluorescence and absorbance spectroscopy, mass spectrometry and chromatography combined with new data mining tools (Self-organising maps, PARAFAC analysis). Matching the water quality measurement interval with the timescales of hydrological responses (from minutes to hours) led to discovery of new hydrochemical and biogeochemical patterns in streams along with improved understanding of the underlying processes e.g. concentration-discharge hysteresis and diurnal cycling. We are now at the frontier of further advancing this understanding for a wide range of solutes and particulates in streams, rivers and lakes using rapidly developing technology of wet-chemistry analysers, optical sensors and lab-on-the-chip instruments. We need to understand better how organic matter links with other biogeochemical cycles (e.g. phosphorus, nitrogen, sulphur and iron) and processes in aquatic systems. In particular there is a growing need to monitor the advances in application of novel organic matter characterisation tools, understanding the origins, pathways, transformations and environmental fate of organic matter in aquatic environments and identification of robust numerical and statistical tools for data processing and modelling. This is an exciting opportunity to gain new knowledge of hydrochemical and ecological functioning of freshwater and engineered systems.

Previously in this session:
EGU 2018:
https://meetingorganizer.copernicus.org/EGU2018/session/26401

EGU 2017:
http://meetingorganizer.copernicus.org/EGU2017/session/24958

EGU 2016:
http://meetingorganizer.copernicus.org/EGU2016/session/20013

EGU 2015:
http://meetingorganizer.copernicus.org/EGU2015/session/17101
Keynote lecture: Diane McKnight

EGU 2014:
http://meetingorganizer.copernicus.org/EGU2014/session/15261
Keynote lecture: Darren Reynolds

Cities all over the world are facing rising population densities. This leads to increasing fractions of built-up and sealed areas, consequencing in a more and more altered and partly disrupted water balance - both in terms of water quantities and qualities. On top, climate change is altering precipitation regimes.

This session focuses on according urban ecohydrological problems and approaches to solve them spanning from technical to nature-based solutions in different time and spatial scales from the building to the whole city.

Ongoing climate change and a shorter return period of climate and hydrological extremes has been observed to affect the distribution and vitality of ecosystems. In many regions, available water is a crucial point of survival. Risk can be enhanced by the exposure and/or by the vulnerability of the affected ecosystem.
The session focuses on the complex assessment of all determining factors through a joint utilization of a broad spectrum of databases and methods (e.g. field and laboratory measurements, remote sensing, modelling and monitoring techniques) that can provide a suitable basis for developing long-term strategies for adaptation.
The session should provide a multidisciplinary platform for sharing experiences and discussing results of local and catchment scale case studies from a wider range of relevant fields such as
• observed impacts and damage chains in natural ecosystems induced by climate and hydrological extremes;
• correlation between the underlying environmental factors (e.g. climate, water holding capacity, soil characteristics) and the distribution/vitality of ecosystems;
• integrated application or comparison of databases and methods for the identification and complex assessment of ecosystem responses to abiotic stress factors;
• expected tendencies of abiotic risk factors affecting and limiting the survival of the vulnerable species.
Contributions are encouraged from international experiences, ongoing research activities as well as national, regional and local initiatives.

Globally, 10–20% of peatlands have been drained for agriculture or forestry, and they emit close to 5% of global anthropogenic CO2 emissions. There are countries in Europe that have more than 60% of their agricultural emissions originating from cultivated organic soils, and the fate of South-East Asian peatlands is of global concern. Drainage causes losses of specialized species and further ecosystem services such as nutrient retention. However, most peatland-rich countries address peatlands poorly in national emission reporting and climate change mitigation strategies.
Innovative mitigation measures that sustain economically viable biomass production while reducing negative environmental impacts including greenhouse gas emissions, fire risk and supporting ecosystem services of organic soils are currently vigorously studied. Management measures include, but are not limited to, productive use of wet peatlands (“paludiculture”), improved water management in conventional agriculture and innovative approaches in conservation-focused rewetting projects. Production systems where peatland water table is 40 cm below the surface or higher, can generate food (e.g. fish, berries, mushrooms), feed (e.g. fodder for livestock), fiber (for construction, furniture) and fuel, and raw materials for chemical industry. How to implement these innovations in practice and integrate them into national GHG inventories remains a challenge.
We invite studies addressing peat-preserving management practices on organic soils as well as their implementation into GHG inventories. Work on all spatial scales from the laboratory to the national level addressing biogeochemical as well as biological aspects and both experimental and modelling studies are welcome. Especially research on development of traditional systems with details on commodities with viable value chains and income generation would be of interest. Furthermore, we invite contributions that address policy coherence and identify policy instruments for initiating and implementing new management practices on organic soils.
This session is organized as a joined effort of Global Research Alliance “Peatland Management” working group, Global Peatlands Initiative, Greifswald Mire Center, Thünen Institute and RePeat (REstoration and prognosis of PEAT formation in fens - linking diversity in plant functional traits to soil biological and biogeochemical processes 2016-2019; BiodiVErSA) and PeatWise (Wise use of drained peatlands in a bio-based economy: development of improved assessment practices and sustainable techniques for mitigation of greenhouse gases 2017-2020; FACCE ERA-GAS) – projects.