Periodic Reporting for period 5 - DyNET (Dynamical river NETworks: climatic controls and biogeochemical function)
Periodo di rendicontazione: 2024-05-01 al 2025-04-30
Despite the ubiquity of expansion and retraction dynamics of flowing streams, river networks are often conceived as static elements of the landscape, and a coherent framework to quantify nature and extent of drainage network dynamics is lacking. The implications of this ubiquitous phenomenon extend far beyond hydrology and involve ecological and biogeochemical functions of riparian corridors, as well as policy actions for the protection of temporary streams. The research project will move beyond the traditional paradigm of static river networks to unravel physical causes and biogeochemical consequences of stream dynamics. In particular, the project plans to identify the climatic and geomorphic controls on the expansion/contraction of river networks, and quantify the length of temporary streams and their impact on catchment-scale biogeochemical processes and stream water quality.
These challenging issues aree addressed by developing a novel theoretical framework complemented by extensive field observations within four representative sites along a climatic gradient in the EU: i) the Rietholzbach catchment, in Switzerland; ii) the Valfredda catchment in Northern Italy; iii) the Montecalvello catchment, in Central Italy; iv) the Turbolo catchment in Southern ITaly. Field measurements performed include long-term high-frequency mapping of the active drainage network and daily hydro-chemical data across scales. The experimental dataset will be used to develop and inform a set of innovative modelling tools, including an analytical framework for the description of spatially explicit hydrologic dynamics driven by stochastic rainfall and a modular hydro-chemical model based on the concept of water age, able to account for the variable connectivity among soil, groundwater and channels as induced by stream network dynamics. The project will open new avenues to quantify freshwater carbon emissions – crucially dependent on the extent of ephemeral streams – and it will provide a robust basis to identify temporary rivers and maintain their biogeochemical function in times of global change.
These challenging issues aree addressed by developing a novel theoretical framework complemented by extensive field observations within four representative sites along a climatic gradient in the EU: i) the Rietholzbach catchment, in Switzerland; ii) the Valfredda catchment in Northern Italy; iii) the Montecalvello catchment, in Central Italy; iv) the Turbolo catchment in Southern ITaly. Field measurements performed include long-term high-frequency mapping of the active drainage network and daily hydro-chemical data across scales. The experimental dataset will be used to develop and inform a set of innovative modelling tools, including an analytical framework for the description of spatially explicit hydrologic dynamics driven by stochastic rainfall and a modular hydro-chemical model based on the concept of water age, able to account for the variable connectivity among soil, groundwater and channels as induced by stream network dynamics. The project will open new avenues to quantify freshwater carbon emissions – crucially dependent on the extent of ephemeral streams – and it will provide a robust basis to identify temporary rivers and maintain their biogeochemical function in times of global change.
The following major actions have been implemented throughout the project:
Extensive field monitoring has been conducted, with a particular focus on the mapping of river networks and their temporal variability, as well as on the quantification of biogeochemical processes occurring in stream ecosystems. This resulted in the creation of a unique and comprehensive database of hydrological and biogeochemical variables.
Advanced hydrological, biogeochemical, and ecological models have been developed to simulate the spatio-temporal dynamics of river networks, incorporating interactions between hydrology, biogeochemistry, and ecosystem processes.
A comparative assessment of active stream length variations across multiple field sites has been performed, supporting the development of a novel theoretical framework for the interpretation and prediction of active length dynamics in non-perennial river systems.
The influence of microtopographic features on carbon dioxide emissions from riverbeds has been investigated through a combination of theoretical modelling and field observations, highlighting the role of fine-scale topography in controlling gas exchange.
Scaling laws have been formulated for the estimation of the fraction of non-perennial rivers at both regional and global levels, providing a basis for large-scale hydrological assessments in intermittent river systems.
New monitoring strategies have been designed and tested, alongside the development of methodologies for integrating heterogeneous datasets, enabling more robust and transferable data analyses.
The main results achieved over the course of the project include:
Testing and comparing multiple technologies for the mapping of river networks under various field and climatic conditions, including direct visual inspection, water presence sensors, satellite remote sensing, and thermal imaging from UAVs (drones). These comparative analyses enhanced the understanding of the strengths and limitations of each method.
The creation of a unique and high-resolution dataset capturing the temporal dynamics of stream networks across diverse catchments, characterized by varied climatic regimes, geological substrates, and land-use settings.
The development of stochastic models to describe and predict active stream length fluctuations and network reconfigurations, based on Bayesian networks and Directed Acyclic Graphs.
The identification of a universal hierarchical rule governing network expansion and contraction, whereby the most persistent stream segments consistently activate first.
The implementation of dedicated codes and simulation tools for modelling stream network dynamics, ecological interactions, and biogeochemical fluxes.
The proposal of a new methodology for spatial extrapolation of empirical data, allowing for information transfer between sites, gap-filling, and improved spatial representativeness of observations.
The generation of new global and regional estimates of the extent of non-perennial rivers.
The development of novel tools and indicators to assess the hydrological response of river systems to the spatio-temporal dynamics of their networks, supporting improved prediction of flow regimes and associated ecosystem impacts.
Dissemination and outreach:
The scientific results of the project have been widely disseminated through the publication of dozens of articles in international peer-reviewed journals, participation in national and international conferences, the organization of seminars and workshops, and the production of non-scientific outputs, such as popular articles, press releases, and interviews. All scientific outputs are freely available open access and are accessible via the project’s official websites.
Extensive field monitoring has been conducted, with a particular focus on the mapping of river networks and their temporal variability, as well as on the quantification of biogeochemical processes occurring in stream ecosystems. This resulted in the creation of a unique and comprehensive database of hydrological and biogeochemical variables.
Advanced hydrological, biogeochemical, and ecological models have been developed to simulate the spatio-temporal dynamics of river networks, incorporating interactions between hydrology, biogeochemistry, and ecosystem processes.
A comparative assessment of active stream length variations across multiple field sites has been performed, supporting the development of a novel theoretical framework for the interpretation and prediction of active length dynamics in non-perennial river systems.
The influence of microtopographic features on carbon dioxide emissions from riverbeds has been investigated through a combination of theoretical modelling and field observations, highlighting the role of fine-scale topography in controlling gas exchange.
Scaling laws have been formulated for the estimation of the fraction of non-perennial rivers at both regional and global levels, providing a basis for large-scale hydrological assessments in intermittent river systems.
New monitoring strategies have been designed and tested, alongside the development of methodologies for integrating heterogeneous datasets, enabling more robust and transferable data analyses.
The main results achieved over the course of the project include:
Testing and comparing multiple technologies for the mapping of river networks under various field and climatic conditions, including direct visual inspection, water presence sensors, satellite remote sensing, and thermal imaging from UAVs (drones). These comparative analyses enhanced the understanding of the strengths and limitations of each method.
The creation of a unique and high-resolution dataset capturing the temporal dynamics of stream networks across diverse catchments, characterized by varied climatic regimes, geological substrates, and land-use settings.
The development of stochastic models to describe and predict active stream length fluctuations and network reconfigurations, based on Bayesian networks and Directed Acyclic Graphs.
The identification of a universal hierarchical rule governing network expansion and contraction, whereby the most persistent stream segments consistently activate first.
The implementation of dedicated codes and simulation tools for modelling stream network dynamics, ecological interactions, and biogeochemical fluxes.
The proposal of a new methodology for spatial extrapolation of empirical data, allowing for information transfer between sites, gap-filling, and improved spatial representativeness of observations.
The generation of new global and regional estimates of the extent of non-perennial rivers.
The development of novel tools and indicators to assess the hydrological response of river systems to the spatio-temporal dynamics of their networks, supporting improved prediction of flow regimes and associated ecosystem impacts.
Dissemination and outreach:
The scientific results of the project have been widely disseminated through the publication of dozens of articles in international peer-reviewed journals, participation in national and international conferences, the organization of seminars and workshops, and the production of non-scientific outputs, such as popular articles, press releases, and interviews. All scientific outputs are freely available open access and are accessible via the project’s official websites.
The monitoring of the stream network carried out at the DyNET sites has achieved an unprecedented combination of spatial coverage and temporal resolution. For the first time, joint datasets on stream network dynamics and water quality have been collected, paving the way for a deeper understanding of how network variability influences the biogeochemical functioning of riverine systems.
A statistical model has been implemented to link precipitation, evapotranspiration, and stream length dynamics across multiple timescales, offering new insights into the climatic drivers of river intermittency.
One of the key findings of the project is the identification of a universal hierarchical rule in the activation and deactivation of temporary streams: the most persistent segments consistently activate first, regardless of local variability—revealing an underlying order in apparently complex hydrological patterns.
In parallel, physically based models have been developed to simulate stream network expansion and contraction, and their impact on ecological and biogeochemical processes has been analyzed for the first time, highlighting the interdependence between hydrological connectivity and ecosystem functioning.
Finally, the project has produced novel regional and global estimates of the fraction of non-perennial rivers, derived from an integrated approach that combines field observations with model simulations—a significant advancement for large-scale hydrological assessments and climate impact studies.
A statistical model has been implemented to link precipitation, evapotranspiration, and stream length dynamics across multiple timescales, offering new insights into the climatic drivers of river intermittency.
One of the key findings of the project is the identification of a universal hierarchical rule in the activation and deactivation of temporary streams: the most persistent segments consistently activate first, regardless of local variability—revealing an underlying order in apparently complex hydrological patterns.
In parallel, physically based models have been developed to simulate stream network expansion and contraction, and their impact on ecological and biogeochemical processes has been analyzed for the first time, highlighting the interdependence between hydrological connectivity and ecosystem functioning.
Finally, the project has produced novel regional and global estimates of the fraction of non-perennial rivers, derived from an integrated approach that combines field observations with model simulations—a significant advancement for large-scale hydrological assessments and climate impact studies.