Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - DyNET (Dynamical river NETworks: climatic controls and biogeochemical function)

Teaser

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...

Summary

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.

Work performed

In the first 18 months of the project, the following major actions have been implemented.
1) Most of the foreseen equipment for the monitoring of chemical and hydrological variables has been purchased and tested. This includes all the YSI sensors for water quality and physical properties of water, the autosamplers, the meteorologic stations, three drones with the related cameras, water presence sensors;
2) In two of the 4 study catchments permanent experimental installations have been set up. Likewise, significant monitoring activities have been carried out in particular for the mapping of the river network and its time variability, as well as the quantification of biogeochemical processes taking place in streams (water quality and carbon dioxide fluxes). In the other two sites, several visual inspections have been undertaken to individuate the field set-up, all the authorizations and permissions have been gathered and a few preliminary experimental installations have been completed;
3) Hydrological and chemical gathered in two staudy catchments data have been analyzed, and preliminary models able to simulate the dynamics of river networks have been developed.

The major results include:
1) testing of technologies for stream network mapping (visual inspection, sensors, satellite images)
2) testing of novel tools to monitor CO2 fluxes from stream to the atmosphere
3) a unique dataset about stream network dynamics in two catchments (weekly resolution for several months of observations)
4) development of preliminary models for stream length and network dynamics

Final results

The monitoring of the stream netwrok performed in the Valfredda catchment during the summer and fall of 2018 reached a combination of size and resolution never reached before. For the first time we do have joint data about water quality and stream netwrok dynamics that opens the avenue to analyze the impcat of dynamical networks on biogeochemical function of rivers. We have developed a newly designed chamber for measuring CO2 fluxes from strema to the atmosphere that minimizes the turbulence induced on the water flows. We have developed a statistical model that relates precipitation and stream lenght across different timescales.

The project plans to expand the dataset and include a detailed characterization of stream network dynamics in the four study sites, so as to unravel the role of climatic conditions of river form and function. the project also plans to develop physically based models for stream netwrok expansion and contraction, and analyze the impact of these dynamics on carbon cycling in catchments, through the use of biogeochemical models and water quality data.

Website & more info

More info: http://www.erc-dynet.it.