The WATZON project

We had financed (small financial support indeed) a PRIN project called WATZON (WATer mixing in the critical ZONe: observations and predictions under environmental changes). It was reborn on the ashes of the Water MIX and PRECISE projects and its short description is:

"Sustainable land and water resources management is inextricably linked to a detailed knowledge of water availability in the critical zone (CZ), which is the thin outer layer of the Earth extending from the top of the tree canopy to the bottom of water aquifers, and that controls water quality and quantity, sustaining human activity. The CZ is experiencing ever-increasing pressure due to growth in human population and water demands, and changing climatic conditions. Understanding, predicting and managing intensification of water use and associated economic services in the CZ, while mitigating and adapting to rapid climate change and biodiversity decline, is now one of the most pressing societal challenges of the 21st century. Vegetation is a fundamental element of the CZ, as connects water from different storages in the subsurface zone with water in the lower atmosphere, therefore regulating water fluxes among different compartments of the CZ. Several studies in the last years have examined water mixing processes in the soil-vegetation-atmosphere system. However, because of the large spatio-temporal variability of subsurface water movement and the capability of plants to access water from both deep and shallow sources, and the resulting highly-complex feedbacks in water exchanges between vegetation and other ecohydrological compartments, fundamental scientific questions on the effect of vegetation on the hydrological cycle, especially under different climatic forcing and land-use conditions, remain unanswered.
The main objective of the project WATZON (WATer mixing in the critical ZONe: observations and predictions under environmental changes) is to advance the understanding of water mixing in the CZ by investigating ecohydrological processes of water exchange between vegetation and surface and subsurface water compartments."

There is a OSF website for the project here.

Specifically, the project aims at:

1. assessing the description of water mixing process across the CZ by using integrated high-resolution isotopic, geophysical and hydrometeorological measurements from point to catchment scale, under different physiographic conditions and climate forcing;
2. testing water exchange mechanisms between subsurface reservoirs and vegetation, and to assess ecohydrological dynamics in different environments by coupling the high-resolution data set from different CZ study sites of the project consortium with advanced ecohydrological models at multiple spatial scales;
3. developing a process-based conceptual framework of ecohydrological processes in the CZ to translate scientific knowledge into evidence to support policy and management decisions concerning water and land use in forested and agricultural ecosystems.

The project objectives will be achieved by integrating different methodological tools, such as environmental tracers (isotopes of hydrogen and oxygen), advanced geophysical measurements and detailed ecohydrological models, to develop an interdisciplinary and holistic comprehension of ecohydrological dynamics under different climatic forcing and land use conditions. 

The project will create a new network of study sites in Italy (Critical Zone study sites) representative for different climatic, physiographic and vegetation conditions in the Mediterranean area, including grassland, forested and agricultural ecosystems. High-resolution and detailed experimental data and observations will be collected in a consistent way across all study sites in order to identify water pools potentially involved in ecohydrological water exchanges and fine-study root water uptake dynamics. The high-quality data collected in the field and the experimental results will serve as a basis to implement and apply new-generation, robust, reliable and realistic ecohydrological models aiming at assessing water mixing and exchange mechanisms between subsurface reservoirs, vegetation and atmosphere at the root-plant scale and the stand and catchment scale. Models will be used also to develop scenario-based projections for assessing the impact of land-use change on ecosystem services under different climatic and environmental conditions. 

In addition to the foreseen significant advancement of scientific research on water mixing processes in the CZ, the other main impact of WATZON will regard the communication with stakeholders and interaction with the civil society. Involvement of the most relevant stakeholders (e.g., water agencies, river basin authorities, reclamation and irrigation districts, government agencies for forest management and protection, national parks, municipalities and regional councils) will allow to translate the acquired scientific knowledge into practices to support effective and sustainable land and water resources management across a variety of climate and physiographic settings.

Our specific efforts, in which I will work with Giacomo Bertoldi (GS) and Giuseppe Formetta will be using the Mastch-Mazia Valley measurements made by EURAC and improve its dataset and, at the same time, lead WP3 of the project: Testing water mixing mechanisms through ecohydrological modelling 

WP3 will use data and experimental results provided by the activities  to test, implement and apply robust, reliable and realistic (R3) ecohydrological models aiming at assessing water mixing and exchange mechanisms between surface, subsurface reservoirs, vegetation and atmosphere within the CROSSes. Particularly, the models will be applied at three main scales: i) the scale of the roots-stems-leaves apparatus, to analyse vegetation water uptake dynamics and their possible switches over time; ii) the stand and iii) catchment scale, to examine how plant water use affects streamflow generation within different ecohydrological regimes. The starting set of models for the project is composed by GEOtop-dv, JGrass-NewAge (JN), now called GEOframe.

Task 3.1.This task will model ecohydrological processes. Soil water flow will be modelled through 3D Richards equation, with improved parameterizations of soil water retention curves, hydraulic conductivity and treatments of hydraulic conductivity. Interaction between water and roots will be implemented. New schemes of plants hydraulics will be implemented to obtain the partition between evaporation and transpiration. Energy and the carbon budget will be modeled to properly constraint the transpiration production. Tools for accounting for water age, and tracers concentration, will be coupled to the new modules of GEOtop and GEOframe. New gridding and numerics will be devised to mimic the experiments and measurements domains.

Task 3.2. This task will couple field data and ecohydrological models at the root-stem-plant volume scale. Along with the 3D simulations, 1D models will be used. Fluxes will be analysed both in time domain and estimating residence and travel time to cope with tracers at integrated soil-plant scale. These results will be compared with those identified by isotope data and geophysical measurements in project's catchments.

Task 3.3. This task will couple field data and ecohydrological models at the stand and catchment scale. New models of plants communities functioning based on plant functional traits and optimality principles will be introduced, along with the more mechanistic ones. The model results will be compared in CRitical zOne Study Sites –(CROSSes) 2, 4, 5 and 6 against isotope data.

WP3 provide the following deliverables.

• Deliverable 3.1: New improved components of the models GEOtop and GEOframe and their documentation at the end of each project’s year (version +1,+2,+3).
• Deliverable 3.2: Case studies will be provided for all the experimental sites, using the various versions of the model components. All the material for the simulation will be provided to the research community online by Open Science Framework.