Riccardo Rigon

As observed in the last years, flood and drought events are getting more likely to happen due to climate change and can cause significant environmental, social and economic damages.For this reason, already in 2021, the Po River District Authority (AdbPo) undertook the implementation of the GEOframe modelling system on the whole territory of the district in accordance with the GCU-M (Gruppo di Coordinamento Unificato-Magre) to update the existing numerical modelling for water resource management and with the objective of producing a better quantification and forecast of the spatial and temporal water availability across the entire river basin and, finally, to improve the planning activity of theAuthority.The GEOframe system was developed by a scientific international community, led by the University of Trento, and is a semi-distributed conceptual model, with high modularity and flexibility, completely open-source.The implementation of GEOframe in the Po River District has begun in the Valle d’Aosta Region, the most upstream part of the district.After an initial part of meteorological data collection, validation, spatial interpolation, and geomorphological analysis, a first running of the model to assess all the components of the hydrological balance (evapotranspiration, snow accumulation, water storage and discharge) was carried out.Consequently, the calibration phase started, consisting of the research of the values of the characteristic parameters of the model which fit the discharge evolution recorded in the hydrometers of the region in the best possible way, comparing the modelled discharge trend with the measured one.The calibration, based on KGE method, has been executed in 10 hydrometers in Valle d’Aosta across a 4 years period. The results were encouraging, with an objective function of 0.76 at the closure point of the region.The same process is now in progress in Piemonte, one of the biggest regions of Italy, which contains more than 100 hydrometers. The resulting objective functions are in general rather high and will be presented in this work.At the same time, thanks to the geomorphological analysis, most part of Po River District (up to Pontelagoscuro (FE)), which totally occupies more than 42,000 km2, has been divided into subbasins, the hydrological reference units where the simulation process takes place, and this dataset will be open-source and shared with the scientific community.On the other hand, the interpolation and spatialization of the meteorological data will be carried out according to the 1 km2 European Environmental Agency reference grid.In conclusion, in this initial stage of implementation of the model and calibration of its parameters, it was possible to assess the capacity of GEOframe to simulate not only the water discharge but also the other components of the water cycle, namely the evapotranspiration, the water storage and the snow accumulation. Furtheremore, implementing GEOframe in a mountainous area underlines the importance and the influence that snow and glaciers, especially in a higher temperature scenario due to climate change, can have on water availability and, therefore, a better modelling component of these elements will be implemented in the future developments of GEOframe.

<p>Snow water equivalent is a key variable in hydrology. An accurate SWE estimation is crucial for runoff prediction, especially for catchments with strong nival regimes. Direct observations are unfortunately rare and are available only at a point scale. Accurate spatialized estimates of SWE are thus difficult to be obtained. Physically based models often suffer from the inaccuracies of input data and uncertainty of model parametrization. In this sense, the integration of traditional techniques with remote sensing observation is valuable. Although current satellite missions do not provide direct SWE observation, they allow us to extract important proxy information that is crucial for SWE reconstruction. In this sense, we propose to exploit optical and radar sensors to retrieve accurate information on the persistence of snow on the ground. In fact, the longer the persistence, the deeper the snowpack. To achieve enough spatial and temporal detail, we merged multi-scale information from MODIS, Sentinel-2, and Landsat missions. The key idea is to exploit the snow pattern persistence that we can observe with good spatial detail from Landsat and Sentinel-2 missions to reconstruct the scene when a low-resolution image (MODIS) is acquired. Furthermore, information on the duration of the melting phase can also be retrieved by exploiting the synthetic aperture radar (SAR) mounted on board of Sentinel-1. Hence, we can estimate the number of days of melting. In-situ data, when available, are also exploited in the reconstruction. In detail, air temperature is used to estimate the potential melting and the snow depth increases to determine the number of days in accumulation. The reconstruction approach is then simple: by knowing the days in melting, the total amount of melted SWE is determined. Assuming that the melted SWE is equal to the accumulated SWE, we can redistribute SWE throughout the season using a simple approach as the degree day. The final output is a daily time-series with a spatial resolution of few dozens of m. One of the major advantage of the proposed approach, compared to more traditional SWE estimation techniques, is that it does not depend from precipitation observation, often highly uncertain in high-elevation catchments. When evaluated against a reference product (i.e., Airborne Snow Observatory), the method shows a bias of -22 mm and an RMSE of 212 mm for a catchment of 970 km2 in Sierra Nevada (CA). In this work, we investigate the relationship between the melted SWE and the measured riverine discharge for a number of catchments in South Tyrol (Italy). The results may be of great interest, especially for poorly monitored basins with highly variable snow accumulation that are exploited for hydroelectric energy production. In detail, we propose a long-term analysis on SWE time-series to understand if there are evident trends that might improve hydroelectric power management.  </p>

Hack\u27s law is reviewed, emphasizing its implications for the elongation of river basins as well as its connections with their fractal characteristics. The relation between Hack\u27s law and the internal structure of river basins is investigated experimentally through digital elevation models. It is found that Hack\u27s exponent, elongation, and some relevant fractal characters are closely related. The self-affine character of basin boundaries is shown to be connected to the power law decay of the probability of total contributing areas at any link and to Hack\u27s law. An explanation for Hack\u27s law is derived from scaling arguments. From the results we suggest that a statistical framework referring to the scaling invariance of the entire basin structure should be used in the interpretation of Hack\u27s law

The paper presents the integration of the GEOtop model into the Object Modeling Sys- tem version 3.0 (OMS3) and its application. GEOtop is a physically based spatially distributed rainfall-runoff model, performing water and energy budgets. The OMS3 integration widened the application range of GEOtop as presented in the paper. By running GEOtop as an OMS3 model component it can interact with the GIS uDig-JGrass to utilize other geo-processing, visualization, and modeling components. Furthermore, OMS3 components for automatic calibration, sensitivity analysis, or meteorological interpolation can now interact with GEOtop. Finally, a case study of the model application is presented. Results in terms of soil water content and suction are compared with measured data. Model performance is evaluated by computing traditional goodness of fit indi- ces such as Nash Sutcliffe and percent bias.

The EPA Storm Water Management Model (SWMM) is a robust software, widely used in urban catchments. However, it lacks two important aspects: a module for Storm Water Drainage System (SWDS) design and a flexible model structure. JSWMM, a new SWMM-based Java software, is developed to overcome these constraints. The SWMM data structure is refactored following the object oriented paradigm, while the computational core is split and redesigned as OMS3-compliant components. This approach allows for easily modifying and extending available modules by adding new functionalities, e.g. infiltration as part of runoff computation, different equation to evaluate evapotranspiration, etc. Input and output of JSWMM are maintained fully compatible with those of SWMM with which it remains, therefore, interoperable. The SWDS design module is based on the Geomorphological Instantaneous Unit Hydrograph theory by Rodríguez-Iturbe et al. (1979) and by Rigon et al. (2016). It automates the process of pipe di...

In hydrological modeling snowmelt is computed along two different approaches: the physically based one simulates the snowpack evolution in terms of accumulation and ablation by means of solution of the energy balance equation; the second, simpler approach, uses instead the meteorological variables as indices of physical processes. The simplified models are limited to forecasting only the snow water equivalent (SWE, the mass of liquid water in the snowpack) and not other variables.

The theory of travel time and residence time distributions is reworked from the point of view of the hydrological storages and fluxes involved. The forward and backward travel time distri- bution functions are defined in terms of conditional probabilities. We explain Niemi's formula and show how it can be interpreted as an expression of the Bayes theorem. Some connections between this theory and population theory are identified by introducing an expression which connects life expectancy with travel times. The theory can be applied to conservative solutes, including a method of estimating the storage selection functions. An example, based on the Nash hydrograph, illustrates some key aspects of the theory.

Abstract. Hack's law is reviewed, emphasizing its implications for the elongation of river basins as well as its connections with their fractal characteristics. The relation between Hack's law and the internal structure of river basins is investigated experimentally through digital elevation models. It is found that Hack's exponent, elongation, and some relevant fractal characters are closely related. The self-affine character of basin boundaries is shown to be connected to the power law decay of the probability of total contributing areas at any ...

Evapotranspiration (ET) is a key variable in the hydrological cycle and it directly impacts the surface balance and its accurate assessment is essential for a correct water management. ET is difficult to measure, since the existing methods for its direct estimate, such as the weighing lysimeter or the eddy-covariance system, are often expensive and require well-trained research personnel. To overcome this limit, different authors developed experimental models for indirect estimation of ET. However, since the accuracy of ET prediction is crucial from different points of view, the continuous search for more and more precise modeling approaches is encouraged. In light of this, the aim of the present work is to test the efficiency in predicting ET fluxes in a newly introduced physical-based model, named Prospero, which is based on the ability to compute the ET using a multi-layer canopy model, solving the energy balance both for the sunlight and shadow vegetation, extending the recently...

Evapotranspiration (ET) is a key variable in the hydrological cycle and it directly impacts the surface balance and its accurate assessment is essential for a correct water management. ET is difficult to measure, since the existing methods for its direct estimate, such as the weighing lysimeter or the eddy-covariance system, are often expensive and require well-trained research personnel. To overcome this limit, different authors developed experimental models for indirect estimation of ET. However, since the accuracy of ET prediction is crucial from different points of view, the continuous search for more and more precise modeling approaches is encouraged. In light of this, the aim of the present work is to test the efficiency in predicting ET fluxes in a newly introduced physical-based model, named Prospero, which is based on the ability to compute the ET using a multi-layer canopy model, solving the energy balance both for the sunlight and shadow vegetation, extending the recently...

NewAge-JGrass is a semi-distributed hydrological modelling system. It is based on the object-oriented modelling framework (OMS version 3), on the JGrasstools and on the Geotools. To make it more effective, it is interoperable with many other tools such as R-project, gvSIG GIS, GitHub and other collaborative sharing tools, such as Authorea. OMS3 allows to create science simulation components, which are implemented with a standard, well-defined purpose and interface. The encapsulation of the source code in components make them easier to be inspected and its copyleft license allows the easy access to the code, its use and its improvement. The components can be connected to obtain a variety of modelling solutions, i.e. a connection of components that perform a modelling task, following an “out-to-in” scheme. According to the OMS3 standards, each NewAge-JGrass component was developed to simulate a specific hydrological process. After the geomorphological analysis of the watershed, it is ...

Here a snow accumulation and melt module implemented in the GEOTOP model is presented and tested. GEOTOP is a distributed model of the hydrological cycle, based on digital elevation models (DEMs), which calculates the discharge at the basin outlet and estimates the local and distributed values of several hydro-meteorological quantities. It solves the energy and the mass balance jointly and deals accurately with the effects of topography on the interactions among radiation physics, energy balance and hydrological cycle. Soil properties are considered to depend on soil temperature and moisture and the heat, and water transfer in the soil is modeled using a multi-layer approach. The snow module solves for the soil–snow energy and mass exchanges, and, together with a runoff production module, is embedded in a more general energy balance model that provides all the boundary conditions required. The snowpack is schematized as a single snow layer where a limited number of physical processe...

Hack's law is reviewed, emphasizing its implications for the elongation of river basins as well as its connections with their fractal characteristics. The relation between Hack's law and the internal structure of river basins is investigated experimentally through digital elevation models. It is found that Hack's exponent, elongation, and some relevant fractal characters are closely related. The self-affine character of basin boundaries is shown to be connected to the power law decay of the probability of total contributing areas at any link and to Hack's law. An explanation for Hack's law is derived from scaling arguments. From the results we suggest that a statistical framework referring to the scaling invariance of the entire basin structure should be used in the interpretation of Hack's law.

The Upper Blue Nile basin is one of the most data-scarce regions in developing countries, hence, the hydrological information required for informed decision making in water resources management is limited. The hydrological complexity of the basin, tied with the lack of hydrometerological data, means that most hydrological studies in the region are either restricted to small subbasins where there are relatively better hydrometeorological data available, or at the whole basin scale but at very coarse time scales and spatial resolutions. In this study we develop a methodology that can improve the state-of-art by 5 using the available, but sparse, hydrometerological data and satellite products to obtain the estimates of all the components of the hydrological cycle (precipitation, evapotranspiration, discharge, and storage). To obtain the water budget closure, we use the JGrass-NewAge system and various remote sensing products. The satellite products SM2R-CCI is used for obtaining the ra...

The modelling of natural phenomena to solve a wide range of problems has increased in popularity in the last three decades. However, as the size and complexity of the source code of environmental models has grown, issues related to maintainability and further development have arisen. In this work, we show an innovative way to simplify the reuse and development of new models, decoupling the physics of the processes from the schematization of information flow and feedback. Each physical process (for instance, evapotranspiration or runoff production) might be implemented as a stand alone component for a framework like OMS v3, which encapsulates the computation of the problem and can be connected with other components to realize a modelling solution. The information flow among the physical parts of the control volume might be represented as a network or a simple tree, which is implemented as a data structure inside the OMS v3 framework as well. The structure of the network allows for si...

This paper describes the structure of JGrass-NewAge: a system for hydrological forecasting and management at the basin scale. It is based on the Geographic Information System uDig and composed of two parts: (i) the system for data and result visualization based on JGrass and (ii) the modelling components. The latter are implemented as OMS3 components, which can be connected or excluded at runtime, according to the needs of who runs the model, and work seamlessly inside the uDig ver.1.3.1 spatial toolbox. Compared to other models which are built upon monolithic code, JGrass-NewAge allows for having multiple modelling solutions for the same process, provided they share the same input and outputs. Since sound hydrological modelling requires a proper definition of a digital watershed model, this paper presents and discusses an implementation based on uDig .

We thank the reviewer for her/his observations, which helped us improve our manuscript. This response tries to use the practice of the interactive discussion, and does not yet produce a new manuscript, which will be submitted after the closure of the review phase, upon request of the Editor. We introduce here, however, the main adjustments that we will make in the final version of the revised paper based upon the reviewer’s suggestions.

Rainfall induced shallow landslides cause significant damages involving loss of life and properties. Predict shallow landslides susceptible locations is a complex task that involves many disciplines: hydrology, geotechnical science, geomorphology, statistics. Usually to accomplish this task two main approaches are used: statistical or physically based model. In this paper three physically based models for landslides susceptibility analysis were integrated in the Object Modelling System (OMS) and tested in real world applications. Models presented have an increasing degree of complexity. Effects of three different hydrological components connected to the stability model and of model parameters optimization were investigated. Their integration in OMS allows the use of other components such as GIS tools to manage inputsoutput processes, and automatic calibration algorithms to estimate model parameters. Finally, model performances were quantified by using traditional goodness of fit ind...

It is known that measuring and modeling of water and solute fluxes across soil-plant-atmosphere is nowadays a very important challenge because of the complexity of both soil and plants. In particular evapotranspiration (Schymanski and Or, 2017) is related with radiation, temperature, relative humidity, wind but it depends also by the water content in soil. Specifically, the water content varies with precipitation and with the water properties of soil, soil water retention curves and soil hydraulic conductivity. To consider the effects of water content on the rate of evapotranspiration it is necessary to study infiltration and evapotranspiration processes and find a physical, but also, a modelling point of view to coupled these processes.

Incoming (Rli) and outgoing (Rlo) longwave atmospheric radiation are very important components of the global radiation balance. They influence many hydrological processes such as evapotranspiration, soil-surface temperature, energy balance, and snowmelt. Field measures of Rli and Rlo are extremely rare except for a few sites and experimental watersheds. Many parameterization schemes were proposed in order to model Rli and Rlo by using easily available meteorological observations such as air temperature, relative humidity, incoming solar radiation and cloud cover. In this work 10 methods of parameterizing clear sky radiation for the estimation of Rli and Rlo were integrated in the GIS based hydrological system NewAge-JGrass and tested against field measurement data at hourly and daily timesteps. Two applications were performed. In the first application the 11 algorithms were applied by using the model parameters as proposed in literature. In the second application we preserved the an...

Many assumptions are usually made when dealing with forecasting landslide triggering; those assumptions mainly focus on steady-state hydrology and uniform soil properties and soil depth. The presented work is an effort toward removing these assumptions to better reproduce the physics of the triggering. The hydrology is reproduced through an improved version of the GEOtop model, which runs on a 3-dimensional grid built on a detailed topography and describes the temporal and spatial evolution of the water table, of the soil moisture content and of the matric suction. It also simulates the transient pore water pressure due to infiltration and redistribution processes, which is of primary importance in landslide triggering. The stability analysis incorporates the dynamic description of soil moisture and tackles the heterogeneity of soil mechanical properties through a probabilistic approach which describes soil parameters as random variables. This approach not only maps the failure prob...

The differences in the conceptual and practical implementation of two type of models will be enlighten. The different conceptualization of the same processes and their rational is discussed also in comparison with other analogous "standard" models. Furthermore, new mathematical and numerical methods are envisioned to include subgrid variability directly in the mathematics of the models, and an example based on subsurface-surface water interaction will be presented. Finally, aspects connected to the characterization of the models at different scales is discussed, in the attempt to frame the meaning of Galileian experiments in such a context.

We present, by using previous results on extended Petri Nets, the relations of various hydrological dynamical systems ($\mathtt{HDSys}$) derived from the water budget ($\mathtt{DynWB}$). Once $\mathtt{DynWB}$ has been implemented, there exist a consistent way to get the equations for backward travel time distributions ($\mathtt{DynTT}$), for the forward response time distribution ($\mathtt{DynRTD}$) and for the concentration for a solute or a tracer ($\mathtt{DynC}$). We show that the $\mathtt{DynWB}$ has a correspondence one to many with the $\mathtt{DynTT}$. In fact to any one of the $\mathtt{DynWB}$ equation correspond as many equation as the input precipitation events times. The $\mathtt{DynTT}$ is related to $\mathtt{DynRTD}$ by the Niemi’s relationship and, in presence of multiple, $n$ outputs, by the specification of $n-1$ partition functions, which determine which fraction of water volume, injected in the control volume at a specific time $t_{in}$, goes asymptotically into a specific output. The $\mathtt{DynC}$, given $\mathtt{DynTT}$, depends further on the solute/tracer concentration in inputs. The paper clarifies the complicate set of relations above by using an example from literature. Upon the introduction of the appropriate information, it is also shown how these ($\mathtt{HDSys}$) can be solved simultaneously without duplicating calculations. It is also shown that these systems can be solved exactly, under the hypothesis of uniform mixing of water ages inside each reservoir within the system.

In this work, the semi-distributed hydrological modeling system GEOframe-NewAge was integrated with a web-based decision support system implemented for the Civil Protection Agency of the Basilicata region, Italy. The aim of this research was to forecast in near real-time the most important hydrological variables at 160 control points distributed over the entire region. The major challenge was to make the system operational in a data-scarce region characterized by a high hydraulic complexity, with several dams and infrastructures. In fact, only six streamflow gauges were available for the calibration of the model parameters. Reliable parameter sets were obtained by simulating the hydrological budget and then calibrating the rainfall-runoff parameters. After the extraction of the flow-rating curves, six sets of parameters were obtained considering the different streamflow components (i.e., the baseflow and surface runoff) and using a multi-site calibration approach. The results show a...

In this work, the semi-distributed hydrological modeling system GEOframe-NewAge was integrated with a web-based decision support system implemented for the Civil Protection Agency of the Basilicata region, Italy. The aim of this research was to forecast in near real-time the most important hydrological variables at 160 control points distributed over the entire region. The major challenge was to make the system operational in a data-scarce region characterized by a high hydraulic complexity, with several dams and infrastructures. In fact, only six streamflow gauges were available for the calibration of the model parameters. Reliable parameter sets were obtained by simulating the hydrological budget and then calibrating the rainfall-runoff parameters. After the extraction of the flow-rating curves, six sets of parameters were obtained considering the different streamflow components (i.e., the baseflow and surface runoff) and using a multi-site calibration approach. The results show a...