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Urban green infrastructures are considered useful tools to mitigate air pollution, increase the resistance of cities to climate change, optimize energy consumption expenses and promote the integral management of economic, social and cultural development, according to a "sustainable cooperation". However, there are few studies that quantitatively support this contribution and there is also a lack of knowledge about which species are the most suitable for an urban area in order to improve air quality. Therefore, the research project proposes to analyze the improvement of air quality and the contribution to reducing the effects of climate change by trees of an entire urban area. i-Tree Eco software and the inventory of the urban trees of the Madrid Municipality of Boadilla del Monte, with which the project has been developed, have been used. Results about air pollutants reduction have been compared with the Municipality's emissions in order to see how urban greenery helps to the improvement of air quality. Finally, an annual monetary estimation of the Ecosystem Services (ES) offered by the urban trees of the city has been made through the software, then compared with the annual costs (planting, maintenance, removal) agreed with the Municipality of Boadilla, reaching a Cost-Benefit Analysis representative of the contribution given by urban green areas to the surroundings.

The population growth and its concentration within cities, on the one hand lead to an increment of water demand and on the other hand affect the urban water cycle with frequent urban flood events associated to rain extreme events. New approaches to the water management are currently being developed where a role is assigned to rain water harvesting (RWH). RWH provides water for non-potable uses (private and public, indoor and outdoor), reducing water consumption. Moreover, RWH allows to partially retain water on site, reducing the probability of failures of the sewerage system during heavy rain events.These positive effects are easily evaluable at a building scale when well-known behavioral models are used, while the evaluation becomes often more complex at an urban scale, due to the lack of characteristics and demographic data about all the buildings in the city. In our work, we consider RWH impact at the urban scale, by means of the representative building concept.We focus on several hypothetical retrofitting scenarios for the residential buildings of Turin (Italy): 1) domestic use of rainwater (e.g., toilet flushing and the washing machine), where buildings are independent of each other, and 2) two public uses of rainwater (the irrigation of public green areas and street washing), for which we have hypothesized that the rainwater collection takes place at a district scale. We estimate a reduction of 42% in the non-potable water consumption for domestic use (values vary across the municipal districts from 29% to 62%, according to the characteristics of the buildings), while for irrigation and street washing, that require a lower amount of water, about 80% of the water can be provided by RWH. The highest reduction of the flow peak conveyed to the sewerage system during extreme storms is reached in the domestic use scenario (about 60%, quite constant across the city), while for public uses the retention capacity is very low.Finally, our estimations based on historical rainfall series are examined against different climate change scenarios.

The concept of ecosystem services (ES), as a set of components of the natural capital that provide products and services directed to humans, was born around the middle of the last century, reaching a more systematic definition in the early 2000s with the Millennium Ecosystem Assessment (MA, 2005). This issue is implicitly linked to popular research topics, such as climate change, population well-being, fight against hunger in the world and has undergone a significant increasing interest from scientific research since the SDGs subscription, defined in the 2030 Agenda.With the thrust of the investigation into this new branch, various tools have been created aimed at dealing with ecosystem services, not only from a qualitative point of view but in quantitative terms. The present work aims to analyze the applicability of a specific SE quantification software for vegetation, based both on the use of meteorological data and on the acquisition of field data and capable of returning outputs relating to the main components: environment (air quality), soil (use and cover) and water (quality and quantity of water runoff, with a focus on vegetation hydrology). The combination of this eco-hydrological model with a monetary ES evaluation is also interesting: although the economic model considered is particularly simple and therefore characterized by a non-negligible standard error, it is important to underline the direct and spontaneous association between SE and monetary quantification considered by the software, unlike how at the end of the last century the economic value of nature was still neglected.Finally, the main results of a ES quantification project in an Italian urban context will be discussed, underlining the environmental improvement to the surroundings and the social benefits for the population.

In recent years, safeguarding approaches and environmental management initiatives have been adopted both by international institutions and local governments , aimed at sustainable use of natural resources and their restoration, in order to manage hazard level of climate change consequences (urban flooding, droughts and water shortages, sea level rise, issues with food security).Cities represent the main collectors of these effects, consequently they need to implement specific adaptation plans mitigating consequences of such future events: Green Infrastructures (G.I.) fall within the most effective tools for achieving the goal. In the urban context, they also identify themselves as valid strategies for biodiversity recovery and ecological functions.This work analyzes the role of a G.I. in an urban environment, with the aim of quantifying Ecosystem Services (E.S.) provided by vegetation: through usage of i-Tree, specific software suite for E.S. quantification, the sustainability offered by “Le Vallere” park, a 34-hectares greenspace spread between municipalities of Turin and Moncalieri (Italy), was analyzed, in collaboration with the related management institution (Ente di gestione delle Aree Protette del Po torinese). The study, carried out using two specific tools (i-Tree Eco and i-Tree Hydro), focuses on different aspects: carbon sequestration and storage, atmospheric pollutants reduction, avoided water runoff and water quality improvement are just some of the environmental benefits generated by tree population. Tools enable to carry out the analysis also from an economic point of view, evaluating monetary benefits brought by the green infrastructure both at present day and in the future, taking into account climate change effects through projections based on the regional climatic model COSMO-CLM (RCP 4.5 and RCP 8.5 scenarios).The work led to deepen potential held by the greenspace, helping the cooperating management institution to plan future territorial agenda and to find innovative approaches for an integrated and sustainable hazard control.

This paper is part of the panorama of studies on climate changes in an urban context. Starting from the concept of Ecosystem Services, we aim to underline the importance of rebalancing equally what is demanded in an urban ecosystem and what it provides people with, focusing on pollutants quantity, carbon sequestration and runoff reduction. Ecosystem services (ES) can be defined as the components of natural capital that provide direct products (food, drinking water, etc) and benefits (like biological variability and soil creation) to people. Our goal is to determinate and to quantify ES related to urban greenspaces in terms of both economic and environmental point of view.Specifically, the study has been developed through the use of i-Tree, a suite developed in the US context, that shows on both small and large scale the economic, environmental and water-related benefits provided by a green area. Its applicability has been tested for an Italian context on a newly built park, located in “Revello Street – Turin”, with the collaboration of the Municipality of Turin, comparing past, present and future scenarios.Eco, Hydro and Canopy tools were used for that urban greenspace, providing useful information on software usage and justifying the creation and/or the expansion of new urban green areas through economic and environmental outputs. Results show how the transition from a past residential area to an almost totally green area has led to air quality improvement, with a consequent increase in carbon storage and pollutants reduction, while in view of future improvement works in the park (intensification of arboreal and shrubby presence), the results economically justify the intervention by showing a significant water runoff reduction with consequent reduction of flood events risk.This work aims to deepen advantages and disadvantages of i-Tree and to insert the software as an effective and innovative tool, not widely known in a European context, for the monitoring and development of methodologies to make urban spaces increasingly sustainable, within a view of smart cities.

Urban runoff negatively impacts the receiving streams and different solutions have been proposed in literature to limit the effect of urbanization on the water balance. These solutions suggest to manage urban runoff in order to switch from a post-development river hydrograph (high peak and short duration) back again to a pre-development hydrograph (low peak and high duration). Combined sewer overflows (CSOs) represent severe pollutant sources for receiving streams due to the combination of first flush of roads and sewers and black water conveyed by combined sewer systems. Constructed wetlands for CSO treatment (CSO-CWs) are adopted with increasing frequency for reducing pollutant inputs to streams. Moreover, these systems exhibit the characteristic to behave similarly to ponds, wetlands, and bioretention systems that provide flood mitigation by decreasing the intensity of peak flows. This work aims to show the additional ecosystem service provided by CSO-CWs in term of limitation of the hydraulic impact of CSO on stream hydrograph. A mathematical model is developed to simulate the hydraulic behavior of a real case study situated in Gorla Maggiore (Italy), which includes vertical flow subsurface beds (VF) as first stage and a free water surface bed (FWS) as second stage. The model simulates the unsaturated flow within VF and the accumulation of water on the top of VF and within FWS. Results show a satisfactory lamination performance of the system for both single and up to 5 consecutive flood events, with a peak flow reduction ranging from 52.7% to 95.4%. Withdrawn of flow rate from the river in order to cope with long dry period does not significantly affect the lamination performances. The considered CSO-CW exhibits an excellent lamination efficiency also during more intense floods events, with a peak flow reduction of 86.2% for a CSO event with return period of 10 years. The flow rate frequency density function determined by the CSO-CW is more shifted towards lower values compared to untreated CSOs. These results indicate that CSO-CWs work properly in terms of reduction of CSO urbanization impact on stream hydrology.

Increasing urbanization, landscape conversion, and resource consumption represent the most important, visible and irreversible human-induced actions on Earth. As a consequence, nowadays it is of seminal importance to understand and assess how anthropic pressures are related to the provision of ecosystem services (ES). This paper focuses on urban parks and their provision of water-induced ecosystem services (WES) connected to urban hydrologic cycle. The study uses a broad holistic approach to comprehensively understand the links between anthropic pressures and WES production. With the help of biological, chemical, and physical indicators collected in publicly available databases a scoring matrix was created. The method was applied to two different parks in Turin (Italy), the Arrivore Park and the Michelotti Park. The matrices reveal that anthropic pressures are marked, and the most affected WES are habitat maintenance, recreational services, and the provision of drinkable and non-drinkable water. The hydromorphological alterations are the anthropogenic pressures most strongly present in both parks. More specifically, in the Arrivore Park urbanization represents one of the most important pressures while the main pressures in the Michelotti Park are water abstraction for industrial and agricultural use and point source pollution. This study makes a major contribution to research on WES assessment by demonstrating the possibility to understand and to assess the impact of anthropic pressures. Moreover, the proposed matrix method provides an easy tool to support policymakers, public administrations, and private companies within sustainable urban planning.

Overshot water wheels are hydropower converters generally employed for head differences up to 6 m and maximum flow rates of 150−200 L/s per meter width. The maximum hydraulic efficiency (8...

Breastshot water wheels are gravity hydraulic machines employed in low head sites. The scope of this work is to test the performance of a breastshot water wheel with two geometric inflow configurations: a sluice gate at different openings and two vertical overflow weirs. With the sluice gate, the maximum efficiency of the plant is 75%, constant over a wide range of flow rates, while the efficiency with the weir is increasing in the same flow rate range. Therefore, the wheel with the weir can exploit higher water volumes, and also it performs better at high power input. In practical applications, the inflow configuration can be effectively controlled to optimize the operative working conditions of breastshot water wheels, depending on the external hydraulic ones. The experimental results are also discussed in dimensionless terms, in order to support engineers in the design of similar breastshot water wheels.

Water wheels can be efficient hydropower converters at low heads and low discharges. The paper presents the results of a study of a breastshot water wheel in a laboratory experimental channel. The obtained data show that breastshot water wheels can reach a maximum efficiency of about 75%, at a rotational velocity which is about 60% of the runaway velocity. The maximum efficiency is constant over a wide range of flow rates. A dimensional analysis is then carried out and a simple relationship for estimating the maximum mechanical power output of geometrically similar wheels is determined, relating the Newton number (dimensionless maximum power output) to the Reynolds number (function of the hydraulic conditions and channel geometry).

A rotary hydrostatic pressure machine (RHPM) is a hydropower converter for very low head applications (less than 2.5 m). An RHPM can be installed in straight canals, because its wheel can g...

For hundreds of years, millstones, hammers, sawmills, spinning mills have been powered by water wheels. Recently, there is a renewed interest in their use, both for their widespread diffusion in the territory, and for the excellent environmental integration. In the paper, the mechanical architecture of an old water mill, from water wheels to millstones, is described and the functional details of various mechanisms are provided.

Thanks to a new sensibility to renewable energy and to local and smart electricity production, traditional water wheels are regarded again as a clean and accessible way for pico-micro hydro electricity generation, especially in presence of very low heads and small flowrates. In particular, among the different kinds of water wheels, the overshot ones exploit the lowest flowrates with the highest efficiency (efficiency up to 85–90%). Therefore, in order to determine the performance characteristics and to estimate the power losses and the output power for overshot water wheels, theoretical and experimental analyses are here developed. By a numerical optimization process, the power losses and the mechanical output power are theoretically quantified. A critical angular velocity is also identified (about 65% of the runaway speed). When the wheel rotation speed approaches the critical velocity, volumetric losses at the top of the wheel begin to increase linearly with the rotational velocity, while the other power losses start to decrease, due to the lower amount of water available to the wheel.

Breastshot water wheels were in widespread use in the Nineteenth and Early Twentieth century for the production of energy; although they represent an economic, efficient and sustainable technology, only a small amount of research has been paid to water wheels nowadays, in particular to the breastshot ones. In this work a theoretical approach is adopted to estimate the different kinds of power losses occurring inside a breastshot water wheel, in order to predict its mechanical output power. The theoretical results are then validated with experimental results on a physical steel model. The characteristics experimental curves of the wheel are also illustrated, reporting the wheel efficiency and output power versus the flowrate, stream and wheel velocity. The average estimated error between the experimental and the estimated theoretical output power is 9%, which is much lower than that calculated using some past formulations found in literature. The theoretical results show that the big power losses are the dissipation of the stream kinetic energy against the blades and the hydraulic losses in the headrace, after the passage through the sluice gate; therefore, a better design of the inlet and blades geometry may improve the efficiency of the wheel.

At low head sites and at low discharges, water wheels can be considered among the most convenient hydropower converters to install. The aim of this work is to improve the performance of an existing breastshot water wheel by changing the blade shape using computational fluid dynamic (CFD) simulations. Three optimal profiles are investigated: the profile of the existing blades, a circular profile and an elliptical profile. The results are validated by performing experimental tests on the wheel with the existing profile. The numerical results show that the efficiency of breastshot wheels is affected by the blade profile. The average increase in efficiency using the new circular profile is about 4 % with respect to the profile of the existing blades.

Urban green spaces have been recognized as an important source of ecosystem services, whose quantification requires the determination of quantities related to energy, water, carbon and soil nutrient content. In this paper we propose a stochastic ecohydrological model that couples two existing models for water and nutrients in urban soil at the single street-tree scale. The model input are rainfall and irrigation, for water, and deposition and fertilization, for nitrogen, while the output are evapotranspiration, runoff and deep percolation, for water, and plant uptake and leaching, for nitrogen. The various terms are related to the amount of paved and impervious surfaces that surround the tree trunk and regulate the water and nutrient fluxes in and out the soil. Particular attention is paid to the effects of seasonal variations on plant water and nutrients through a temporal variation of the hydrologic variables (i.e., temperature and rainfall intensity and frequencies). The average model outputs are preliminarily compared with the scant existing literature data, supporting the model application to cities with different climatic conditions. The model results are used to estimate the potential for ecosystem services like tree cooling effects, soil carbon sequestration or storm-water management. Because of the minimal structure of the proposed model, it requires a very low amount of data, while accounting for the stochastic input of rainfall. In the context of climate change and increasing urbanization, the model may offer useful indications to urban planners to enhance ecosystem services while minimizing irrigation, fertilization and their related costs.

International audience; The average organic and hydraulic loads that Constructed Wetlands (CWs) receive are key parameters for their adequate long-term functioning. However, over their lifespan they will inevitably be subject to either episodic or sustained overloadings. Despite that the consequences of sustained overloading are well known (e.g., clogging), the threshold of overloads that these systems can tolerate is difficult to determine. Moreover, the mechanisms that might sustain the buffering capacity (i.e., the reduction of peaks in nutrient load) during overloads are not well understood. The aim of this work is to evaluate the effect of sudden but sustained organic and hydraulic overloads on the general functioning of CWs. To that end, the mathematical model BIO_PORE was used to simulate five different scenarios, based on the features and operation conditions of a pilot CW system: a control simulation representing the average loads; 2 simulations representing +10% and +30% sustained organic overloads; one simulation representing a sustained +30% hydraulic overload; and one simulation with sustained organic and hydraulic overloads of +15% each. Different model outputs (e.g., total bacterial biomass and its spatial distribution, effluent concentrations) were compared among different simulations to evaluate the effects of such operation changes. Results reveal that overloads determine a temporary decrease in removal efficiency before microbial biomass adapts to the new conditions and COD removal efficiency is recovered. Increasing organic overloads cause stronger temporary decreases in COD removal efficiency compared to increasing hydraulic loads. The pace at which clogging develops increases by 10% for each 10% increase on the organic load.

To assess spring vulnerability level, the vulnerability estimator for spring protection areas (VESPA) index has been proposed. The VESPA index method is based on the joint use of discharge, electrical conductivity, and temperature data, measured at the spring location. In this paper the VESPA index method has been examined through the analysis of observed time series with respect to the following aspects: (1) the time extension of the data set, (2) the use of averaged data, and (3) the number of missing data. For this purpose four springs fed by different geological systems were considered. The outcomes of the statistical analysis show that the VESPA index is a reliable way to identify higher vulnerability levels while some uncertainty occurs in the identification of low and medium vulnerability levels.

Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed.

Although horizontal flow constructed wetlands (HF CWs) are usually subjected to unsteady loads in real application, the modelling of HF CW response to time-variable loads has been scarcely studied in literature yet. The aim of this study is to test the capability of HYDRUS-CWM1 to simulate the behavior of HF CWs subjected to unsteady loads. Hence, we applied HYDRUS-CWM1 to simulate laboratory results of HF CWs subjected to variable COD inflows. The modelling results adequately fit the experimental data, with an almost perfect agreement in global COD removal efficiencies (67 and 68% from laboratory experiments and simulations, respectively), and mean percent error equal to 20 and 31% for effluent COD and NH 4 + concentrations, respectively. The obtained results suggest that HYDRUS-CWM1 can be a powerful tool to simulate the response of HF CWs under time-variable loads. Additionally, more detailed data are shown to be crucial in order to better exploit process-based model tools.

Chlorine-based disinfection agents are known to favor the production of Disinfection By-Products (DBPs), whose concentrations are restricted by international guidelinesto ensure a safe consumption of drinking water. Hence, it is important to understand the behavior of DBPs within Water Distribution Networks (WDNs) to avoid exposure of WDN users to concentrations higher than guideline values. The buildup in chlorate concentration resulting from disinfectant reaction is here simulated with EPANET for two hypothetical WDNs. Results indicate that increases in chlorate concentrations within the WDN are very limited (

Water losses, the portion of water introduced in a pipe network but not consumed by users, represent a significant problem in water distribution system (WDS) management. Modern guidelines suggest to divide the pipe network in clusters, in order to compute a water balance and measure water consumption by each group. These clusters are called district metered areas (DMAs). The division of a pipe network in DMAs is usually realized with a visual exam supported by technical experience. This approach, which is convenient for small WDSs, becomes difficult to apply to large WDSs characterized by thousands of user nodes and pipes. Therefore, it is necessary to have an automatic tool to recognize the affinity degree of neighbouring nodes and to decide how to assign a node to a particular DMA. We propose an automated approach to subdivide pipes, that only requires flow rates through the network. The method has been tested to a large WDS often used as benchmark. The approach successfully divides the pipe network in an acceptable number of DMAs. Each resulting DMA is characterized by a low number of external links and by a proper number of users.

Microbial fuel cells (MFCs) are bioelectrochemical systems able to generate electricity from wetland soils, including paddies, exploiting the microbial decomposition of organic matter. Additionally, MFCs can also be applied as a novel mitigation strategy for emissions of methane (CH4) from paddy fields. The MFC efficiency in reducing CH4 fluxes is still poorly understood, and it is here investigated via a one-dimensional process-based model that simulates the vertical and temporal dynamics of the chemical compounds affecting CH4 fate within paddy soil. The DOC oxidation rate of MFC is modeled assuming a zero-order kinetics proportional to the generated electricity and different anode depths and current densities are tested. By assuming current densities presently achieved in paddies, MFCs are able to reduce up to −27.9%, −16.7%, and −22.0% of daily minimum, daily maximum, and total CH4 emissions, respectively. Moreover, CH4 reductions are even higher (up to −28.1%, −24.1%, and −26.5%) if we assume 5% of the current density developed on laboratory acetate-fed MFC. The system shows a limiting effect of transport processes on the mitigation of CH4 emissions at high current density. In order to maximize the reduction of CH4 emissions, simulation results suggest to place the anode in the middle portion of the superficial layer of paddy soil. The findings demonstrate the need to further investigate and develop this new technology for field-scale applications.

[1] Water exchange between streams and hyporheic zones is highly dynamic, and its temporal variation is related to the hydrologic fluctuations of stream discharge and groundwater levels. Unfortunately, predictions of temporal patterns of exchange are difficult due to the many hydrodynamic and morphodynamic processes that are involved and also to their complex nonlinear interactions. Examples of these processes include the evolution of streambed morphology in response to changing streamflow as well as the feedback on surface flow induced by drag resistance due to evolving bed forms. In this work, we have employed a stochastic method to analyze the temporal dynamics of bed form-driven hyporheic exchange in a stream characterized by subcritical flow and daily discharge variations. The method is an extension of previous studies that includes current-induced alterations of bedform size and celerity and their effect on water exchange. The modeling results show that during high flows, stream water penetrates deeper and for longer times in the sediments. At the same time, the predicted rate of water exchange per unit streambed area decreases because the streambed area occupied by each bed form increases faster than the volumetric rate of stream water exchange induced by the same bed form. This reduction can be compensated by the increase in wetted area with discharge, which may provide additional streambed area for water exchange. One the main finding of the study is that the time-averaged values of exchange flux and depths are quite similar to those modeled for a steady mean discharge, while residence times are somewhat lower. Predicted temporal variations of exchange depths and times around their time-averaged values are moderate compared to steady state values.

[1] Aquatic sediment hosts coupled pore water flow and biogeochemical reactions that mediate water quality across the fluvial corridor including adjacent alluvial aquifers. However, the effect of small-scale variations in sediment hydraulic properties on nutrient transformation occurring within the sediment is poorly understood. We show through numerical flow and transport simulations, for two realistic heterogeneous permeability cases typical of lowland rivers and two idealized homogeneous ones, that there is little difference in the reactive transport fields, the bulk reaction rates, and nutrient sink/source function despite stark differences in flow fields. This is because the reactions are ultimately controlled by characteristic or bulk residence times that are similar for the heterogeneous and homogeneous cases. This is a promising result for predictive models based solely on relative ratios of residence times and reactive time scales.

In low head sites and at low discharges, water wheels can be considered among the most convenient hydropower converters to install. The scope of this work is to improve the performance of an existing breastshot water wheel changing the blades shape, using Computational Fluid Dynamic (CFD) simulations. Three optimal profiles are investigated: the profile of the existing blades, a circular profile and an elliptical profile. The results are validated performing experimental tests on the wheel with the existing profile. The numerical results show that the efficiency of breastshot wheels is affected by the blades profile. The average increase in efficiency using the new circular profile is about 4 % with respect to the profile of the existing blades.

Crop models are widely used for the modeling and prediction of crop yields, as decision support tools, and to develop research questions. Though typically constructed as a set of dynamical equations, crop models are not often analyzed from a specifically dynamical systems point of view, despite its potential to elucidate the roles of feedbacks and internal and external forcings on system stability and the optimization of control protocols (e.g., irrigation and fertilization). Here we develop a minimal dynamical system, based in part on the widely known AquaCrop model, consisting of a set of ordinary differential equations (ODE's) describing the evolution of canopy cover, soil moisture, and soil nitrogen. These state variables are coupled through canopy growth and senescence, the evapotranspiration and percolation of soil moisture, and the uptake and leaching of soil nitrogen. The system is driven by random hydroclimatic forcing. Important crop model responses, such as biomass and yield, are calculated, and optimal yield and profitability under differing climate scenarios, irrigation strategies, and fertilization strategies are examined within the developed framework. The results highlight the need to maintain the system at or above resource limitation thresholds to achieve optimality and the role of system variability in determining management strategies.

Thanks to their efficiency and simplicity of contruction, breastshot water wheels represent an attractive low head hydropower converter. In this work, a breastshot wheel is investigated by numerical simulations, and the results are validated with experimental tests. The average discrepancy between the numerical shaft torque and the experimental torque is lower than 5%. The numerical model is then used to investigate the performance and the hydraulic behavior of the wheel for different numbers of blades (16, 32, 48, and 64 blades) and at different hydraulic conditions. The increase in efficiency from 16 blades to the optimal blades number ranges between 12 to 16% in function of the hydraulic conditions. Empirical laws are also reported to quantify the improvement in efficiency with the blades number. These laws can support the design process of similar breastshot water wheels. The optimal blades number for this kind of wheel is identified in 48.

Fishways are hydraulic structures that allow passage of fish across obstructions in rivers. Vertical slot fishways—VSFs—are considered the most efficient and least selective type of technical fishway solutions, especially due to their ability to remain effective even when significant upstream and/or downstream water level fluctuations occur. The scope of the present study is to perform numerical simulations in order to investigate and compare the hydraulic turbulent flow field in a standard and a simplified version of the most common VSF design. Implications in relation to fish swimming behaviour and fish passage performance are discussed. Different water depths (as well as discharges) were investigated, using a bed slope of 5%, as a reference for low-gradient VSFs with a very limited selectivity that can be used in multispecies rivers in grayling-barbel regions. Results show that maximum values of velocity, turbulent kinetic energy, and Reynolds stresses are higher in the standard design. However, corresponding to slot geometry and orientation, the direction of the main jet in the simplified design is more inclined towards the left side of the pool. This causes the eddy to split into 2 smaller ones; the minimum eddy dimension is reduced from 0.4–0.5 to 0.2–0.3 m. These dimensions are detrimental for fish passage efficiency, being more comparable with fish length (0.15–0.40 m), thus affecting migrating fish stability and orientation. Furthermore, the standard design provides a more straightforward upstream path and wider areas of low flow velocities and turbulence, useful for fish resting. Therefore, it is recommended that the standard design should be preferred over its simplified version, even if its construction costs are around 10–15% higher than the simplified one.

Whereas the beneficial effects of urban vegetation have long been recognized, growing conditions in urban environments, especially for street trees, are typically harsh and limited by low water availability. Supplemental irrigation may be used to preserve aesthetic quality and ability to provide ecosystem services of urban vegetation but requires careful management of available economic and water resources to reduce urban water footprint. To this purpose, decision makers need quantitative tools, requiring few, physically based parameters and accounting for the uncertainties and future scenarios of the hydroclimatic forcing. Focusing on in-row and isolated trees, a minimalist description of street tree water balance is proposed here, including rainfed and irrigated conditions, and explicitly accounting for tree water requirements, growing conditions (in terms of soil properties and extension of bare soil, permeable and impervious pavements surrounding the tree) and rainfall unpredictability. The proposed model allows the quantification of tree cooling capacity, water stress occurrence and irrigation requirements, as a function of soil, plant and climate characteristics, thus providing indications regarding the tree ability to provide ecosystem services and management costs. In particular, an analysis of different planting designs suggests that a balanced design consisting in bare soil and permeable pavement with size equal to the lateral canopy extension is optimal for water conservation, tree cooling capacity and health. The proposed model provides useful indications towards the definition of site-specific guidelines for species selection and planting design, for sustainable urban vegetation

Summary The mixing of stream water and subsurface water in the hyporheic zone is an important function of fluvial ecosystems. Among the factors that drive water exchange between a stream and its sediments, turbulence is the most ubiquitous as rivers are always in turbulent flow regime. However, there is still much uncertainty about the role of turbulent processes in hyporheic exchange, probably because of the complex nonlinearities that characterize the dynamics of turbulent velocity and pressure fluctuations. In this paper, we adopt a numerical modeling approach to investigate the relationship between turbulent pressure properties and the resulting features of surface–subsurface exchange. In particular, we discuss the importance of large coherent structures of turbulence in driving exchange at depths that are much larger than the penetration depth of small turbulent eddies. The results of the numerical simulations elucidate the response of turbulent hyporheic exchange to changes in stream depth.

The generalized collocation method has proved to be a simple and useful numerical approach for the simulation of a number of one- and two-dimensional nonlinear differential problems. Its remarkable efficiency to solve convection-diffusion models is shown in this note. Some typical test cases are dealt with and the good results that have been obtained suggest that the proposed generalized collocation method could be useful to simulate a class of equations usually adopted to describe several important processes in water engineering.

Un total de 175 muestras de suelos fueron recolectadas en la zona noroeste de Santa Fe y sur de Santiago del Estero durante el período 2001-2009. Se realizaron análisis fisicoquímicos (pH, Nitrógeno Total, Nitrógeno Nítrico, Nitrato, Fósforo, Potasio, Azufre y Materia Orgánica) con el objetivo de categorizar las mismas en función a su calidad y aptitud para uso agrícola-ganadero. El perfil de los suelos analizados destaca deficiencias en Nitrógeno (NT = 0,127 ± 0,032%, N-NO3-= 13 ± 10,349 mg kg-1 y NO3- = 56 ± 45,830 mg kg-1) y un potencial de hidrógeno levemente ácido (pH = 6,4 ± 0,623), observándose una marcada tendencia a aumentar la acidificación en los últimos años. La fertilización equilibrada adquiere importancia estratégica a la hora de obtener óptimos rendimientos en los suelos de la zona, y la incorporación de prácticas de manejo conservadoras tales como labranza reducida, aumento de materia orgánica y rotación de cultivos son fundamentales para el desarrollo sostenible de la región.In recent years, there has been an increasing interest in evaluating soil quality and health. The resource soil is a fundamental component of the biosphere, participating in the production of food, fibers and energy and consequently impacting on the environmental quality. The indiscriminate expansion of agriculture added to the inadequate management in many areas has led to the deterioration of soil structure and to the consequent reduction in organic matter levels, affecting the soil chemical and physical fertility. A total of 175 soil samples were collected in the northwestern area of Santa Fe and in the southern part of Santiago del Estero provinces during the 2001-2009 period. Physicochemical analyses were carried out (pH, Total Nitrogen, Nitrate- Nitrogen, Nitrate, Phosphorus, Potassium, Sulfur and Organic Matter) with the objective of categorizing the soil samples according to fertility and aptitude for agricultural-cattle use. In general, soil samples were deficient in Nitrogen (TN = 0.127 ± 0.032%, N-NO3- = 13 ± 10.349 mg kg-1 and NO3- = 56 ± 45.830 mg kg-1) and had a lightly acidic hydrogen potential (pH = 6.4 ± 0.623), showing a greater acidification trend in recent years. A balanced fertilization program is of strategic importance when seeking optimum yields in these areas. The adoption of conservative management practices such as minimum tillage and crop rotation are fundamental for sustainable agricultural development in the region.

The interactions between the stream and the geomorphologic units that compose the stream channel result in an exchange of water, heat, and chemicals that is an important component of the flows of energy and nutrients in the river ecosystem. This exchange is characterized by complex spatial and temporal dynamics that depend on the characteristics of the stream flow and morphology. At present, many studies have addressed the development of spatial patterns of hyporheic exchange that are induced by many geomorphological factors at different scales. However, much less is known about the temporal evolution of the surface–subsurface exchange in response to the dynamics of the stream discharge. In order to investigate this problem, the present work analyzes the influence of streamflow variability on the hyporheic exchange induced by fluvial bedforms. A stochastic approach is employed to generate streamflow series whose statistical properties are representative of streams with different hydrological regimes. The resulting exchange fluxes and travel times are then computed, and the relationships between the streamflow regime and the dynamics of the exchange flux and travel times are investigated. The results show that the mean stream discharge can be used to estimate the average features of the temporal dynamics of hyporheic exchange. Moreover, exchange fluxes and residence times distributions exhibit significant fluctuations, which are tightly related to the coefficient of variation of the streamflow hydrograph.

The article “Ecohydrological model for the quantification of ecosystem services provided by urban street trees”, written by Roberto Revelli and Amilcare Porporato, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 17 February 2018 without open access.

After years of neglect and an almost complete lack of maintenance, the Racconigi Royal Park was in an inevitable and widespread state of decay. This decay also involved the waterways that were designed in the nineteenth-century by Xavier Kurten (1811–1840). The seasonal lack of water and the agricultural needs of the farms around the Park made it necessary, during the planning stage of the restoration project, to consider the practicability and the effectiveness of some measures that were conceived to optimize the operation of the restored waterways, without altering the historical structure of the system. The realization of a hydraulic numerical model of the system, which is briefly illustrated in the first part of this case study, resulted to be the most suitable tool to study different possible solutions of the problem. The model simulations in fact helped the restorers put into effect the right remedies to favour the correct flow of the water, to make the whole historical system more efficient and to make its future maintenance easier.

Chlorine-based disinfection agents are known to favor the production of disinfection by-products (DBPs), whose concentrations are restricted by international guidelines to ensure a safe consumption of drinking water. Hence, it is important to understand the behavior of DBPs within water distribution networks (WDNs) to avoid users' exposure to concentrations higher than guideline values. The build-up in chlorate concentration resulting from chlorinated disinfectants is here simulated with the EPANET 2.0 software for one benchmark WDN serving about 130,000 inhabitants. Chlorate generation was accounted by means of an empirical model, considering different boundary conditions (physicochemical features of raw water, disinfectant dose). The gathered results indicate that increases in chlorate concentration within the considered WDN are narrow. Chlorate neo-formation in the WDN is, however, strictly related to the initial amount of chlorate released by the water treatment plant, i.e., to the input value in the WDN. If chlorate concentration in treatment plants is kept below 700 μg/L (i.e., World Health Organization guideline), depending on the mixing conditions in tanks, the simulation results referred to the considered WDN show that the DBP build-up within the network is limited (in any case lower than 5–7% of the threshold value).

The interaction between surface and subsurface water has a crucial influence on the biochemistry of stream environments. Even though the river discharge and the flow conditions can seldom be considered to be steady, the influence of this unsteadiness on the hyporheic exchange has often been neglected. In this work, a model for the study of hyporheic exchange during unsteady conditions has been developed. The model provides a sound analytical framework for the analysis of the effects of a varying stream discharge on the exchange between a stream and the hyporheic zone. The effects of the unsteadiness on the water exchange flux, the residence time of the solutes in the bed, and the stored mass are quantified. A synthetic example shows the substantial influence of a flood on the hyporheic exchange, and that the application of a steady model can lead to an underestimation of the exchanged mass, even after the flood has ended.

A stochastic model for the evolution of DO and BOD components along a river with independent BOD point inputs has been developed. The model examines the case in which the initial conditions and the concentrations of the inputs are affected by uncertainty. The uncertain quantities are modelled as random variables, for which any kind of probability distribution can be adopted. The possibility of separately analysing the different components of BOD (e.g., CBOD and NBOD) is included. A semi-analytical expression for the joint probability density function (pdf) of the concentrations is derived. The application of this relationship greatly reduces the computation efforts compared to Monte-Carlo methods. A procedure for the analytical determination of the concentration moments is also described.

We derive and discuss the Green’s function of the linearized de Saint-Venant equations (LSVEs) for shallow water waves in channels and rivers. The analysis offers a unified description of previous results on LSVEs regarding, in particular, the existence of three simple linear waves whose interplay determines all the evolution of the solution, the role of the Froude number (F) in all its range of variability (both in subcritical and supercritical conditions), and the physical reason of the instability for F>2 and its convective nature.