correction to ecohydrological model for the quantification of ecosystem services provided by urban street trees

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

Performance Optimization of Overshot Water Wheels at High Rotational Speeds for Hydropower Applications

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 (80%–85%) is constant for rotational speeds below the critical speed, whereas the efficiency linearly decreases at higher rotational speeds due to the increase of water losses at the inflow. To improve the efficiency when the rotational speed is above the critical speed, an improved geometric design was investigated by implementing a theoretical model validated using experimental results. The new geometry consists of a circular wall around the periphery of overshot water wheels. The wall redirects into the buckets the water flow that is lost at the inflow, improving the efficiency up to 1.5 times at high rotational speeds

Urban hazard adaptation: efficiency of a Green Infrastructure in an Italian metropolis

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

cfd simulations to optimize the blade design of water wheels

Abstract. 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

Ecosystem services evaluation for a more resilient urban environment

Among the Sustainable Development Goals defined in Agenda 2030 by United Nations, Number 11 aims to achieve more resilient urban environments facing the ongoing climate change. “Ecosystem Restoration” is one of the solutions to help achieving this goal, by restoring habitats and functions of the terrestrial and marine ecosystems on which flora and fauna depend. At urban scale, a method for the evaluation of the Ecosystem Services (ES) offered by a given green area is reported: among the quantifiable benefits, in this work the attention is paid to the quantity of surface water runoff that vegetation is able to reduce, through processes of infiltration, evapotranspiration and storage. The results of a case study on a Turin green space are shown as an example, deepening the species efficiency in providing the total amount of 735 cubic meters of water saved

CFD simulations to optimize the blades design of water wheels

Abstract. 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. </jats:p

Ecohydrological model for the quantification of ecosystem services provided by urban street trees

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