Stefano Casadei

Estimating ecological flows is essential in rivers to achieve the objectives defined by the EU Water Framework Directive 2000/60/EC (WFD). In the framework of an agreement with the Autorità di Bacino Distrettuale dell’Appennino Centrale, the work aims to present the results of an integrated approach developed to consider various factors affecting the river’s ecological flow (hydrological, hydrobiological, hydrogeological, hydro-morphological, and hydrochemical). The present study focuses on the Nera River, a main tributary of the Tiber River, which is primarily fed by groundwater from limestone aquifers. The river catchment hosts strategic water resources that are crucial for providing drinking water and sustaining aquatic ecosystems. Moreover, river water is utilized for hydropower generation, fish farming, and various recreational activities along the river. The ecological status was rated as good based on the New Index of the Ecological Status of Fish Communities (NISECI), along with physicochemical characterization of river water and hydromorphological characteristics as criteria for its definition. Based on a regional model specifically developed for brown trout of rivers in the Tiber River basin (thus applicable to the Nera River), the minimum ecological flow was set at approximately 2.92 m³/s. Based on flow-duration curves, the average and maximum ecological flow values were also identified as 3.71 and 5.07 m³/s, respectively. The analyses carried out by the Water Exploitation Index Plus (WEI+) revealed medium-to-high stress in the catchment; therefore, withdrawals should be carefully re-planned to minimize further impacts on water-dependent ecosystems. The approach proposed for the Nera River highlights the importance of conducting focused, multidisciplinary studies in areas where groundwater withdrawals interact with groundwater-dependent ecosystems, thereby supporting regional management plans that address the needs of both humans and aquatic ecosystems.

In the upper Tiber River basin, in the region of Umbria, there are hydraulic works built by the Etruscan and Roman peoples whose origins date back to several centuries before Christ. Some of these structures have been updated over the centuries and are still in use today, and they play important roles in water resource management. Owing to these historical infrastructures, cultural and social collateral activities have developed, which, together with the economic functions of these works, are of enormous relevance to Umbrian populations. However, the history of these hydraulic systems also serves as an example of the evolution of hydraulic engineering for all humanity. This paper is aimed at illustrating four of these fundamental systems: i) The Sportone di Maderno on the Clitunno River, which was named after the architect who designed it. This architect was also responsible for the façade of St. Peter’s Basilica in Rome, which is an efficient historical work that enables water drainage. ii) The Marmore Falls, which is an ‘artificial’ waterfall that exemplifies the global significance of water and its influence on art and technology throughout history. iii) The Monte Pacciano reservoir in Perugia, which has a capacity of approximately 6,000 m ³ and is part of an ancient medieval aqueduct. Finaly, iv) the hydraulic axis of the Clitunno River, which is a key element in the economic development and liveability of the Umbrian Valley over the centuries. This article and the case studies it describes are aimed at highlighting the importance of preserving these ancient hydraulic systems and emphasising the opportunity for extending this study to other historical systems.

The purpose of this study is to assess the possibility of relating two phenomena: first, meteorological drought, which is exclusively dependent on climate; second, water scarcity and its uses, which are predominantly anthropogenic in nature. Sometimes these phenomena may overlap, with the former amplifying the latter, but direct correlation is not always highlightable due to the anthropogenic character of water shortage and the variability of water supply sources. In the literature, many papers evaluate these two phenomena separately: in particular, the SPEI (Standardized Precipitation-Evapotranspiration Index) is widely used for detecting meteorological drought, while the link between water shortage and its uses is assessed through an index of water resource exploitation, WEI⁺ (Water Exploitation Index Plus), which is based on the calculation of an anthropogenic factor, withdrawals net of restitutions. Specifically, this study examines the SPEI and WEI⁺, respectively, calculated for the July–August–September quarter (SPEI3 sept) and during the low-flow period (WEI⁺_EF low flow), according to the environmental flow constraint. These periods are considered seasonally overlapping in the study area of the Umbria region. The results analyzed by spatial method show the more critical areas, where SPEI3 sept and WEI⁺_EF overlap their critical values, respectively, <−1.0 and >100%. The proposed methodological approach provides stakeholders in the water sector with essential information to adopt a proactive approach to drought phenomena.

The work aims at developing a multidisciplinary strategy for the monitoring, assessment, valorization and possible use of small reservoirs in the framework of resilient water resources management. Specifically, we focus on water quality and quantity analysis using an integrated approach between remote sensing data and in situ observations. The topic is part of the SIGHTING- Small reservoIrs restoration: Green blu-infrastructures to enHance rural area resilience To clImate change-project, that is devoted to the study of lakes in the upper Umbria Region (Central Italy).First, available satellite data, coupled also with the Google Earth Engine (GEE) platform, are used to investigate in the last decade, the spatial distribution, the seasonal variations and the inter-annual variations of target water quality parameters such as the chlorophyll Chl-a concentration and turbidity. Different products with increasing spatial resolution. e.g. Sentinel -2 and Planet-Scope (from 20m to 3.7m), freely available for research use, are tested. These data, acquired with a regular revisit time of few days, allows a continuous monitoring of the water resource.The procedure is validated for a pilot cases study, calibrating derived results on the base of in situ monitoring data. In July 2024, the water quality survey has been conducted on a small shallow pilot study lake, of about 33200 m2, collecting 20 samples for chemical and physical analysis. The procedure, even if limited to a pilot case study, allows to establish the potentialities and weakness of the free satellite data used, also in the context of a possible extension to a largest spatial scale (regional/national).

The study aims at investigating strategies to reduce the effect of the nutrients pollution in Piediluco lake, improving the water quality and limiting the eutrophication processes. In particular, managements options operating in the body of the reservoir are considered, i.e. the variation and/or repositioning of the main water inflow.Piediluco is the second largest lake of Umbria region (Central Italy) and is characterized by an extended and complex shape with several branches (approximately 1,7 km2 with an average and maximum depth, respectively, of 10 m and 20 m). Currently, the hydraulic regime of the lake is regulated by the downstream hydroelectric plants of Galleto and Monte Sant’Angelo: during the power generation, water from Piediluco lake is conveyed through Velino river into the hydroelectric plant; when the electric production is paused, the entire flow rate of Velino river is conveyed to the lake. Actually, the largest water supply is provided to the lake by the Medio-Nera channel, an artificial canal built in 1932 that has expanded the Piediluco basin area from 75 km2 to 2100 km2. The main idea is to move the position of the inlet in order to promote the movement and recirculation of water throughout the lake surface.Several field measurements, carried out from the first years of 1980s, have highlighted that the health of the lake has been constantly deteriorating: the increase of nutrients loading has negatively affected the ecosystem, progressively compromising the use of the lake and its resources, and, consequently, the local economy. A high eutrophication level of the lake, with algal bloom and, in extreme meteorological conditions, a significant water anoxia, in particular in the arms of the lake far from the inlet of Medio-Nera channel, have been observed.The work is based on an integrated approach: at first stage, remote sensing available data, coupled with the Google Earth Engine (GEE) platform, are used to analyse, in the last decade, the spatial distribution, the seasonal variations and the inter-annual variations of water quality parameters. Secondly, a two-dimensional model is developed, in order to simulate the sediment and pollutant transport connected with the hydrodynamic condition of the lake with different management scenarios. The model is calibrated and validated on the base of in situ monitoring data.

This study aims to outline governance actions to mitigate impacts of climate change scenarios (drought) in Lake Trasimeno. A water balance model was integrated with a decision support system to evaluate water levels and water management scenarios. Water quality indices, based on Sentinel-2 images, allow the monitoring of parameters such as chlorophyll-a and turbidity. The possibility of diverting water volume from Montedoglio or Casanova reservoirs into Trasimeno Lake, according to the hypothesis of different “intervention thresholds levels” and volumes immitted, is investigated. Simulation results show that hydrometric zero represents the optimal threshold, maximising the volume supplied and mitigating a water level decrease. An inverse correlation between the lake water levels, turbidity, and chlorophyll-a concentration indices was observed. Even if further studies to test the effects of mixing water with different physical and chemical characteristics are necessary, the proposed mitigation strategy could avoid the rapid growth of the above-mentioned quality parameters.

The 18th World Lake Conference, entitled “Governance, Resilience, and Sustainability of Lakes for a Better Society” was held virtually from November 9th to 11th, 2022 at the University of Guanajuato, Mexico. This forum was designed with the primary objective of providing a space where scientists, professionals, students, managers, and practitioners could propose, share, and learn about studies, strategies, and actions which enhance the management of lakes around the world. Different activities were contemplated and scheduled in the organization of this forum, such as conferences, special sessions, technical sessions, and workshops where 194 distinguished investigators and participants shared the results of their research and the knowledge they have gained over the years.