The Water Exploitation Index (WEI), or withdrawal ratio, is an indicator of water scarcity, which has been updated into its WEI⁺ form by the Committee of Experts of the European Commission. In calculating the total abstraction of fresh water, this indicator also includes the possible return flow and management rules. The demand for freshwater and long-term freshwater resources are both necessary to calculate the WEI⁺. These values are not easy to assess at basin or sub-basin level and, for this reason, WEI values are generally calculated at the country level. This paper introduces a new approach to calculate the WEI⁺, with the purpose of extending its use to basin and sub-basin levels. The methodology is based on flow duration curve estimation, which evaluates freshwater resources, and a Web-GIS system that evaluates water abstractions distribution. This approach allows for the assessment of locally stressed areas in the hydrographic network and could provide a fundamental step toward more comprehensive regional water resources management plans. The new methodology is tested in some sub-basins of the Upper Tiber River Basin (Italy). These results contribute to the analysis of water withdrawals sustainability, based on the policy of the European Environment Agency, which is aimed toward the development of a proactive approach for reducing water stress.

Small reservoirs are widely used for storing water, especially for irrigation purposes. During the last decades, in Italy many of these reservoirs have been dismissed, becoming an untapped resource. As a matter of fact, maintenance problems connected to these structures together with their natural tendency to silt have favored the use of other water supply resources such as withdrawal from wells. The increase of drought periods and the high water volume demand for agricultural purposes suggest to evaluate a full and rational use of all water resources, leading to a rediscovery and enhancement of untapped resources. Specifically, this research focuses on small reservoirs and on their potential contribution to a sustainable water management in agriculture. Unfortunately, there are no reliable data on their number, spatial distribution and potential storage volume. The aim of this work is to define reservoir spatial distribution and evaluate potential available water volumes. The upper Tiber river basin has been selected as a case study for the methodology proposed. The work starts from the acquisition and re-elaboration of the old census of small reservoirs, evaluating, through GIS and regression techniques, the distribution over the territory and the available volumes. Then the reservoir census and the derived database were updated for the period from 2015 up to 2019 introducing combined computational procedures of remote sensing techniques and GIS, based on satellite images and water index calculation. The results of the semi automatic procedure used show good performance in lake identification, making it a promising tool for a fast and reliable water body identification and evaluation in wide areas.

Problems in the sustainable exploitation of water resources are mainly due to the spatial distribution of uses and are worsened by uncontrolled withdrawals by different activities. In this context, in order to evaluate and manage the available water resources, a decision support system has been developed to support the decision-making processes. This system was implemented on a web platform, in order to manage spatial data and to analyze information on water resources. The system also integrates a WEB-GIS engine for the elaboration and regionalization of data over the river network. The web architecture also makes these tools widely accessible and easily shareable by all stakeholders. The Web-based application was tested successfully in the Tiber River Basin (Central Italy) and focuses on the building of a hydrological database together with an evaluation model for surface water resources. The results provide synthetic information on the sustainability of water allocation scenarios, with particular regard to the feasibility of allowing new dissipative water withdrawal, such as dissipative water use in agricultural production for precision irrigation. The software technology of this project relies on open source code and can also be applied in other fields for the sustainable management of environmental resources.

Lake Trasimeno is a closed lake in Central Italy and in historically its water level has been affected by wide fluctuations mostly depending on the climate. The lake has suffered many water crises due to water scarcity and in recent decades, droughts have also severely affected the economic and environmental situation. The aim of this study was to analyze the possibility of limiting these severe level fluctuations by evaluating of feasible water resource management policies that could also reduce the environmental stress of this area. Therefore, a specific decision support system (DSS) has been developed in order to simulate different scenarios for the entire water system of the Trasimeno area. In particular, the hydrological model implemented in the DSS allowed for the simulation and validation of different management policy hypotheses for the water resource in order to mitigate environmental and water crises for the Lake Trasimeno. Results indicated that it is possible to transfer a certain amount of water from nearby reservoirs without affecting the availability of the resource for specific users. In this way, Lake Trasimeno can benefit both from an increase in water levels in the lake, so a possible better situation in quantitatively and qualitatively.

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.