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Decision-makers need tailored information regarding future climate, land use, forest management and societal scenarios for sustainable watershed management. Such information can be attained by integrating the water-energy-land nexus approach with climate services. To support decision-makers from Brașov metropolitan area (Romania), we co-developed land use, forest management and societal scenarios and analysed their impact on the water-energy-land nexus under climate change. We applied the Soil and Water Assessment Tool (SWAT) to the Săcele reservoir from the Tărlung river basin in order to spot the interrelations between nexus components under different climate and societal scenarios. In particular, we applied four bias-corrected GCM & RCM model combinations for two climate scenarios RCP4.5 and RCP8.5, nine land use and forest management scenarios, and twelve societal scenarios. Modelling results were analysed between 2020 and 2099. The results for the study area indicate that the projected average annual precipitation is close to historical averages in most climate scenarios explored, while the projected average annual temperature is increasing. Furthermore, the analysed data suggest an increase in severe dry intervals from approximately 6% (for the period 1961–2013) to 12% by the end of the 21st century, indicating that precipitation variability may change considerably. The SWAT model results show no significant changes in the water flow under different forest management scenarios. In contrast, model results for scenarios that imply forests' clearcutting and their replacement with pastures or meadows indicate that water quality is affected by increased sediment flow. Regarding the number of months with water scarcity in the Săcele reservoir (i.e. water demand exceeds water supply), we found an increase from 0.4 months in 2020 to 1.5 months in 2099. The model results also revealed that climate change significantly influences the water supply in the reservoir. To conclude, the regional stakeholders highly value the model results for the co-developed scenarios, which have been already used to promote sustainable resource management.

The present study evaluates the applicability performance of the Soil and Water Assessment Tool (SWAT) in small forested watersheds (less than 1000 km2). This open-source software is widely used in investigations focused on water availability and quality. Overall, SWAT model performance ranges between satisfactory to good. Normally, underestimates daily peak discharges. The limitations of the model are related to the accuracy of climate data used and to the time period used for validation. Watershed area, forest cover and streamflow spatial distribution have an important influence on modeling processes. Overall, from the analyzed studies, we observed for discharge a decreasing tendency, more pronounced towards the end of the 21st century (up to −54%). For surface runoff, was noticed the same decreasing tendency up to 41%. Regarding sediment yield, the results vary within very wide limits. These findings vary according to watershed location, scenarios adopted, and the eligible period of time.

The management of torrential flood risk areas located in natural protected sites requires special approaches. Also, those processes can cause casualties and damage socioeconomic structures (roads, railways, houses, etc.) The processes intercept protected landscapes, sometimes endangering protected species and habitats. The restoration of the streambed's stability in protected areas and the protection of the economic objectives affected by the torrential floods, imply special measures of planning. The planning measures are based on the use of ecological materials and technologies with minimal impact on the environment. The article presents a methodology for identifying small river basins with high torrential risk and the endangered economic objectives, as well as applying this methodology into three Natura 2000 sites from central Romania (ROSCI0207 Postavaru, ROSCI0195 Piatra Mare and ROSCI 0038 Ciucas). Identification of the basins was made considering their geomorphological and hydrological characteristics and the vulnerability of the intercepted socio-economic objectives. Into identified watershed, measurements of the streambed topography and the geometric characteristics of the endangered structures were made. Based on hydraulic simulations, maps were generated for floods with a 100-year return period. Using these flood maps, the maximum water level was determined to highlight the flood risk areas for each socioeconomics structural objective. In areas identified as floodplain, special structural and nonstructural solutions are proposed for guiding water into convenient paths to avoid the endangered structures.