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Climate change has intensified the effects of habitat fragmentation in many ecosystems, particularly exacerbated in riparian habitats. Therefore, there is an urgent need to identify keystone connectivity spots to ensure long-term conservation and sustainable management of riparian systems as they play a crucial role for landscape connectivity. This paper aims to identify critical areas for connectivity under two contrasting climate change scenarios (RCP 4.5 and RCP 8.5 models) for the years 2030, 2050 and 2100 and to group these critical areas by similar connectivity in keystone spots for sustainable management. A set of analyses comprising climate analysis, drainage network analysis, configuration of potential riparian habitats, riparian habitat connectivity, data clustering, and statistical analysis within a Spanish river basin (NW Spain) were applied. The node and link connectivity would be reduced under the two climate change scenarios (≈2.5 % and 4.4 % reduction, respectively), intensifying riparian habitat fragmentation. Furthermore, 51 different clusters (critical areas) were obtained and classified in five classes (keystone spots) with similar connectivity across the different scenarios of climate change. Each keystone spot obtained by hierarchical classification was associated with one or more climate scenarios. One of these keystone spots was especially susceptible to the worst climate change scenario. Key riparian connectivity spots will be crucial for the management and restoration of highly threatened riparian systems and to ensure long-term biodiversity conservation. • Connectivity importance was reduced under different climate change scenarios. • Critical area detection for connectivity conservation is threatened by climate change. • Critical areas were classified with similar connectivity keystone spots against climate change. • Keystone spots with high PC index will be priority for conservation management. [ABSTRACT FROM AUTHOR]

The Soil and Water Assessment Tool (SWAT) is a well-established eco-hydrological model that has been extensively applied to watersheds across the globe. This work reviews over two decades (2002–2022) of SWAT studies conducted on Mediterranean watersheds. A total of 260 articles have been identified since the earliest documented use of the model in a Mediterranean catchment back in 2002; of which 62% were carried out in Greece, Italy, or Spain. SWAT applications increased significantly in recent years since 86% of the reviewed papers were published in the past decade. A major objective for most of the reviewed works was to check the applicability of SWAT to specific watersheds. A great number of publications included procedures of calibration and validation and reported performance results. SWAT applications in the Mediterranean region mainly cover water resources quantity and quality assessment and hydrologic and environmental impacts evaluation of land use and climate changes. Nevertheless, a tendency towards a multi-purpose use of SWAT is revealed. The numerous examples of SWAT combined with other tools and techniques outline the model's flexibility. Several studies performed constructive comparisons between Mediterranean watersheds' responses or compared SWAT to other models or methods. The effects of inputs on SWAT outputs and innovative model modifications and improvements were also the focus of some of the surveyed articles. However, a significant number of studies reported difficulties regarding data availability, as these are either scarce, have poor resolution or are not freely available. Therefore, it is highly recommended to identify and develop accurate model inputs and testing data to optimize the SWAT performance. [Display omitted] • SWAT review on Mediterranean hydro-climatic studies. • Lack of SWAT assessment on Mediterranean catchments. • A comparison of data from different Mediterranean basins. • Enhancing data availability for SWAT applications. • Developing a comprehensive knowledge of Mediterranean watersheds. [ABSTRACT FROM AUTHOR]

The management of environmental flows is of paramount importance in regulated water resources systems to preserve river ecosystems. This work proposes a methodology to assess habitat alteration in river basins altered by management activities. The methodology is based on the joint application of a basin management model (SIMGES, AQUATOOL) and a model to estimate habitat time series (CAUDECO). CAUDECO is based on the weighted useable areas of the species in their different vital stages that, in turn, depend on the flows in each river stretch and the biological periods of the species. The final output is an indicator of habitat alteration, which is defined ad hoc for this work to relate the habitat suitability under regulated and natural regimes. The methodology was applied to a case study in north-western Spain: the Órbigo River basin. The results in the current management scenario highlight that the ecological flows improve the habitat suitability of several species with respect to natural regime conditions. For instance, the mean values of the habitat time series in the Órbigo River for the brown trout and bermejuela under regulated conditions are 69.6% and 88%; whereas in natural regime they are equal to 55.1% and 72.9%, respectively. Based on these results, eight additional scenarios of ecological flows were tested and their effects on both habitat alteration and water demand reliability were quantified and discussed. It was found that increases in the ecological flows up to 30% do not affect the reliability of water demands and reduce habitat alteration (i.e., lead to values of the habitat alteration indicator closer to 1) for all species present in the river basin. These results highlight that the methodology and indicator of habitat alteration proposed in this paper are useful to support the management of regulated river basins, since they allow assessing the implications of ecological flows on both habitat suitability and reliability of water demands. • A methodology is proposed to assess habitat alteration in regulated basins. • The methodology is applied to the Órbigo River basin (north-western Spain). • Environmental flows can improve habitat suitability compared to natural conditions. • Increases in environmental flows reduce habitat alteration for all species. • Rises in environmental flows up to 30% do not affect the reliability of water demands. [ABSTRACT FROM AUTHOR]

Despite major recent advances in socio-hydrology and hydroeconomics research, interdisciplinary methods and models for water policy assessment remain largely concealed to the academic arena. Most river basin authorities still base decision-making on inputs from hydrologic Decision Support Systems (DSS), and have limited information on the economic costs that water policies may impose on the economy. This paper presents a time-variant hierarchical framework that connects a hydrologic module and an economic module by means of two-way feedback protocols. The hydrologic module is designed to fit the AQUATOOL DSS, the hydrologic model used by Spanish river basin authorities to inform decision-making at a basin scale; while the economic module is populated with a Positive Multi-Attribute Mathematical Programming (PMAMP) model that represents the behavior and adaptive responses of irrigators. The proposed hierarchical framework is used to assess the economic repercussions of strengthening irrigation quotas so to achieve minimum environmental flows in the Douro River Basin (Spain) under climate change. Results show that reductions in agricultural water allocations to meet environmental flow requirements create nonlinear incremental profit and employment losses in irrigated agriculture that are on average low to moderate (between −4% and −12.9 % for profit, and between −4.6 % and −12 % for employment, depending on the scenario). During extreme droughts, the abrupt reductions in water availability and agricultural allocations can test farming systems past the breaking point and lead to catastrophic profit and employment losses (>80 %). • Water authorities have limited information on the economic costs of environmental flows. • We couple a microeconomic model with the widely used DSS AQUATOOL. • The coupling relies on a modular, protocol-based, time-variant hierarchical framework. • Water restrictions create nonlinear incremental profit and employment losses. • Extreme droughts test farming systems past breaking point and catastrophic losses. [ABSTRACT FROM AUTHOR]