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This paper analyses decadal climate phenomena and the phases of the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO), and assesses the climate–water–energy nexus at the reservoir system of the São Francisco River Basin (SFRB), Brazil. This study brings a non-traditional approach focused on the link between climatic patterns and hydrological processes and their social-economic consequences, such as their effect on energy production. The methodology used data from the precipitation, natural streamflow, and AMO and PDO series. These variables were evaluated by wavelet transform analysis (WTA), flow duration curve (FDC), streamflow that is equalled or exceed ed 90% of the time (Q90), the reliability index (RI) for different demands and the hydropower generated. The results suggest that the WTA for the SFRB was more significant on the inter-annual scale, and the period with opposite phases of AMO(−) and PDO(+) showed the highest values of FDC, Q90, RI and hydropower generated simulated for the SFRB. [ABSTRACT FROM AUTHOR]

This paper investigates climate change impacts on the hydrology and water quality of Brazilian semi-arid reservoirs. An integrated approach coupling climate, hydrological and water quality models was proposed. Five general circulation models (GCMs) and two future scenarios (SSP2-4.5 and SSP5-8.5) were used for the projections. The simulations showed that uncertainty in climate forecast significantly impacted hydrological and water quality outputs. Some scenarios revealed a strong decrease in streamflow and storage volume. On the other hand, 40% of multi-GCM projections indicated reservoir eutrophication. The impacts on hydrology and water quality under SSP5-8.5 were more significant than those under SSP2-4.5. The results also indicated that drought events may be prolonged under climate change, principally at the end of the 21st century for SSP5-8.5, and may significantly increase the total phosphorus concentration. This suggests that tropical semi-arid reservoirs could be more vulnerable to eutrophication in scenarios of climate change than those in other regions. [ABSTRACT FROM AUTHOR]

Socio-hydrology has recently garnered attention as a promising research paradigm among hydrologists. In this paper, we argue that viewing the socio-hydrological systems as a network of causal factors can assist in these efforts by revealing emergent properties of socio-hydrological systems. These factors, which are neither actors nor affiliations but symbolic representations of miscellaneous phenomena, represent the key variables affecting socio-hydrological system behaviour. Despite being crucial for understanding system dynamics, these factors are not captured by most equations of coupled human–water coevolutionary models. To demonstrate our method, we use qualitative case study research to analyse the Jaguaribe Basin in Ceará State-Brazil as a network of factors, i.e. mental conceptions, and representations of water resource management experts. We show that most results are unsurprising, exhibiting expected causal relationships. However, there was at least one unexpected result, which showed that the variable "conflict" was the single most sensitive variable to systemic evolution. [ABSTRACT FROM AUTHOR]

The association of hydrological models with remote sensing data allows the estimation of parameters that cannot be easily measured in situ, especially in regions with poor monitoring networks. In this paper, a distributed hydrological energy water balance model (FEST-EWB) was calibrated and validated in a basin located in a climate transition zone between a semi-arid region and the humid Atlantic Forest, in Brazil. Land surface temperature (LST) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) were used to calibrate the model, that solves the system of energy and mass balance equations as a function of the representative equilibrium temperature. For validation, soil moisture and LST data collected in situ were used. The model presented good performance for the simulation of the variables studied in the basin, even with reduced availability of MODIS data due to cloud coverage, allowing the use of FEST-EWB in areas with these characteristics, which are common in many regions of the world. [ABSTRACT FROM AUTHOR]

The city of São Carlos, state of São Paulo, Brazil, has a historical coexistence between society and floods. Unplanned urbanization in this area is a representative feature of how Brazilian cities have developed, undermining the impact of natural hazards. The Gregório Creek catchment is an enigma of complex dynamics concerning the relationship between humans and water in Brazilian cities. Our hypothesis is that social memory of floods can improve future resilience. In this paper we analyse flood risk dynamics in a small urban catchment, identify the impacts of social memory on building resilience and propose measures to reduce the risk of floods. We applied a socio-hydrological model using data collected from newspapers from 1940 to 2018. The model was able to elucidate human–water processes in the catchment and the historical source data proved to be a useful tool to fill gaps in the data in small urban basins. [ABSTRACT FROM AUTHOR]

Brazil has some of the largest rivers in the world and has the second greatest flood loss potential among the emergent countries. Despite that, flood studies in this area are still scarce. In this paper, we used flood seasonality and trend analysis at the annual and seasonal scales in order to describe flood regimes and changes across the whole of Brazil in the period 1976–2015. We identified a strong seasonality of floods and a well-defined spatio-temporal pattern for flood occurrence. There are positive trends in the frequency and magnitude of floods in the North, South and parts of Southeast Brazil; and negative trends in the North-east and the remainder of Southeast Brazil. Trends in the magnitude (frequency) were predominant in the winter (summer). Overall, floods are becoming more frequent and intense in Brazilian regions characterized by wet conditions, and less frequent and intense in drier regions. [ABSTRACT FROM AUTHOR]