Vertical slot fishways are increasingly common structures for the passage of a wide variety of migratory fish and contribute to the maintenance of fish diversity in fragmented rivers. These structures are designed with several geometric arrangements and, consequently, flow patterns through them can be shaped to present suitable characteristics for the fish species. To aid in the design of vertical slot fishways, a three-dimensional numerical model was used to simulate the flow for different geometric configurations. An existing vertical slot fishway with nonstandard dimensions was initially modeled and validated. This geometry was used as a reference design. Modifications to the reference design, such as the insertion of cylinders, changes in the baffle shape and position of the vertical slots, as possible rehabilitation measures, were proposed and tested. In summary, five different designs were evaluated with several slopes, totaling 17 geometries. Hydraulic parameters, flow patterns, maximum velocities, velocity fields and turbulence kinetic energy in the pools were analyzed. The results indicate that the maximum velocity values were between 9% and 68% higher than those obtained by the theoretical equation. This indicates that maximum velocities can be underestimated for nonstandard vertical slot fishways if a simplified evaluation is conducted. The insertion of cylinders in the region close to the slot reduces the maximum velocity up to 8.2%. The positioning of the vertical slots on alternating sides increases the maximum values of turbulence kinetic energy and the regions subjected to higher values. However, this configuration provided greater energy dissipation and reduction of velocities by up to 27%. Thus, modifications in nonstandard vertical slot fishways can be useful in future design or rehabilitation of existing structures in order to provide velocities and turbulence more friendly for a higher number of fish species.

Vertical slot fishways allow energy dissipation as a function of the pool, longitudinal slope, baffle and vertical slot design. The mean and turbulent flow patterns in these structures must be compatible with the fish target. The design of these structures is commonly based on previous successful fishways as well as simplified theoretical equations and empirical relationships. To aid in the design of these structures, a three-dimensional hydrodynamic model was used to simulate the flow, and experimental studies were used to validate the model. The mean velocities, pressures and parameters indicative of turbulence were analyzed. The maximum flow velocities were up to 32% higher than the values obtained using a simplified theoretical equation. The evaluation of the volumetric dissipated power indicated that the mean value for the pool was lower than 150 W/m3; however, analysis of the spatial distribution showed that in some areas, the values can exceed 1000 W/m3. The results indicate that the numerical simulation was able to adequately represent the flow considering the computational cost involved. Accordingly, it can be used as a complementary tool for the design of new fishways and for the analysis of modifications in existing ones.

Drought events have been reported in all Brazilian regions every year, evolving slowly over time and large areas, and largely impacting agriculture, hydropower production, and water supplies. In the last two decades, major drought events have occurred over the country, such as the 2010 and 2015 events in the Amazon, the 2012 event in the Pampa, and the 2014 event in the Cerrado biome. This research aimed to understand drought propagation and patterns over these biomes through joint analysis of hydrological, climatic, and vegetation indices based on remote sensing data. To understand the drought cascade propagation patterns, we assessed precipitation, evapotranspiration, soil moisture (at surface and sub-surface), terrestrial water storage, land surface temperature, enhanced vegetation index, and gross primary productivity. Similar drought patterns were observed in the 2015 Amazon and 2012 Pampa droughts, with meteorological and agricultural droughts followed by a hydrological drought, while the 2014 event in the Cerrado was more associated with a hydrological drought. Moreover, the 2015 Amazon drought showed a different pattern than that of 2010, with higher anomalies in precipitation and lower anomalies in evapotranspiration. Thus, drought propagation behaves differently in distinct Brazilian biomes. Our results highlight that terrestrial water storage anomalies were able to represent the hydrological drought patterns over the country. Our findings reveal important aspects of drought propagation using remote sensing in a heterogenous country largely affected by such events.