Excess sediment is one of the main agents of water pollution, affects the aquatic ecosystem and causes siltation problems in reservoirs and rivers. Bottom sediments are coarse and easily deposited, being the major responsible for morphological alterations in rivers. Therefore, is important to estimate the amount of sediment transported in other to establish mitigation strategies and recovery of affected areas. There are several methodologies for estimating bedload transport: equations, numerical modeling, direct physical sampling, and indirect method measuring dune tracking. Most studies measure bedload transport using the equipment Helley-Smith, generally taken as reference value for other methods. However, Helley-Smith causes changes in the flow field, often resulting in overestimates in sand bed rivers. Those overestimates were not yet described and quantified in detail. This article tries to solve this gap by observing the Helley-Smith sampler at the time of sampling. For this, we used a video camera recording processed by Particle Image Velocimetry (PIV) technique to qualitatively evaluate changes that the intrusive sampler causes in the displacement of bottom sediments in a sand bed river. When the sampler was properly allocated to the bottom, PIV resulting velocity maps of bedload particle transport identified the acceleration of the bottom particles as they approached the mouth of the sampler. We also noticed areas of convergence and vorticity of the sediments towards the sampler’s mouth, which may overestimate sampling. When the sampler’s mouth was disconnected from the bed due to the morphology of the bottom, we find regions of divergence in the displacement of the sediments creating unrealistic results for bedload transport analysis. In addition, the presence of organic matter can be underestimated, which causes difficulties in analyzing the quality of the collections because it is not possible to guarantee an equity in the positioning of the equipment at the bottom of the channel. We thus recommend complementation Helley-Smith measurements with surrogate methods, for example such as using ADCPs or optical methods, as the one described here.

Brazil is one of the richest countries in water resources and is currently the second largest global supplier of food and agricultural products. Furthermore, more than 70% of Brazilian energy comes from hydropower. Therefore, to ensure water availability for future generations it is necessary to consider the Nexus thinking (water, food, energy, ecosystem service, and social aspects integrated) in the country. However, few studies have been developed considering the Nexus thinking in Brazil. Understanding the interconnected risks and vulnerability to these sectors under climatic change conditions is crucial for the development of sustainable resources management plans and for mitigating competition among them. Here, we assess the Food-Energy-Water Nexus considering climate and land cover and land use changes (LCLUC) scenarios in the São Francisco river basin. This basin is the third largest basin in Brazil and supplies water to approximately 14 million inhabitants, with the Metropolitan Region of Belo Horizonte being the most populous area. The São Francisco river has been used for water supply, irrigation, agriculture and transportation by waterways, but its preponderant use is for hydroelectric power generation. However, this basin has been suffering from LCLUC and drought that has plagued the region since 2012. In addition, part of the river flow has been diverted due to the transposition of the São Francisco river to supply water to the semi-arid region of Brazil. We will calibrate and evaluate the Soil and Water Assessment Tool (SWAT) using hydrometeorological data from 1972 to 2017. We will also use LCLUC scenarios from the OTIMIZAGRO model and regional climate change models (HadGEM2-ES and MIROC5, RCP 4.5 and 8.5). Then, we will compute the demands of water by different sectors and integrate water availability and demand to reach an optimal water use based on the Nexus thinking. Our results will provide decision-makers with information regarding the risks and trade-offs and will support water resources management decisions in order to allocate scarce water resources toward food or energy.

Water erosion triggers the spending of billions of dollars a year to Brazil, as well as social and environmental issues. One of the strategies to minimise soil erosion and to foster economic development is adopting techniques for the integration of agricultural systems. Nevertheless, studies on long-term experimental fields under integrated systems are scarce regarding the effect of the integrated crop, livestock, and forestry system on soil and water loss. As integrated agricultural systems are popularising, especially in the Brazilian Cerrado, it is key to understand their impacts on the erosive processes. As experimental data are fundamental to develop and assess mathematical models, the lack of such information halts the advance of technologies that support agricultural development. Here, we assess the influence of integrated crop, livestock, and forestry systems on interrill erosion. For that, we will run tests using a portable plot-scale (0.7 m2) rainfall simulator on Dystrophic Red Latosol using a rainfall intensity of 60 ± 5 mm h-1. We will study the following management systems: livestock loading in rotation Panicum Maximum cv. Mombaça pasture; continuous Brachiaria Decumbens pasture; soybean crop during summer and crop rotation during fall-winter; and integrated crop-livestock-forestry system alternating between a four-year Panicum Maximum cv. Massai pasture and a four-year soybean crop both associated with Eucalyptus production. The soil management systems have been established since 1993 to evaluate economic and agriculture efficiencies. Thereby, we look forward to providing not only economic advantages but also new reference values of soil erosion under integrated agricultural systems, helping to build resilience for food security. Our findings will also contribute to adequate land use, therefore, promoting soil and water conservation.

Climate change affects the global water cycle and has the potential to alter water availability for food-energy-water production and the ecosystems services on regional and local scales. In southeastern Brazil, the Cantareira Water Supply System reached unprecedented low levels in January 2015 compromising the water supply for the Metropolitan Region of São Paulo (MRSP). However, there is still few studies investigating the effects of climate change on water availability in this region. Here, we assess the influence of climate change on water availability in the Jaguari Basin, Southeastern Brazil using a modeling approach. This basin covers and area of about 1200 km2 and it is the main source of the Cantareira Water Supply System, responsible for providing water for about 7 million people in the MRSP. To evaluate climate change scenarios, we use the lumped conceptual HYMOD model on daily time step. This model was calibrated and evaluated using daily observed data of precipitation, evapotranspiration, and discharge for the period of 1990 to 2009. To evaluated climate change scenarios, we used data of an ensemble of 17 General Circulation Models (GCMs), downscaled by MarkSim GCM working off a 30 arc-second climate surface spatial resolution forced by two Representative Concentration Pathways (RCP): RCP 4.5 and RCP 8.5. These data were integrated into the HYMOD to projected scenarios (up to 2095) of water discharge. We find values of Nash-Sutcliffe Efficiency Coefficient (NSE) and Coefficient of Determination (R2) greater than 0.80 for the calibration and evaluation period. We also noticed an increase in the peak of runoff and a decrease and baseflow for both scenarios. Such changes reflect in a higher interannual variability, therefore, increasing the risk of drought and flood. In terms of Environmental Flow Requirement, the probability of exceedance Q90, reveal a clear pattern of decreasing, about 23% from 2010 to 2040, and reaching 28% by the end of the century. Our findings indicate that the water discharge could not be enough for the current and future water demand. Our results expose the fragility of the studied basin, presenting a technical and scientific information focusing on guiding the plans and strategies to deal with situations of water scarcity.