ABSTRACT
Surface sediment concentration (SSC) is linked to several problems related to water quality and its monitoring is costly because of the required fieldwork and laboratory analyses. Thus, sediment measurements are often sporadic, punctual, and performed during a short period. Orbital remote sensing allows the monitoring of SSC along the river channel permitting continuous and spatial information. This work had two objectives: (1) to model the surface concentration of sediments in the main channel of the Doce river using data from Multispectral Instrument (MSI)/Sentinel 2 and Operational Land Imager (OLI)/Landsat 8 satellite sensors; and (2) to compare different linear modeling approaches to select the best variables for SSC monitoring. For comparison with actual field data, we used mean SSC measurements in 14 sediment gauge stations from 2013 to 2020. Reflectance data of the MSI/Sentinel 2 and OLI/Landsat 8 satellites bands and spectral indices related to the monitoring of water resources were used as explanatory variables. Simple and multiple linear regression models (SLR and MLR), least absolute shrinkage and selection operator (LASSO), and Elastic Net regression were used to predict the SSC. The near-infrared band images from both MSI/Sentinel 2 and OLI/Landsat 8 satellites showed a strong linear relationship with the SSC. Multiple linear regression, LASSO and Elastic Net regressions showed good performance for SSC prediction. Sediment flow maps show an SSC reduction in the Doce river channel in recent years, indicating that part of the material from the Fundão tailings dam rupture may have been transported through sediment resuspension and transport processes.
Subject(s)
Environmental Monitoring , Rivers , Environmental Monitoring/methods , Remote Sensing Technology , Water QualityABSTRACT
Climate change and the intensification of anthropogenic activities in watersheds have been substantially changing the streamflow regime, which is a problem for water resource managers. This study assesses the influence of the changes in land use and land cover and rainfall on the streamflow regime. This study also models the pattern of these streamflows according to the rainfall and land use and land cover in the Santo Antônio River watershed, located in the transitioning region of the Brazilian Biomes Atlantic Forest and Cerrado. To assess the dynamic relationship between land use and land cover and the streamflow regime, five classes of land use and land cover were used. To characterize the hydrological pattern, data from six streamflow gauges and 24 rainfall gauges that influence the study area were used. Multiple regression models were adjusted to estimate streamflow using the explanatory variables rainfall and land use and land cover. As result, a direct relationship was found, as the decrease in streamflow in some drainage areas was influenced by the decrease in rainfall over the base period. The relationship between land use and land cover and streamflow was not significant. The reductions in the streamflow regimes over the years in the watershed were influenced by reductions in annual rainfall, which reduced about 19% while the water withdrawals from 2003 to 2014 increased 2350%. The results found in this study are useful to the water managers since they can estimate streamflow in any part of the studied river through rainfall and land use and land cover data. This helps to reduce the risks associated with the water allocation process.
Subject(s)
Environmental Monitoring , Models, Theoretical , Brazil , Ecosystem , ForestsABSTRACT
The objective of this work was to evaluate the efficiency of a hydrocyclone to separate sand in irrigation water. To do this, it an experiment was conducted where the hydrocyclone was operated with pressures and discharge that varied from 10 to 60 kPa and from 1,159.90 L h-1 to 2,603.60 L h-1, respectively. During the tests, the sand concentration in suspension varied from 2.81 g L-1 to 7.01 g L-1. The results showed that the best efficiency was obtained with pressure differentials of 10 and 30 kPa, with cut size (d70) of 50 µm.
Neste trabalho, o principal objetivo foi avaliar a capacidade de um hidrociclone em reter areia suspensa na água de irrigação. O hidrociclone operou com diferenciais de pressão que variaram de 10 a 60 kPa e vazões entre 1.159,90 a 2.603,60 L h-1. A concentração de areia na suspensão variou de 2,81 a 7,01 g L-1. Os resultados mostraram que as melhores eficiências de remoção foram obtidas para os diferenciais de pressão de 10 e 30 kPa, e diâmetros de corte (d70) de 50 µm.
