cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.11839425
title: Scenarios of climate change effects in water availability within the patos Lagoon’s Basin

description: ABSTRACT The decision-making processes involving water resources in Brazil and in neighboring countries have been based solely on analyses of the historical behavior of hydroclimatological variables. However, this may lead to inappropriate strategies in regards to the use of natural resources, since the impact of future climate change may significantly affect the availability of water resources. This study proposes an analysis of the variation in water availability of basins within the Patos Lagoon contribution area, which may be a consequence of climatic changes predicted by CMIP5 (Coupled Model Intercomparison Project Phase 5) models, published in the most recent International Panel on Climate Change (IPCC) report. Two 30-year periods were simulated, from 2006 to 2035 and from 2051 to 2080, through the MGB-IPH hydrological model, considering two extreme greenhouse gas scenarios and twenty climate change models. A tendency of increase of the flows was verified in the simulated basin, since over 60% of the simulations indicated some percentage of average flow increase across all discretized modeling units. The analysis of the simulation results indicated that the data from climatic models HadGEM2-ES and GFDL-CM3 used as input in the hydrological model are the ones that respectively provide upper and lower flow thresholds for the ensembled simulations. A joint evaluation of the results generated by these two models, associated with the scenario of high greenhouse gas emissions, is capable of covering extreme flow scenarios making predictions considering climate change in the Patos Lagoon’s basin. Whereas the results provided by bcc-csm1, BNU-ESM and CNRM-CM5 are similar to the median of the ensemble of simulations generated by all models evaluated in this research. In addition, the northernmost region of the study area was identified as having the highest sensitivity to climate change, as projected by global models of CMIP5 published in AR5.
DOI: 10.6084/m9.figshare.11839410
title: Effect of the reduction of the outflow restriction discharge from the Xingó dam in water salinity in the lower stretch of the São Francisco River

description: ABSTRACT Among the water quality parameters subjected to changes in river flow variations, salinity stands out for being intrinsically associated to ecosystem quality. Nonetheless, salinization can cause irreversible damage to the structure and functions of aquatic communities. This work evaluated the effect of successive reductions of outflow discharges from Xingó dam in water salinity in the lower stretch of the São Francisco River, Brazil. Salinity was analysed downstream of the dam, in addition to the relation between discharge reductions and salinity levels, as well as the spatial evolution of salinity in function of the distance of the sampling points from the river mouth. Secondary water quality data from 17 monitoring points were analysed, moreover, field samples and laboratory analyses were performed. With the reductions of outflow discharges, that started in 2013, there was a considerable increase in salinity in the sampling point located 9 km far from the river mouth, and with the continuation of discharge reductions, points that are farther away from the river mouth also presented high salinity values, both in the bottom and on the surface. This study indicates salinity values above the limits of fresh water (0.5 ‰), established by the CONAMA Resolution 357, for human consumption.
DOI: 10.6084/m9.figshare.11839410.v1
title: Effect of the reduction of the outflow restriction discharge from the Xingó dam in water salinity in the lower stretch of the São Francisco River

description: ABSTRACT Among the water quality parameters subjected to changes in river flow variations, salinity stands out for being intrinsically associated to ecosystem quality. Nonetheless, salinization can cause irreversible damage to the structure and functions of aquatic communities. This work evaluated the effect of successive reductions of outflow discharges from Xingó dam in water salinity in the lower stretch of the São Francisco River, Brazil. Salinity was analysed downstream of the dam, in addition to the relation between discharge reductions and salinity levels, as well as the spatial evolution of salinity in function of the distance of the sampling points from the river mouth. Secondary water quality data from 17 monitoring points were analysed, moreover, field samples and laboratory analyses were performed. With the reductions of outflow discharges, that started in 2013, there was a considerable increase in salinity in the sampling point located 9 km far from the river mouth, and with the continuation of discharge reductions, points that are farther away from the river mouth also presented high salinity values, both in the bottom and on the surface. This study indicates salinity values above the limits of fresh water (0.5 ‰), established by the CONAMA Resolution 357, for human consumption.
DOI: 10.6084/m9.figshare.11965869
title: Assessing two precipitation data sources at basins of special interest to hydropower production in Brazil

description: ABSTRACT Accurate estimates of precipitation amounts are necessary to evaluate river flows, assess water-related risks (floods and drought) and quantify water availability for a broad range of water uses, such as water supply, agriculture, navigation and energy production. Especially in the context of operations in the Brazilian electricity sector, where the electrical system is essentially hydrothermal and more than 65% of its production comes from hydroelectric generation, real-time observed precipitation plays a key role as a primary input for hydrological models and river flow forecasting. It is thus crucial to build knowledge on and quantify river basin precipitation and its uncertainties. In this paper, we evaluate two sources of real-time (or near real-time) precipitation data, the TRMM-MERGE dataset from the CPETC and the CPC dataset, distributed by NOAA. Our assessment is based on 41 river basins in South America and covers the period 1997-2017. We investigated differences for different time resolutions (daily, monthly and annual precipitation) and their impact on the simulation of streamflows. Substantial differences were found between the two data sources, which seem to be amplified in the second decade. A spatial trend was found towards higher TRMM-MERGE precipitation values than CPC values when moving from north and west in the study area. We also found evidence that differences in precipitation propagate to simulated flows, with large percent differences in precipitation resulting in even larger percent differences in streamflow.
DOI: 10.6084/m9.figshare.11965869.v1
title: Assessing two precipitation data sources at basins of special interest to hydropower production in Brazil

description: ABSTRACT Accurate estimates of precipitation amounts are necessary to evaluate river flows, assess water-related risks (floods and drought) and quantify water availability for a broad range of water uses, such as water supply, agriculture, navigation and energy production. Especially in the context of operations in the Brazilian electricity sector, where the electrical system is essentially hydrothermal and more than 65% of its production comes from hydroelectric generation, real-time observed precipitation plays a key role as a primary input for hydrological models and river flow forecasting. It is thus crucial to build knowledge on and quantify river basin precipitation and its uncertainties. In this paper, we evaluate two sources of real-time (or near real-time) precipitation data, the TRMM-MERGE dataset from the CPETC and the CPC dataset, distributed by NOAA. Our assessment is based on 41 river basins in South America and covers the period 1997-2017. We investigated differences for different time resolutions (daily, monthly and annual precipitation) and their impact on the simulation of streamflows. Substantial differences were found between the two data sources, which seem to be amplified in the second decade. A spatial trend was found towards higher TRMM-MERGE precipitation values than CPC values when moving from north and west in the study area. We also found evidence that differences in precipitation propagate to simulated flows, with large percent differences in precipitation resulting in even larger percent differences in streamflow.
DOI: 10.6084/m9.figshare.12056532
title: Start position of a sloping hydraulic jump

description: ABSTRACT Although sloping hydraulic jumps are frequent in energy dissipators, there are few studies regarding this type of phenomenon. Since the jump is accompanied by violent impacts and sudden variations of velocity and pressure, it is important to know the region where the phenomenon will occur, in order to make a safe and economic design possible. In this paper, a methodology for the determination of the start position of the sloping jump along a Creager spillway is introduced. It was verified that this position is a function of both the incident Froude number and the submergence factor.
DOI: 10.6084/m9.figshare.12056532.v1
title: Start position of a sloping hydraulic jump

description: ABSTRACT Although sloping hydraulic jumps are frequent in energy dissipators, there are few studies regarding this type of phenomenon. Since the jump is accompanied by violent impacts and sudden variations of velocity and pressure, it is important to know the region where the phenomenon will occur, in order to make a safe and economic design possible. In this paper, a methodology for the determination of the start position of the sloping jump along a Creager spillway is introduced. It was verified that this position is a function of both the incident Froude number and the submergence factor.
DOI: 10.6084/m9.figshare.12056505
title: Impact of large reservoirs on simulated discharges of Brazilian rivers

description: ABSTRACT Tens of thousands of dams were built around the world to reduce flood risks, produce energy, and maximize benefits of limited freshwater resources. In Brazil, the main and largest reservoirs are related to hydropower plants. Improving the understanding of reservoir dynamics is important not only to evaluate their impact in the flow regime of Brazilian rivers, but also to simulate the combined effect of constructing new dams and potential alterations under future climatic conditions. Here, we analyze how an ideal representation of reservoirs in terms of forced discharge would improve a previously calibrated hydrological model under the Brazilian domain. We forced the continental-scale version of the MGB model on observed reservoir outflows from 109 hydropower dams, which are part of the Brazilian National Interconnected System controlled by the National Electrical System Operator. Model simulated flows were replaced by the reservoir outflows in all dam locations and were compared to the original discharge in downstream gauges. The forced discharge simulation presented a mean improvement for Kling-Gupta Efficiency of 21%, when compared to the original model (naturalized flow). This analysis is a preliminary step towards an explicit representation of the reservoirs in the model, what will be conducted in a future study.
DOI: 10.6084/m9.figshare.12056505.v1
title: Impact of large reservoirs on simulated discharges of Brazilian rivers

description: ABSTRACT Tens of thousands of dams were built around the world to reduce flood risks, produce energy, and maximize benefits of limited freshwater resources. In Brazil, the main and largest reservoirs are related to hydropower plants. Improving the understanding of reservoir dynamics is important not only to evaluate their impact in the flow regime of Brazilian rivers, but also to simulate the combined effect of constructing new dams and potential alterations under future climatic conditions. Here, we analyze how an ideal representation of reservoirs in terms of forced discharge would improve a previously calibrated hydrological model under the Brazilian domain. We forced the continental-scale version of the MGB model on observed reservoir outflows from 109 hydropower dams, which are part of the Brazilian National Interconnected System controlled by the National Electrical System Operator. Model simulated flows were replaced by the reservoir outflows in all dam locations and were compared to the original discharge in downstream gauges. The forced discharge simulation presented a mean improvement for Kling-Gupta Efficiency of 21%, when compared to the original model (naturalized flow). This analysis is a preliminary step towards an explicit representation of the reservoirs in the model, what will be conducted in a future study.
DOI: 10.6084/m9.figshare.12056541
title: Monitoring water content changes in a soil profile with TDR-probes at just three depths - How well does it work?

description: ABSTRACT TDR-probes are widely used to monitor water content changes in a soil profile (ΔW). Frequently, probes are placed at just three depths. This raises the question how well such a setup can trace the true ΔW. To answer it we used a 2 m deep high precision weighing lysimeter in which TDR-probes are installed horizontally at 20, 60 and 120 cm depth (one per depth). ΔW-data collected by weighing the lysimeter vessel were taken as the true values to which ΔW-data determined with the TDR-probes were compared. We obtained the following results: There is a time delay in the response of the TDR-probes to precipitation, evaporation, transpiration or drainage, because a wetting or drying front must first reach them. Also, the TDR-data are more or less point measurements which are then extrapolated to a larger soil volume. This frequently leads to errors. For these reasons TDR-probes at just three depths cannot provide reliable data on short term (e.g. daily) changes in soil water content due to the above processes. For longer periods (e.g. a week) the data are better, but still not accurate enough for serious scientific studies.
DOI: 10.6084/m9.figshare.12056541.v1
title: Monitoring water content changes in a soil profile with TDR-probes at just three depths - How well does it work?

description: ABSTRACT TDR-probes are widely used to monitor water content changes in a soil profile (ΔW). Frequently, probes are placed at just three depths. This raises the question how well such a setup can trace the true ΔW. To answer it we used a 2 m deep high precision weighing lysimeter in which TDR-probes are installed horizontally at 20, 60 and 120 cm depth (one per depth). ΔW-data collected by weighing the lysimeter vessel were taken as the true values to which ΔW-data determined with the TDR-probes were compared. We obtained the following results: There is a time delay in the response of the TDR-probes to precipitation, evaporation, transpiration or drainage, because a wetting or drying front must first reach them. Also, the TDR-data are more or less point measurements which are then extrapolated to a larger soil volume. This frequently leads to errors. For these reasons TDR-probes at just three depths cannot provide reliable data on short term (e.g. daily) changes in soil water content due to the above processes. For longer periods (e.g. a week) the data are better, but still not accurate enough for serious scientific studies.
DOI: 10.6084/m9.figshare.12171237
title: Numerical and experimental models applied to an ogee crest spillway and roller bucket stilling basin

description: ABSTRACT Traditionally, reduced physical models are used to allow control, instrumentation and experimental evaluation of flow. More recently, computational fluid dynamics (CFD) has emerged as a tool that allows numerical modeling of flows and can complement the information provided by the physical model. The objective this paper is to validate the CFD tool in reproducing the flow through an ogee crest spillway with a roller bucket stilling basin. This validation was performed with the data from a reduced scale experiment in which measurements were made of the position of the water free surface and of the pressure loads in the spillway profile. It was verified that the CFD tool is suitable for the study of this type of flow, being able to reproduce the experimental results. In the execution of the numerical simulations, special attention was given to the influence of the mesh on the results. An important influence of the mesh was observed in some results, which shows the importance a sensitivity analysis of this parameter when performing CFD simulations. The obtained results offer the prospect of using CFD as a supporting tool for the design of spillways and stilling basins.
DOI: 10.6084/m9.figshare.12171237.v1
title: Numerical and experimental models applied to an ogee crest spillway and roller bucket stilling basin

description: ABSTRACT Traditionally, reduced physical models are used to allow control, instrumentation and experimental evaluation of flow. More recently, computational fluid dynamics (CFD) has emerged as a tool that allows numerical modeling of flows and can complement the information provided by the physical model. The objective this paper is to validate the CFD tool in reproducing the flow through an ogee crest spillway with a roller bucket stilling basin. This validation was performed with the data from a reduced scale experiment in which measurements were made of the position of the water free surface and of the pressure loads in the spillway profile. It was verified that the CFD tool is suitable for the study of this type of flow, being able to reproduce the experimental results. In the execution of the numerical simulations, special attention was given to the influence of the mesh on the results. An important influence of the mesh was observed in some results, which shows the importance a sensitivity analysis of this parameter when performing CFD simulations. The obtained results offer the prospect of using CFD as a supporting tool for the design of spillways and stilling basins.
DOI: 10.6084/m9.figshare.12171231
title: Scenarios of water quality management in watershed with distributed spatio-temporal simulation

description: ABSTRACT The implementation of National Water Resources Policy instruments depends on detailed information in space and time, on a large scale, within the river basin. This research aims to evaluate scenarios to support water quality management in watershed by modelling with spatio-temporal discretization distributed in a small spatial dimension. The SWAT hydrological model was applied in the Itajai river basin. This hydrographic basin with 15,000 km2 was discretized in 2,103 hydrological response units (HRUs). The model input data for each HRU were fed in, from the quantitative and qualitative aspects. The time series of water quality was obtained in non-systematic monitoring from different sources, such as water supply companies and potential polluting companies, among others. The model calibration and validation were performed, presenting adequate results for both the quantitative and qualitative processes. The scenarios corresponding to current and evolutionary situations of pollutant contribution for four water quality parameters (biochemical oxygen demand, total phosphorus, total nitrogen and thermotolerant coliforms) were analysed. The results are expressed as the mean, median, non-exponential frequency of 80% and reference flow, discussing the statistical index that best represents the pollutant concentrations in the bodies of water. The simulations show that the measures proposed for the water quality management of the basin promote a significant reduction in pollutant concentrations in comparison to the critical scenario. According to the results, it can be affirmed that the discretization of the basin in small contribution areas generates greater results precision of the model. The daily and distributed data in the basin provide localized information, according to the basin ortho coding, supporting the decision in order to support the management of water resources, contributing to the implementation process of the framework of surface water courses in the basin, as well as serving as a generic model for other purposes.
DOI: 10.6084/m9.figshare.12171231.v1
title: Scenarios of water quality management in watershed with distributed spatio-temporal simulation

description: ABSTRACT The implementation of National Water Resources Policy instruments depends on detailed information in space and time, on a large scale, within the river basin. This research aims to evaluate scenarios to support water quality management in watershed by modelling with spatio-temporal discretization distributed in a small spatial dimension. The SWAT hydrological model was applied in the Itajai river basin. This hydrographic basin with 15,000 km2 was discretized in 2,103 hydrological response units (HRUs). The model input data for each HRU were fed in, from the quantitative and qualitative aspects. The time series of water quality was obtained in non-systematic monitoring from different sources, such as water supply companies and potential polluting companies, among others. The model calibration and validation were performed, presenting adequate results for both the quantitative and qualitative processes. The scenarios corresponding to current and evolutionary situations of pollutant contribution for four water quality parameters (biochemical oxygen demand, total phosphorus, total nitrogen and thermotolerant coliforms) were analysed. The results are expressed as the mean, median, non-exponential frequency of 80% and reference flow, discussing the statistical index that best represents the pollutant concentrations in the bodies of water. The simulations show that the measures proposed for the water quality management of the basin promote a significant reduction in pollutant concentrations in comparison to the critical scenario. According to the results, it can be affirmed that the discretization of the basin in small contribution areas generates greater results precision of the model. The daily and distributed data in the basin provide localized information, according to the basin ortho coding, supporting the decision in order to support the management of water resources, contributing to the implementation process of the framework of surface water courses in the basin, as well as serving as a generic model for other purposes.