ABSTRACT
Water resources planning and management are dependable on an adequate integration of physical, chemical, biological, and socio-economic realities of multiple water users. The dynamic of water quantity and quality in rivers are affected by several conditions, such as land use, soil characteristics, and meteorological and hydrological processes. Among these, the presence of hydraulic structures, such as dams and reservoirs, are often responsible for hydrodynamic and geomorphological alterations, leading to impacts on water quality and ecological behavior. In this context, this study presents the combination of a solution of the one-dimensional flow and transport and fate of contaminants in rivers (SihQual model) with a continuously stirred tank reactor (CSTR) to represent the reservoir. The first model solves the hydrodynamic and water quality equations under unsteady state, while the second approach considers the reservoir as a complete mixed system with inputs that vary over time. The main goal is to provide an integrated analysis for planning and management in a watershed where water has multiple purposes of use. The case study is the Iguaçu watershed, where the main river is affected by several dams for hydroelectric power generation. The simulation covers 542 km of the Iguaçu River and the Foz do Areia reservoir (flooded area of 139.5 km2), using data from 12 monitoring stations. The region also has issues of water quality impairment and water scarcity events due to deforestation, and urban and agricultural activities, exemplifying challenges throughout the world. Results show that the integrated models can reproduce the expected variability in different systems, although calibration challenges arise in multiscale modeling. The data indicate that, overall, the lentic environment is able to deplete organic matter and phosphorus, in comparison to levels in the fluvial flow. Nonetheless, experiments show that the river-reservoir system may be highly sensible to external and internal changes, such as water availability throughout time and pollution from the main tributary, as well as outlet discharges and transformation processes in the water column, leading to a possibility of critical events. Therefore, the study highlights how planning and managing actions in the watershed can benefit from an integrated river-reservoir analysis.
Subject(s)
Rivers , Water Pollutants, Chemical , Rivers/chemistry , Water Quality , Models, Theoretical , Hydrology , Phosphorus/analysis , Environmental Monitoring/methods , Water Pollutants, Chemical/analysisABSTRACT
Recent water resources planning and management strategies state that the concepts of risk and variable inputs should be appraised in order to comply with multiple conditions. This becomes evident especially in environments with diverse uses of water, land use and climate change. In such a context, modelling of discharges and concentrations in rivers are valuable strategies to predict different scenarios. This research proposes an integrated analysis for modelling of flow and contaminant transport in rivers, based on hydrodynamics, time series, and water quality simulations. The first module estimates water volume and velocity, that have direct impact in pollutants transport; time series of concentrations are generated as synthetic pollutographs, using techniques based on flow conditions, time and statistical factors of a historical monitoring dataset - the objective is to match temporal scales of boundary conditions, since water quality data is usually available as irregular samples; the third module solves the advection-dispersion-reaction equation, exploring the different synthetic series as input. Results evidence that the input pollutograph, usually not explored in similar studies, may have a significant role in simulations for transport of substance in rivers under unsteady state; as consequence, corroborate with better estimates for planning strategies where temporal dynamic is relevant. The contributions lay the basis for further assessment of riverine systems linked to watershed dynamics, with multiple scenarios of data availability and input conditions.
Subject(s)
Models, Theoretical , Water Quality , Climate Change , Rivers , Water ResourcesABSTRACT
Mudanças na temperatura da água e na dinâmica de estratificação térmica podem causar efeitos negativos sobre os processos físicos, químicos e biológicos de reservatórios. A variação da temperatura afeta a densidade da água e, como consequência, altera os processos de transporte. Um modelo unidimensional de transferência de calor é utilizado para simular a temperatura do reservatório do Rio Verde, localizado na região metropolitana de Curitiba, Estado do Paraná. Na solução da equação, usou-se o método de diferenças finitas. O modelo foi calibrado e validado por meio dos dados de dois meses: julho de 2009 e março de 2010. Os resultados mostram uma boa concordância entre os valores simulados e observados. Esses resultados ainda permitem avaliar as relações da profundidade da termoclina com a radiação solar e a velocidade do vento.
Changes in the water temperature and in the thermal stratification dynamics can be responsible for negative effects on physical, chemical and biological processes of reservoirs. The temperature variation affects the water density and, consequently, alters the transport processes. A one-dimensional model of thermal evolution is used to simulate the temperature of Rio Verde reservoir, located in the Curitiba metropolitan area, Paraná state, Brazil. The finite difference method was employed for the numerical solution of the equation. The model was calibrated and validated by means of the data from two different months: July 2009 and March 2010. The results show a good agreement between simulated and observed values. These results still allow evaluating the relationships between the depth of the thermocline with solar radiation and wind speed.
