Kamila Almeida dos Santos

Understanding cyanobacterial dominance in tropical reservoirs is crucial for water management. This study examined the dynamics of water quality in the João Leite Reservoir, situated in the Brazilian Cerrado, utilising 30 months of monitoring data from five sites. Physical, chemical, and biological parameters, including fluorometric chlorophyll-a, using multivariate statistics (Cluster Analysis, Principal Component Analysis, PCA; Canonical Correlation Analysis, CCA), were analysed alongside the Trophic State Index (TSI). Results showed temporal variations exceeded spatial differences. Cyanobacteria were dominant despite generally low nutrient levels and an oligotrophic TSI classification. Principal Component Analysis revealed that temperature is strongly associated with cyanobacterial density. However, Canonical Correspondence Analysis and correlations revealed limited direct statistical influence of measured physicochemical parameters, including nutrients, on cyanobacterial abundance. Findings suggest that in this warm, tropical system, high temperatures combined with stable hydrodynamics, resulting from long hydraulic retention times (>180 days), likely facilitate cyanobacterial success, overriding direct nutrient limitation.

Effective water resource management and risk mitigation in urban environments require an accurate understanding of river flow dynamics. Traditionally, river discharge estimation relies on the rating curve method, which, despite being simple and low-cost, presents significant limitations in complex channels or under transient flow regimes. Aiming for greater accuracy in discharge estimates, this study employed a one-dimensional hydraulic model based on the Standard Step Method for gradually varied flows. High-quality in situ data, including detailed bathymetric surveys and water level measurements, were used for model calibration and validation. Discharge uncertainty was quantified through the estimation of hydraulic parameters (S₀ and n), comparing the Bayesian approaches GLUE and DREAM. The final uncertainty ranges in discharge estimates (Relative Error) using the DREAM method varied between 6.75% and 7.34%, while the GLUE method presented ranges between 7.31% and 8.64%. The DREAM method demonstrated superior performance, including faster processing speed. It was also observed that model accuracy tends to improve with decreasing water surface elevation, indicating the need for longer data collection intervals during extreme events.

Understanding cyanobacterial dominance in tropical reservoirs is crucial for water management. This study investigated water quality dynamics in the João Leite Reservoir, Brazilian Cerrado, using 30 months of monitoring data from five sites. Physical, chemical, and biological parameters, including fluorometric chlorophyll-a and phycocyanin, were analysed alongside the Trophic State Index (TSI) using multivariate statistics (PCA, CCA). Results showed temporal variations exceeded spatial differences. Cyanobacteria were dominant despite generally low nutrient levels and an oligotrophic TSI classification. Principal Component Analysis identified temperature as strongly associated with cyanobacterial density. However, Canonical Correspondence Analysis and correlastions revealed limited direct statistical influence of measured physicochemical parameters, including nutrients, on cyanobacterial abundance. Findings suggest that in this warm, tropical system, high temperatures combined with stable hydrodynamics due to long hydraulic retention (>180 days) likely facilitate cyanobacterial success, overriding direct nutrient limitation.