Avaliação da hidrodinâmica do reservatório Edson Queiroz, no Ceará

Abstract

Water scarcity in the semi-arid region of Ceará occurs in both quantity and quality, making reservoir monitoring a challenge, as the region's climatic conditions directly affect the hydrodynamics of reservoirs. This study aimed to analyze temperature, hydraulic residence time, horizontal and vertical velocities, and the phosphorus decay coefficient (k), modeled using the two-dimensional hydrodynamic model CE-QUAL-W2. The study area was the Edson Queiroz reservoir, located in the municipality of Santa Quitéria, with a storage capacity of 240 million m³. Data provided by FUNCEME were calibrated, and after modeling, time series of the parameters were created for the period between 2016 and 2021. For seasonality analysis, the accumulated precipitation of each year was considered, selecting 2018 due to its lower standard deviation relative to the average. The results indicated that the interannual mean temperature was 27.31 ºC. The average hydraulic residence time was 559.03 days, increasing during the dry period and showing sharp declines during the rainy period, reflecting the influence of reservoir inflow. The average horizontal velocity was 0.012 m/s, while the vertical velocity was 2.1594 × 10⁻u m/s, indicating a predominantly horizontal flow. The phosphorus decay coefficient showed significant variation, with values ranging from 0.1082 to 34.0625 year⁻¹, with an average of 0.2247 year⁻¹. In the seasonal evaluation of 2018, the average temperature was 27.01 ºC in the rainy season and 26.33 ºC in the dry season. The rainy season showed greater thermal variability, with temperature gradients observed in March, April, and May. The average hydraulic residence time was 333.49 days in the rainy period and 501.07 days in the dry period, reflecting the influence of water inflow into the reservoir. The average horizontal velocity was 0.01317 m/s during the rainy period and 0.01390 m/s in the dry period. Vertical circulation showed average values of 2.4391 × 10⁻u m/s in the rainy period and 2.34658 × 10⁻u m/s in the dry period. The phosphorus decay coefficient was 0.29 year⁻¹ in the rainy period and 0.19 year⁻¹ in the dry period, indicating greater efficiency in nutrient removal during the rainy season. For model validation, measured and simulated temperatures were compared at segments 83 and 53, with variations of 0.95 ºC and 1.31 ºC, respectively, indicating a good fit of the model to real conditions. It is concluded that environmental and seasonal variables significantly influence hydrodynamic patterns, highlighting the importance of mathematical modeling in water resource management in the semi-arid region.