Predicting anoxia in the wet and dry periods of tropical semiarid reservoirs

Carneiro, Brenda Lara Duarte Souza; Rocha, Maria de Jesus Delmiro; Barros, Mário Ubirajara Gonçalves; Paulino, Walt Disney; Neto, Iran Eduardo Lima

doi:10.1016/j.jenvman.2022.116720

Cited by 9 publications

(9 citation statements)

References 32 publications

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“…There was a significant seasonal variation of water temperature. During the rainy season, temperatures are consistently higher than during the dry season, confirming a pattern also observed in other Brazilian semiarid reservoirs as reported by Carneiro et al (2023). The increase in water temperatures is a well-known contributor to intensified thermal stratification (Miao et al, 2023;Wei et al, 2022).…”

Section: Temperaturesupporting

confidence: 85%

Diel and seasonal mixing patterns and water quality dynamics in a multipurpose tropical semiarid reservoir

Rocha,

Barros,

Filho

et al. 2023

Preprint

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Eutrophication has become a recurrent concern in reservoirs worldwide. This problem is intensified in tropical semiarid regions, where the reservoirs have high seasonal and annual variability of water level and volume. Therefore, an extensive understanding of the diel variation of water quality key-parameters can help improve management of such reservoirs. This study focuses on Castanhão reservoir, the largest multipurpose dam in the Brazilian semiarid. Its main water uses are irrigation, fish farming, and human supply. The reservoir faced a decline in water quality due to a prolonged drought period. While previous research has predominantly emphasized the seasonal dynamics of thermal and chemical stratification, our investigation provides diel assessments of multiple water quality parameters, including nutrient concentrations and phytoplankton abundance. Our primary objective is to compare seasonal and diel variations in stratification and nutrient distribution within the reservoir. Key findings reveal a diel cycle of thermal stratification, primarily during dry season, driven by higher wind speeds. This is corroborated by a significant negative correlation between wind speed and the relative water column stability index. In contrast, during the rainy season, the reservoir experiences continuous thermal stratification due to inflowing water being warmer than the reservoir’s water temperature. Notably, a significant negative correlation between total phosphorus and chlorophyll-a, along with a two-fold increase of this nutrient throughout the day during the rainy season, underscores the influence of the phytoplankton community dynamics on the diel nutrient variation. Chemical stratification of dissolved oxygen occurred during dry and rainy seasons, indicating that even during the dry season, where there is no significant inflow, the internal nutrient loading can also significantly impact the water quality of a reservoir. This study advances the understanding of diel water quality dynamics in tropical semiarid reservoirs, shedding light on both climatic and anthropogenic influences on water resources.

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Section: Temperaturesupporting

confidence: 85%

Diel and seasonal mixing patterns and water quality dynamics in a multipurpose tropical semiarid reservoir

Rocha,

Barros,

Filho

et al. 2023

Preprint

Self Cite

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“…Overall, the results of this research are representative for other reservoirs with similar environmental conditions as the ones located in the Northeast region of Brazil, since they are all under the same meteorological-hydrological regimes: inflows limited to the wet season and stronger wind speeds in the dry period [69][70][71][72]. The marked stratification pattern observed in the wet season suggests that periods with high storage volumes probably have poor water quality.…”

Section: Discussionsupporting

confidence: 58%

“…This is confirmed by Rocha and Lima Neto [69,70], who noted peaks of external-phosphorus loads during the wet period, which favoured the reservoir's water-quality deterioration. On the other hand, Carneiro et al [72] found a more stable stratification pattern in the wet period, which was associated with very low dissolved-oxygen levels below the thermocline and internal-phosphorus release from the bottom sediment to the water column. However, it is important to stress that severe drought periods may present a complex behaviour as lower water volume indicates both mixing conditions, a state usually associated with better water quality, and less selfpurification efficiency, which is one of the circumstances indicative of poor water quality.…”

Section: Discussionmentioning

confidence: 96%

Two-Dimensional Modelling of the Mixing Patterns in a Tropical Semiarid Reservoir

et al. 2022

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Tropical semi-arid regions suffer with recurrent droughts and uncertain water availability, but a few research studies have been conducted to further understand those complexities and their relationships with reservoir hydrodynamics. This study assessed the hydrodynamic processes of a multiple-use reservoir located in the Brazilian semiarid region. The aim was to apply the CE-QUAL-W2 model to understand the lake’s thermal structure and its variabilities in time and space by using the Richardson’s number (Ri) as a reference. Meteorological patterns were also investigated. Results show that: (1) no significant changes were found by analysing the spatial variabilities of stratification; (2) seasonal changes were relevant as more robust stratification stability was observed in the wet period when water availability may be impacted by poor water quality; (3) from meteorological evaluations, rainfall showed a strong coefficient of determination with Ri (r² of 0.77); and (4) a threshold value of 60 mm in monthly precipitation was found as an indication of a stable stratification in the water column. Wind speed and water level partly influenced Ri’s variabilities, while low impact was noted for air temperature and inflow. These results can promote an improvement in water-resources management by linking rainfall regime and reservoir hydrodynamics.

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“…The high evaporation rate is a consequence of the high water temperatures (29 ± 2 ºC), typical of this region, with temperature contrasts between the upper and lower water layers of up to about 4ºC (Mesquita and Lima Neto, 2022; Rocha and Lima Neto, 2022a). This pronounced seasonal variation results in great variability of the stored volume and water quality in the reservoirs (Wiegand et al, 2021;Carneiro et al, 2023).…”

Section: Study Area and Methodologymentioning

confidence: 99%

Prediction of total phosphorus in reservoir cascade systems

Goes,

Barros,

Neto

2023

Environ Monit Assess

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Reservoir cascades have attracted the attention of scientists worldwide. The present study investigates the cascade of ve reservoirs (R1, R2, R3, R4 and R5) along a 192 km water channel system located in the State of Ceará, in the Brazilian semiarid region. This cascade system was implemented in 2012 to promote water availability and security to the capital of Ceará and the strategic industry and port complex of the region. However, these reservoirs have faced a progressive degradation of water quality, which has resulted in intense eutrophication and high water treatment costs. The study evaluates the dynamics of water quality from 2013 to 2021 along this reservoir cascade (from R1 to R5). The results revealed that water quality did not improve along the cascade system, differently from previous studies on reservoirs interconnected by natural rivers. This was attributed to the low water residence time and low capacity of pollutant removal along the man-made water channel system, as well as to the high internal phosphorus loads of the reservoirs. Multiple regression models involving the explanatory variables of total phosphorus, total nitrogen, chlorophyll-a, cyanobacteria, transparency, rainfall and volume from upstream reservoirs were obtained to determine total phosphorus concentration in downstream reservoirs, considering different combinations of reservoir pairs in the cascade and different time delays.A clear trend of R 2 decline with the distance between the upstream and downstream reservoirs was observed. For example, the R 2 -values for the correlations adjusted between R1 and R2 (48 km), R1 and R3 (172 km), R1 and R4 (178 km), and R1 and R5 (192 km) were 0.66, 0.32, 0.22, and 0.12, respectively. On the other hand, the adoption of time delays of the order of the cumulative residence times of the reservoirs promoted a signi cant improvement in the R 2 -values. For instance, the best correlation adjusted between R1 and R5 improved from R 2 = 0.12 to 0.69 by considering a time delay of 21 months. This suggests that previous data from upstream reservoirs can be used to predict current and future total phosphorus concentration in downstream reservoirs. The results from this study are important to better understand the spatiotemporal dynamics of water quality in reservoir cascade systems and thus improve water resources management, especially in drylands.

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Predicting anoxia in the wet and dry periods of tropical semiarid reservoirs

Cited by 9 publications

References 32 publications

Diel and seasonal mixing patterns and water quality dynamics in a multipurpose tropical semiarid reservoir

Diel and seasonal mixing patterns and water quality dynamics in a multipurpose tropical semiarid reservoir

Two-Dimensional Modelling of the Mixing Patterns in a Tropical Semiarid Reservoir

Prediction of total phosphorus in reservoir cascade systems

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