Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista (UNESP), Programa de Pós-Graduação em Agronomia, Ciência do Solo, Via de Acesso Prof. Paulo Donato Castellane, s/n, Jaboticabal, SP 14884-900, Brazil; Polo Regional Centro Norte, Departamento de Descentralização do Desenvolvimento - APTA, Secretaria de Agricultura e Abastecimento - SAA, Rodovia Washington Luis, Km 371, s/n, Pindorama, SP 15830-000, Brazil; POLUS-Grupo de Política de Uso do Solo, Universidade Estadual Paulista (UNESP), Via de Acesso Prof. Paulo Donato Castellane, s/n, Jaboticabal, SP 14884-900, Brazil.
Polo Regional Centro Norte, Departamento de Descentralização do Desenvolvimento - APTA, Secretaria de Agricultura e Abastecimento - SAA, Rodovia Washington Luis, Km 371, s/n, Pindorama, SP 15830-000, Brazil.
Sci Total Environ. 2021 Mar 25;762:144511. doi: 10.1016/j.scitotenv.2020.144511. Epub 2020 Dec 16.
The integration of internal (e.g., stratification) and external (e.g., pollution) factors on a comprehensive assessment of reservoir water quality determines the success of ecosystem restoration initiatives and aids watershed management. However, integrated analyses are scarcer than studies addressing factors separately. Integration is likely more efficient in studies of small well-characterized (experimental) reservoir watersheds, because the isolation of factor contributions is presumably clearer. But those studies are uncommon. This work describes the water quality of two small 5.5 m-deep reservoirs (MD-Main and VD-Voçoroca dams) located in Pindorama Experimental Center, state of São Paulo, Brazil, considering the interplay between reservoir dimension, seasonal thermal stratification, chemical gradients, erosive rainfall events, presence of natural biofilters, and land uses and landscape patterns around the reservoirs and within the contributing watersheds. The monitoring of agricultural activities and water quality parameters occurred in October 2018-July 2019. A 4 °C thermal stratification occurred in October (difference between surface and bottom water temperature), which decreased until disappearance in January (VD) or April (MD). The longer stratification period of MD was justified by its larger area relative to VD (≈10×). Thermal stratification triggered hypoxia at the bottom of both reservoirs (DO ≈ 1 mg/L), more prolonged and severe in MD. Hypoxia activated Ec and TDS peaks in January likely explained by bottom-sediment nutrient releases, presumably phosphorus. The Ec peak reached 560 μS/cm in MD and 290 μS/cm in VD. The smaller VD peak was probably explained by the action of macrophytes. In March, a 240 NTU turbidity peak occurred in MD, caused by precedent erosive rainfall and the lack of vegetation protection alongside the south border. As expected, the study accomplished clear isolation of factor contributions, verified by Factor and Cluster analyses. Our results can subsidize studies on larger reservoir watersheds requiring restoration, where the isolation of factors is more challenging.
综合评估水库水质的内部（如分层）和外部（如污染）因素决定了生态系统恢复计划的成功，并有助于流域管理。然而，综合分析比分别研究因素的研究更为少见。在小而特征明显（实验性）的水库流域的研究中，综合分析可能更有效，因为可以更清楚地隔离因素的贡献。但这些研究并不常见。本工作描述了位于巴西圣保罗州平多兰萨实验中心的两个 5.5 米深的水库（MD-主水库和 VD-沃科罗卡大坝）的水质情况，考虑了水库尺寸、季节性热分层、化学梯度、侵蚀性降雨事件、天然生物滤池的存在以及水库周围和集水区内的土地利用和景观格局之间的相互作用。2018 年 10 月至 2019 年 7 月对农业活动和水质参数进行了监测。10 月出现了 4°C 的热分层（水面和底部水温之间的差异），直到 1 月（VD）或 4 月（MD）才消失。MD 的分层期较长，这是因为其面积相对于 VD 较大（约 10 倍）。热分层在两个水库的底部引发了缺氧（DO≈1mg/L），MD 的缺氧更为持久和严重。缺氧可能导致 1 月底沉积物中养分释放，从而激活 Ec 和 TDS 峰值，可能是磷。MD 的 Ec 峰值达到 560μS/cm，VD 的 Ec 峰值达到 290μS/cm。VD 较小的峰值可能是由大型植物的作用造成的。3 月，MD 出现了 240NTU 的浊度峰值，这是由先前的侵蚀性降雨和南部边界缺乏植被保护造成的。正如预期的那样，通过因子和聚类分析，该研究清楚地隔离了因子的贡献。我们的结果可以为需要恢复的更大水库流域的研究提供依据，在这些研究中，隔离因子更具挑战性。
