This study aims to analyze the factors affecting algal growth due to hydrologic and hydrodynamic changes resulting from eight weir constructions along a length of 207 km on the Nakdong River. Nutrients for algal growth, light intensity, water temperature, and hydrodynamic conditions were examined to study their relationships with algal blooms. A three-dimensional hydrodynamic and water quality model was calibrated based on data from 2006 to 2008 and verified against data from 2013 to 2015. Four statistics (i.e., R², ME, Pbias, and CF) were used for the model performance assessment. Changes in algal bloom were not significant in the upper stream area because the nutrient level for algal growth was insufficient compared to that at other locations. On the other hand, as the nutrient concentration increased in the middle stream area, algal blooms increased significantly. The upper and middle streams showed increases in algal growth after the construction of weirs. However, hypereutrophic downstream area locations showed contrasting results, showing an overall reduction in algal growth after the construction of weirs, except for winter, which showed the largest increase in hydraulic residence time. These results seem to have positive and negative effects on algal blooms due to the construction of weirs. The negative effects seem to be greater in hypereutrophic areas because of the decreased average light effect as a result of increased water depth created through the weir constructions, playing a dominant role over the level of nutrients. The impacts of the construction of weirs on the occurrence of algae in the Nakdong River were as follows: 1) As the hydraulic residence time increased, the algal bloom increased where the nutrients were sufficient; 2) when the nutrients were more than sufficient, the average light availability became the dominant factor for algal growth; 3) the temperature effect was not a significant algal-growth-limiting factor for hydrodynamic changes in the river. However, these results have limitations in terms of the model and data accuracy. In order to use them for water resource management, additional field experiments are required for confirmation and verification.

这项研究旨在分析因洛东河沿207公里长的8个堰构造而导致的因水文和水动力变化而影响藻类生长的因素。检查了藻类生长，光强度，水温和水动力条件的养分，以研究它们与藻华的关系。基于2006年至2008年的数据对三维水动力和水质模型进行了校准，并对照2013年至2015年的数据进行了验证。四个统计数据（即R ²，ME，Pbias和CF）用于模型性能评估。上游水域藻华的变化不明显，因为与其他地方相比，藻类生长的营养水平不足。另一方面，随着中游区养分浓度的增加，藻华大量增加。堰建成后，上游和中游河道藻类生长增加。但是，富营养化下游区域的位置显示出相反的结果，表明在建造堰之后，藻类生长总体上减少了，但冬季除外，这表明水力滞留时间增加最多。由于堰的构造，这些结果似乎对藻华产生了正面和负面的影响。在富营养化地区，负面影响似乎更大，这是由于通过堰结构增加水深导致平均光效应降低，在营养水平上起着主导作用。洛东河堰的建设对藻类发生的影响如下：1）随着水力滞留时间的增加，营养充足的藻华增加。2）当养分充足时，平均光利用率成为藻类生长的主要因素；3）温度影响不是河流水动力变化的重要藻类生长限制因素。但是，这些结果在模型和数据准确性方面都有局限性。为了将它们用于水资源管理，