The objective of this study is to evaluate the water quality of the Lien Son irrigation system in Vietnam and identify the critical pollutants that affect the system’s water quality. Firstly, the water quality at fifteen locations distributed along the main Lien Son drainage and irrigation canals was monitored in the dry season (from January to March) for 3 consecutive years (2018, 2019, and 2020) to collect nine physical, chemical, and microbiological parameters. And then, principal component analysis (PCA) and factor analysis (FA) were applied to extract and identify the critical pollutants which helps to preliminarily detect the potential pollution sources to the irrigation system. Results of PCA and FA showed the principal groups of pollutants which had a significant influence on the water quality of the system. Sampling locations LS7 and LS8 had the heaviest pollution. The primary factors that influenced the pollution of the system were organic matter (COD and BOD₅), nutrients (N-NH\(_{4}^{+}\) and P-PO\(_{4}^{3-}\)), sediment transport (turbidity and TSS), and coliform. These factors are usually associated with the sources of domestic wastewaters and agricultural runoff from the vicinity. This suggested that urgent actions should be taken to control domestic wastewaters and agricultural runoff from the vicinity so that they could not deteriorate the water quality of the system.

这项研究的目的是评估越南连日灌溉系统的水质，并确定影响该系统水质的关键污染物。首先，在干旱季节（从1月至3月）连续3年（2018年，2019年和2020年）对沿连山排水渠和灌溉主渠分布的15个地点的水质进行了监测，以收集9种物理，化学和微生物参数。然后，应用主成分分析（PCA）和因子分析（FA）来提取和识别关键污染物，这有助于初步发现灌溉系统的潜在污染源。PCA和FA的结果表明，主要污染物类别对系统的水质有重要影响。采样地点LS7和LS8的污染最为严重。影响系统污染的主要因素是有机物（COD和BOD₅），养分（N-NH \（_ {4} ^ {+} \）和P-PO \（_ {4} ^ {3-} \）），沉积物迁移（浊度和TSS）和大肠菌群。这些因素通常与附近的生活废水和农业径流有关。这表明应采取紧急措施控制附近的生活污水和农业径流，以免使系统的水质恶化。