Lake Diatas is a tropical lake surrounded by agricultural land prone to pollution. A multivariate approach to lake water quality will be useful for lake management. The study's objectives are to describe fertiliser use by farmers around the lake, the lake's quality and trophic state spatially, and to use a multivariate approach to lake water quality. The results of a survey showed that most farmers use synthetic fertilisers because of low fertility soil, with self-estimated doses applied. The levels of total nitrogen (TN), total phosphorus (TP), and Secchi depth (SD) marginally exceeded the regulatory standard. However, the trophic status of the lake indicates an intermediate level of nutrients. Principal component analysis (PCA) showed the presence of two main factors with a variance of 85.46% – which showed the important drivers for lake water quality is mainly affected by agricultural activities around the lake. Cluster analysis showed three groups with the same water quality characteristics: the first group consists of locations with higher sulphate levels, the second with low SD, and the third with higher levels of TN and TP. Clearly, agricultural activities affect lake water quality and management regarding land use around the lake is important to prevent pollution. HIGHLIGHTS Lake Diatas is a tropical lake surrounded by agricultural land prone to pollution.; The levels of TN, TP, and Secchi depth marginally exceeded the regulatory standard.; The lake indicates mesotrophic status.; PCA showed the important drivers for lake water quality are mainly affected by agricultural activities around the lake.;
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