Inle Lake is the second largest inland lake in Myanmar. Floating gardens, mostly for tomato cultivation, are a unique and profitable method of agriculture used by people living on and around the lake. This study investigated the water quality of Inle Lake and how it has been affected by the different agricultural practices used in tomato cultivation on floating garden beds, by measuring pollution levels. Water samples were collected from the sites representing two types of agricultural practice from four villages. The first was designated as being grown under good agricultural practices (GAP), and the other as under non-good agricultural practices (non-GAP), with this study undertaken during wet season, 2019 and dry season, 2020. Two additional sets of water samples were collected as references. One of these sets was from the center of the lake and the other from an inlet stream to the lake. All water samples were analyzed for physical and chemical properties. The results found that Ca2+, Mg2+ and HCO3- were dominant in the lake surface water. The results showed significant differences in the mean values for some water quality parameters between the GAP and non-GAP of each study sites in both seasons. In particular, nutrient pollution from chemicals such as nitrogen and phosphorus from the non-GAP were significantly higher than those from GAP. Water quality index was calculated to describe the overall quality of lake surface water. It was observed that the water quality was almost threatened in the floating garden areas.  In comparison between two practices, the non-GAP gave the higher water quality index value than the GAP. This investigated that poor management of fertilizers usage has had a negative effect on the water quality of the lake. The differences seen in water quality from the GAP and non-GAP areas, point to ways to successfully manage sources of water pollution in order to better conserve the lake by sustainable agricultural production.

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