Spatiotemporal Characteristics of Dissolved Oxygen in Typical Water Bodies of South China Based on Landsat Imagery (2013-2024)

The South China region is characterized by a monsoon climate with concurrent rainfall and high temperatures, featuring abundant precipitation, dense water networks, and numerous lakes. With the development of agriculture and industry, water pollution has become increasingly severe. Dissolved oxygen (DO), as a crucial indicator for water quality assessment, effectively reflects changes in water quality. In recent years, water quality in aquaculture ponds, rivers, and lakes has gradually improved due to advances in sewage treatment technology and strengthened water quality management. Based on Landsat 8/9 OLI satellite imagery, this study applied Rayleigh reflection atmospheric correction, combined with EMD decomposition and water body indices, to construct a random forest retrieval model for dissolved oxygen (R²=0.90). The study analyzed the spatiotemporal variations of DO concentrations in three typical water bodies across South China from 2013 to 2024. Results showed that: (1) DO concentrations in all three water body types exhibited an increasing trend from 2013 to 2024, with increases of 0.2%, 0.8%, and 2.4% in rivers, aquaculture ponds, and lakes, respectively; (2) In terms of average DO concentration, lakes maintained the highest levels (7.93 mg/L), followed by rivers (7.75 mg/L), while aquaculture ponds showed the lowest levels (7.41 mg/L); (3) Spatially, DO concentrations in rivers decreased gradually from upstream to estuaries, lake centers showed higher concentrations than shoreline areas, and aquaculture ponds demonstrated higher levels in mountainous and upstream river regions compared to lower-latitude coastal areas; (4) Seasonal patterns revealed that DO concentrations in rivers and lakes reached their minimum in summer and maximum in winter, while aquaculture ponds showed an opposite trend.