Due to rapid urbanization, population growth, industrialization, and agricultural activities, there is an increasing demand for freshwater resources, leading to heightened pressure on watershed ecosystems. This study focused on the Nishan Reservoir, Qufu Sihe River, and Qufu Yihe River, conducting field investigations on these water bodies during the spring of 2021 and 2022. Water samples were collected and analyzed for key water quality indicators, including chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (AN), chlorophyll A, and algal cell density. This study unveiled notable correlations among various water quality parameters, including positive associations between BOD and COD, chlorophyll A and algal cell density, and inverse relationships with total phosphorus. Moreover, significant positive correlations were identified between total nitrogen and ammonia nitrogen, as well as between ammonia nitrogen and chlorophyll A. The study highlighted that the TP concentration surpassed the threshold of 0.20 mg/L in 2021, potentially exacerbating the proliferation of algae, leading to algal blooms and adversely affecting the aquatic ecosystem. This study emphasizes the significance of broadening the geographical scope and utilizing long-term datasets to discern trends, determinants, and management approaches pertinent to water quality. Furthermore, this study underscores the imperative of investigating the influence of nitrogen-to-phosphorus nutrient ratios on the composition and proliferation of algal populations, while also taking into account the potential impact of additional factors like light availability, temperature, and water flow on the dynamics of algal communities.

Tian, G.Z.; Xu, Y.M.; Gao, Y., and Wang, Y., 2020. Ecological environment of Erhai and Lashihai watersheds of the ancient tea horse road on the Yunnan-Tibet line. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 401-404. Coconut Creek (Florida), ISSN 0749-0208.To evaluate the soil and water quality, and to understand the historical background and modern civilization of Erhai and Lashihai watersheds of the ancient Tea Horse Road on Yunnan-Tibet line. Questionnaire survey was conducted at Erhai and Lashihai watersheds of ancient Tea Horse Road on Yunnan-Tibet line to collect water and soil samples. The chemical oxygen demand, total nitrogen, ammonia nitrogen and nitrate nitrogen were all higher in Lashihai water than in Erhai, with only total phosphorus in water body higher in Erhai. The soil pH and available potassium content were higher in Jade Dragon Snow Mountain than in Dali Cangshan Mountain, while the content of soil organic matter, alkaline nitrogen and available phosphorus was higher in Dali Cangshan Mountain than in Jade Dragon Snow Mountain. Soil Cr, Cd, Pb and As contents were higher in Jade Dragon Snow Mountain than in Dali Cangshan Mountain. Both Jade Dragon Snow Mountain and Cangshan Mountain have high soil nutrient levels, with the risk of exceeding criterion higher in soil heavy metals of Jade Dragon Snow Mountain than that of Cangshan Mountain. Nutrition of both Lashihai and Erhai waters is at a medium level, but Lashihai water is more organically polluted than Erhai.

(1) Although lotus ponds exhibit ecological benefits in wetland restoration, their efficacy in water purification and eutrophication mitigation remains unclear. (2) This study utilized Jinluo lotus pond as the experimental group and the adjacent river as the control. Five sampling points were established in each area, with water samples collected in June 2022, April 2025, and May 2025. (3) The pH, BOD, COD, TN, and NH₃-N concentrations in Jinluo lotus pond water are higher than those in rivers, while the TP, NO₃-N, Chl-a, and algal cell density in rivers are higher. However, there was no significant difference in the nine parameters (p > 0.05) in June 2022. The pH, DO, algal cell density, and algal biomass of the Jinluo lotus pond were significantly higher (p < 0.05 for DO); the concentrations of BOD, COD, TN, TP, NH₃-N, NO₃-N, PI, and Chl-a in rivers are higher, with significant differences in Chl-a (p < 0.05) in April 2025. The BOD, COD, TP, NO₃-N, and PI of the Jinluo lotus pond were relatively high (p < 0.05 for PI); the pH, TN, NH₃-N, DO, Chl-a, algal cell density, and algal biomass of rivers are higher, with significant differences in Chl-a (p < 0.05) in May 2025. The results showed that there was no significant difference in the four diversity indicators in June 2022, April 2025, and May 2025. There was no significant difference in the algal diversity indices, including species richness (S), Shannon–Wiener diversity index (H), Simpson diversity index (P), and Pielou evenness index (E) between Jinluo lotus pond and rivers. (4) Conclusions and Recommendations: The Jinluo lotus pond and adjacent rivers suffer from severe nutrient overload, especially with BOD, COD, and TN all being classified as Class 5 water. Expanding natural and constructed reed communities is recommended to enhance nutrient removal. However, given the limited purification capacity of lotus ponds, maintaining or increasing their area may not be justified.