**5. Conclusions**

Images from the GF-1 satellite helped to establish retrieval models for concentrations of Chl-a and TSM in Poyang Lake in different seasons. The retrieval model that obtained the best fit for each season, respectively, was used to analyze the spatial and temporal variations of the concentrations of Chl-a and TSM for that season.

For Chl-a, the results showed that the wavelengths corresponding to bands 1, 3, and 4 of the GF-1 images were the most sensitive to changes in the concentration of Chl-a. Moreover, the APPEL model was used to establish the band combination, thus obtaining the retrieval models of Chl-a concentration for different seasons. The highest concentrations of Chl-a in Poyang Lake were mainly observed near the channel that connects the north of the lake to the Yangtze River, the places where the Ganjiang, Fuhe, Xinjiang, Raohe, and Xiushui rivers enter the lake, and near to the lake shore. In the central area of the lake, the concentration of Chl-a was relatively low and uniform. Regarding the temporal variation of Chl-a in Poyang Lake, the concentration was the highest in summer (August 2015), second-highest in autumn (October 2015), and lowest in winter (January 2016).

For TSM, the results showed that the correlation between the reflectance and TSM concentration was the highest for wavelengths corresponding to band 3 of the GF-1 satellite images. The highest TSM concentrations in Poyang Lake were mainly observed in the channel that connects the north of the lake to the Yangtze River, and in the lake's main central channel. The TSM concentration in Junshan Lake was relatively low and it changed little between seasons. The TSM concentrations near the inlets of the Ganjiang, Fuhe, Xinjiang, Raohe, and Xiushui rivers to Poyang Lake were lower than that in the channel that connects the north of the lake to the Yangtze River. Regarding the temporal variation of TSM concentration in Poyang Lake, the concentration was highest in autumn (October 2015), second highest in winter (January 2016), and lowest in summer (August 2015).

**Author Contributions:** Conceptualization, J.X. and Y.W.; Methodology, J.X.; Software, C.G.; Investigation, J.X. and C.G.; Data curation, J.X. and C.G.; Writing—original draft preparation, J.X. and C.G.; Writing—review and editing, J.X. and Y.W.; Supervision, Y.W.; Funding acquisition, J.X. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was funded by the National Natural Science Foundation of China (grant no. 41471298), the Key Research and Development Project of Jiangxi Province (grant no. 20192ACB70014), the Opening Fund of Key Laboratory of Poyang Lake Wetland and Watershed Research (Jiangxi Normal University), Ministry of Education (grant no. PK2018002), the Science and Technology Project of Education Department of Jiangxi Province, and the Young Talents Project of Jiangxi Normal University.

**Acknowledgments:** We appreciate the insightful and constructive comments and suggestions from the anonymous reviewers and the Editor that helped improve the quality of the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
