Analysis Of Land Use Change Trend And Its Impact On Water Quality In Main Basins,Guizhou Province,Southwest China

Non-point source pollution from different land use is an important factor that impacts water quality;in recent years,the land use pattern has changed dramatically,thus affecting the quarter quality of rivers.Therefore,this study aims to explore the relationship between land use/cover change and its impact on water quality in Guizhou province.The nine main river basins in Guizhou province were chosen as research objectives.The data such as land use and water quality data for 2000,2010,and 2020 were used to investigate the relationship between land use change and surface water quality index based on the watershed scale.In order to get complete results,this study adopted environmental geographic information system（GIS）and remotely sensed techniques,Kuznets curve（EKC）,and statistical analysis such as Pearson correlations,cluster analysis,and multiple linear regressions analysis.The results revealed that the land use structure in the study area had changed intensely between2000 and 2020;Grassland,cultivated land,and forest decreased meaningfully;meanwhile,the artificial surfaces and water increased rapidly,and such changes may have led to countless contaminant loads.Furthermore,the grassland declines were significant in the Chishui-Qijiang basins with a total proportion of（-2.71%）and Yuanshui（-1.52%）and increased significantly in the Niulan river basin area with a total proportion of 1.19%.The areal proportion of cultivated land declined considerably in the Hengjiang basin（1.20%）;however,it increased vastly in the Duliu river basin（5.45%）.The leading decline in forest proportion was observed in the Duliu river basin（-1.28%）,while the highest increase was in the Chishui and Hengjiang river basins with the highest rate change in the forest land of 1.73%).The water bodies had the highest rate change proportion in the Beipan river basin（25.01%）.The artificial surfaces as the leading proportion rate change of all the classes in the study area over time;the highest increase was in the Duliu river basin（60.66%）and Niulan River Basin（58.21%）.A decrease in the proportion area of?? the artificial surfaces was only observed in the Nanpan river basin（8.78%）.The water quality features in the nine basins across Guizhou Province have a strong geographical distribution.For instance,the Hengjiang river,Duliu river,and Chishui-Qijiang river basins received the least pollution water.Therefore,the water quality of these basins was classified as II.However,the Beipan river,Wujiang river,and Yuanshui river basins were highly polluted,with water quality classified varying from II to IV.The water quality is related to pollution from point sources and non-point pollutants,such as agricultural flows,household waste,and industrial emissions.An average class of II was the pollution level found for all nine basins.Additionally,a countless portion of the water quality variables has improved from 2000 to 2020.The regression model revealed that the percentage of grassland area was a predictor for NH₃-N,and TN,indicating that the more grassland area is,the less NH₃-N and TN.In comparison,the forest was also a predictor for TN;however,the correlation coefficient was positive.Other use land types were eliminated from the model due to their insignificance.Furthermore,based on the Markov chain model,we simulated the land use and land cover change for future fifteen years.The result showed that artificial surface areas would gradually increase.However,keeping the current pollution management policy and economic growth,these changes might not cause negative impacts on water quality variables.The results provide effective techniques to evaluate river water quality,control water pollution,and manage land use by land use pattern.