Study On Spatio-temporal Variation Characteristics Of Chla Concentration In Dianchi Lake Under The Background Of Urbanization

Ecological issues are one of the most important issues facing mankind in the 21st century,and they are also hot topics of research by experts and scholars from various countries and have received widespread attention.In recent years,with the rapid devel-opment of socio-economic ecological environment problems have become increasingly prominent,the protection and governance of the ecological environment is imminent.General Secretary Xi pointed out at the Party’s 18th National Congress:"Green moun-tains and green mountains are golden mountains and silver mountains."This is a new important content of the construction of ecological civilization and an important meas-ure to promote the ability of ecological environment governance.In the past 30 years,with the acceleration of the urbanization process and the impact of human activities,the eutrophication of Dianchi Lake has continued to intensify,seriously hindering the sustainable development of Kunming City.To investigate the temporal and spatial var-iation of Chla concentration has caused great attention and attention from Chinese gov-ernment departments and related scholars.Therefore,analyzing the temporal and spa-tial variation of chlorophyll a（Chlorophyll a,Chla）concentration in Dianchi Lake and exploring the influence of internal and external factors on Chla concentration is to con-trol and improve Dianchi Lake.The foundation of the aquatic environment is also the key to preventing and controlling water pollution in Dianchi Lake.This paper uses Dianchi Lake and its watershed as the research area,and collects10 water quality monitoring stations Historical data from 1998 to 2016,water quality data measured by the research team,and human factors（civilian car ownership,popu-lation of Dianchi Basin,Gross Domestic Product（GDP）,impervious surface（Impervi-ous surface,ISA））,the preliminary research conclusions are as follows:（1）The spatio-temporal variation process of water quality in Dianchi Lake and its driving factors from 1998 to 2016 were analyzed,and the quantitative relationship be-tween Chla and related water quality factors in Dianchi Lake was discussed.（2）（2）The K-T variation was used to extract the humidity component from the TM image,and the wetland area of the Dianchi Lake Basin was calculated.Correlation analysis showed that the correlation between Chla concentration and the area of vegetation wetland in Dianchi Lake Basin（R=0.884）was significant at 0.05.（3）The regression analysis method is used to construct the inversion model of Chla concentration in Dianchi Lake.The correlation analysis shows that the Chla concentration has the highest correlation with the band combination R655/R（483-561）,and the Pearson correlation coefficient is0.867.The fitting effect of the univariate quadratic equation model is the best,R² is0.8565,and the average relative error is 13.2%.（4）The impermeable surface of Dianchi Lake watershed is extracted by INDBI method,and the temporal and spatial variation characteristics of impervious surface of Dianchi basin are analyzed.（5）The results in-dicated that Chla concentration was significantly and positively correlated with the chemical oxygen demand(COD_Cr),the Dianchi Lake watershed gross domestic prod-uct（GDP）,and the impervious surface area（ISA）of the watershed,in addition to the total phosphorus（TP）,biochemical oxygen demand（BOD₅）,ammonia hydrogen（NH₃-N）,water temperature（WT）,and civil vehicle ownership.Moreover,a significant and negative correlation was noticed between Dianchi Lake watershed GDP and NH₃-N,BOD₅,TP,total nitrogen（TN）,and comprehensive nutrition state index（TLI）.The Di-anchi Lake population was negatively correlated with TP,TLI,and BOD₅.（6）The re-sults show that the Chla concentration of Dianchi Lake tends to spread from north to south and then to southwest,and the Chla concentration increases significantly in Xishan District and Chenggong District with rapid urban development.The concentra-tion of Chla in Dianchi Lake was affected by both internal factors,and external factors such as anthropogenic activities,the latter of which was the main cause of the contin-uous deterioration of the lake water quality.