Study On The Relationship Between Land Use And Water Quality In Jilin Section Of Songhua River Basin

Land use change is closely related to the water environment and is an important factor affecting the change of water environment.Changes in land use patterns can change the water cycle through the flow of matter and the circulation of energy.Therefore,the water environment effect of land use change is currently an important research direction.Its research not only has important theoretical and practical significance,but also has important significance for the sustainable use of water and soil resources,sustainable development of society and the protection of ecological environment.This paper constructs a statistical relationship model between land use patterns and water quality indicators with different buffer distances centered on the river basin based on the analysis of land use change characteristics and water quality in the Jilin City section of the Songhua River Basin in 2013 and 2017,using hydrological analysis,spatial overlay analysis,Spearman correlation analysis,RDA analysis,scale effect analysis with Landsat TM/OLI satellite remote sensing image,DEM,water quality monitoring data,statistical data and images as data sources processed in the software of ENVI 5.1,ArcGIS 10.2,SPSS 19.0 and CANOCO4.5 and its scale effect is discussed.The results show that:(1)The main land use types in the Jilin City section of the Songhua River Basin are forest land and cultivated land,accounting for more than 90%of the total area of the river basin,and the proportion of construction land,water area,grassland and unused land is small.During the period of 2013-2017,the land use types in the study area changed in varyingdegrees,and the area of construction land showed an increasing trend,with the largest change range,and increased by 160.956 km~2 in five years,with an average annual increase of 40.239km~2;followed by cultivated land,which decreased by 142.439 km~2,with an average annual decrease of 35.610 km~2;forest land area decreased by 19.472 km~2;and the area of other land use types did not change much.From the perspective of change speed,land use type with the fastest area increase is construction land,which reaches 3.57%per year;while the land use type with the fastest area decrease speed is unused land,which is 0.21%per year,followed by cultivated land,which is 0.18%per year.During the period of 2013-2017,the transformation from cultivated land to construction land was the most important feature of land use change in this stage.(2)From 2013 to 2017,the water quality of the main stream and tributaries of theSonghua River in Jilin City was in good condition,and all the pollution indexes met the Class III standard of Surface Water Environmental Quality Standard.From the time point of view,the pollution degree of water quality of each section has increased in the past five years;from the space point of view,the pollution degree from upstream to downstream is aggravating,the pollution of downstream wall joints and whistle sections is serious,while the water quality of Baiqi section has improved.(3)The correlation between forest land,cultivated land,construction land and water quality indicators is significant,forest land and water quality pollution indicators arenegatively correlated,and cultivated land and construction land are positively correlated with water quality pollution indicators.Among them,the positive correlation between cultivated land and water quality is the most significant,followed by construction land,indicating that cultivated land and construction land have a significant effect on the deterioration of riverwater quality.Forest land can purify water quality,conserve water sources and conserve water and soil on a larger spatial scale,while grassland in the 100 m coastal zone shows a certainrole in retaining pollutants,grassland outside the 100 m zone has no obvious impact on river water quality.In terms of scale effect,the closer to the riverbank,the greater the impact of land use pattern on water quality,and the most significant impact is within 400 m,whichmeans this arear is the key area affecting water quality in Jilin section of Songhua River Basin.This indicates that land use structure in Jilin section of Songhua River Basin is an important factor affecting water environment quality of the basin.