Impact Of Land Use Change On Water Quantity And Quality Of Ganjiang River Basin

Studying the impact of land use changes in the Ganjiang River Basin on the water quantity and quality of the river can predict the future conditions of the water environment in the Ganjiang River Basin and provide data support for the environmental protection and management of the river basin.This paper takes the Ganjiang River Basin as the research area,interprets the land use data of the Ganjiang River Basin from 1986 to 2019 based on remote sensing images,analyzes the spatial distribution,area changes,dynamics,and transformation directions of land use changes,and uses the model to analyze The land use of the river basin in 2025 and 2030 will be predicted.The SWAT model was constructed based on the collected basic data of the Ganjiang River Basin,and the model was calibrated and verified.The results all met the accuracy requirements.Simulating the water quantity and quality of the river under different land use conditions in the Gan River Basin in 2025 and 2030,the main conclusions obtained are as follows:(1)According to Landsat remote sensing images from 1986 to 2019,the land use data of the Ganjiang River Basin in 8 phases are divided into six categories.Forest area has always accounted for the largest proportion,with an average proportion of 64.04%;the area of arable land is the second,with an average proportion of 26.28%;The total area of grassland,water area,construction land and other land is about 10%.(2)From 1986 to 2019,the spatial distribution of land use in the Ganjiang River Basin remained basically the same,but the land use area at various stages increased or decreased to varying degrees.During the period from 2015 to 2019,the construction land in the Ganjiang River Basin had the greatest degree of dynamics.31.66%,indicating the fastest growth rate of construction land during this period,an increase of 720.43km2;the area changes and dynamics of each land use category are not the same,and the conversion direction is not fixed.(3)The predicted land use in the next 2025 and 2030 of the Ganjiang River Basin is roughly the same as the existing spatial distribution,and woodland and cultivated land are still the most important categories.After comparing with 2019,it is found that construction land and grassland have been Increase,the arable land,woodland and other land has been decreasing.(4)Simulate the runoff,sediment,total nitrogen and total phosphorus of the Waizhou Station in the Ganjiang River Basin in 2025 and 2030,and use the simulation results of land use in 2019 as the base period to judge the results of other land use.The changes within the year,the land use years are analyzed in the order of 2025 and 2030,and the results show that the runoff,sediment volume,total nitrogen and total phosphorus under different land uses have changed.In the next 2025,under the RCP 2.6 and 4.5 emission scenarios,the average annual runoff,sediment volume,total nitrogen and total phosphorus will all increase.Under the RCP 8.5 emission scenario,the average annual runoff will decrease and total phosphorus will increase;Under the RCP 8.5 emission scenario,the annual average runoff,sediment,and total nitrogen will all increase.Under the RCP 4.5 emission scenario,the amount of sediment and total nitrogen will both increase;the next 2025 and 2030 annual average concentrations of total nitrogen and total phosphorus will be Within the standard range of Class III water.