Research On The Response Of Water And Sediment Processes To Landscape Pattern Changes In The Liaohe Main River Basin

In recent years,the water and sediment situation in China has changed significantly.The runoff and sediment transport of major rivers have shown a downward trend,resulting in a series of problems such as the retreat of estuary deltas and the intensification of water resources conflicts.The Liaohe River is one of the seven major rivers in my country and is known as the mother river of the Liaoning people.In this study,the main stream of the Liaohe River was taken as the research object,and various statistical methods such as Mann-Kendall trend and mutation test were used to systematically analyze the temporal and spatial variation characteristics of water and sediment in the basin;The model builds the relationship between landscape pattern and watershed runoff and sediment transport process,and explores the response relationship of water and sediment process to changes in landscape pattern.The main findings are as follows:(1)From 1987 to 2018,the annual precipitation in the Liaohe River Basin showed an insignificant downward trend,and there was no obvious mutation during the study period.The runoff and sediment transport in the main Liaohe River Basin generally showed a decreasing trend,and the runoff all changed abruptly in 1995.The Tongjiangkou-Tieling interval is the main water-producing area of the main stream of the Liaohe River,and the main sand-producing area tends to shift to the Mahushan-Ping’anbao interval,but the Tongjiangkou-Tieling interval is still the main source of sediment in the lower reaches of the Liaohe River.The main driving force for the reduction of runoff and sediment transport in the main stream of the Liaohe River.(2)Under the influence of human activities,construction land continued to expand from1987 to 2018,and the areas of grassland,wetland and forest land decreased to varying degrees.This situation improved after 2010.The separation and fragmentation of the watershed landscape increased,and the connectivity decreased.Cultivated land is the dominant landscape type in the main stream of the Liaohe River.During the study period,the patch shapes of grassland and woodland tended to be regular and simple,while the disorderly expansion of construction land resulted in an increase in the degree of fragmentation of cultivated land and grassland and a decrease in the degree of aggregation;the increase in the degree of fragmentation of water bodies,the degree of spread is weakened,the degree of aggregation is reduced;the degree of forestland aggregation is reduced.(3)The area and spatial structure of the landscape are the main factors affecting the watersediment process in the watershed,among which the dispersal and juxtaposition index,fragmentation degree,maximum patch index and patch density are the key influencing factors of the runoff process;fragmentation degree,maximum patch Index and edge density are the key influencing factors of sediment transport process.After testing,the constructed PLSR model can effectively describe the relationship between landscape pattern and water-sediment in the watershed,and the PLSR model of sediment transport and landscape index is more accurate.To sum up,this study has identified the response relationship of watershed runoff and sediment transport to landscape pattern changes,identified key influencing factors,and provided a theoretical basis for the subsequent development of water and soil conservation in the watershed and the protection and utilization of water and soil resources.