Analysis of surface water changes and driving force in Yellow River Delta from 1986 to 2016

Surface water played an extremely important role in the formation of Yellow River Delta, ecosystem evolution and social and economic development. In this paper, the combination of threshold method and manual vectorization are used to obtain the distribution of surface water of Yellow River Delta in 1986, 2001 and 2016. The trajectory analysis method is used to construct the transformation trajectory of surface water and analyze the evolution trend of the trajectories. The driving factor index system for the evolution of surface water in Yellow River Delta is constructed, from three aspects of natural environment socio-economic and geographical location. According to the trajectory of surface water transformation, the multi-class logistic regression model was used to analyze the genesis and analyze the driving mechanism of surface water evolution within 30 years. The results show that: 1) From 1986 to 2016, the surface water area of the Yellow River Delta increased by 1 161.53 km2, except for river showing a decrease, which was transferred to 63.32 km2, and decreased by 33.49 km2. Reservoir, pond and salt and aquaculture pond all showed an increasing trend and increased by 84.88, 63.82 and 1 046.33 km2, respectively. Unused land to the salt pond culture pond is the largest type of change in the study area. Construction land and pond are the main source of reservoir increase, and the abandonment of small reservoirs is the main way to reservoir reduce. The mutual transformation between cultivated land and pond is the most important form of trajectory transformation in the study area. Unutilized land is the main source of expansion of the salt and aquaculture pond, and farm land is the main flow of its reduction. 2) Logistic regression analysis found that the driving forces of different types evolved differently. Geographical location is the main factor affecting reservoir evolution. Distance from coastline and Distance from township are the leading driving factors for transforming into reservoir. Distance from township is the leading driving force for transforming from reservoir. The evolution of salt pond culture ponds is influenced by socio-economic and location. Aquatic production, population density, distance from city center, distance from Yellow River and gross national product are the main drivers of the transforming into salt and aquaculture pond. Distance from city center has become the dominant factor in controlling the transforming from salt and aquaculture pond in the study area. The conversion of pit pond is affected by location and socio-economic. Distance from townships, population density, and distance from coastline are the main driving factors. In general, the surface water in Yellow River Delta showed an increasing trend from 1986 to 2016, and due to the different types and effects of surface water, the evolution characteristics and driving forces of surface water show significant differences. Natural factors have little impact on the surface water bodies of the Yellow River Delta. Location factors and socio-economic factors are the main influencing factors for surface water changes in Yellow River Delta.