Study on the Change of River Connectivity in Qingshui River Basin from 1980 to 2015

WANG Kun, XU Chao, WANG Wenjie, et al

1. School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083; 2. Key Laboratory of Soil and Water Conservation of State Forestry Administration, Beijing Forestry University, Beijing 100083; 3. Chinese Research Academy of Environmental Sciences, Beijing 100012; † Corresponding author, E-mail: wuxq@bjfu.edu.cn

Abstract In order to reveal the changing rules of regional water system connectivity under the development of urbanization, this paper takes Qingshui River, a tributary of the Yongding River, as an object, integrates remote sensing imagery, statistical data, and land use data, uses the comprehensive evaluation system for river connectivity, combining the longitudinal connectivity of rivers based on the cumulative effects of barriers and the lateral connectivity of rivers based on the effects of catchment fragmentation, and systematically studies the connectivity changes of water systems in the Qingshui River Basin from 1980 to 2015. The results of the study indicate that based on expert knowledge and combined with the actual situation of the Qingshui River, the barriers of the Qingshui River can be divided into four types: reservoirs, sluice gates, diffuse bridges, and river accumulations. During the study period, the number of barriers continues to increase. In 2000, the number of barriers increases by 10.4% in comparison with 1980 and increases by 23.9% in 2015. From 1980 to 2015, the longitudinal connectivity of the Qingshui River Basin as a whole shows an upward trend. The proportion of the watershed with poor vertical connectivity gradually decreases from 40% in 1980 to 14% in 2015. The areas with increased vertical connectivity are mainly concentrated in the eastern and central parts of the basin, and the connectivity in the southwestern part of the catchment area deteriorates. The overall change in river lateral connectivity is not significant, with the western part of the basin decreasing and the eastern part having improved.

From 1980 to 2015, the comprehensive connectivity of the Qingshui River Basin shows an overall upward trend. The proportion of catchments with poor comprehensive connectivity is from 26% in 1980, 17% in 2000 and 17% in 2015, respectively. The areas with increased connectivity are mainly concentrated in the east of the basin, while the connectivity in some areas in the southwest of the basin is always poor. The study reveals the law of connectivity changes in the basin during the urbanization process in Beijing, Tianjin and Hebei, and can provide a scientific reference for regional flood prevention and disaster reduction and river ecological rehabilitation. Key words barrier; integrated connectivity; land-use fragmentation; catchment; Qingshui River