Studies on the dynamic boundary of the fresh-salt water interaction zone of estuary wetland in the Yellow River Delta
Miao Yu, Yunzhao Li, Kun Zhang, Junbao Yu, Xuelian Guo, Bo Guan, Jisong Yang, Di Zhou, Xuehong Wang, Xue Li, Xin Zhang
Abstract
Under the interaction between freshwater and seawater, estuary wetland has obvious periodic flooding characteristics and salt gradient change, thus showing diversified ecological service functions. Based on the measured data of salinity in the field, monitoring data of river hydrology, tidal process and the elevation data of estuary geomorphology, the spatial pattern of salt distribution and the dynamic boundary and its area range of the fresh-salt water interaction zone (FSIZ) of the estuary wetland in the Yellow River Delta were studied. The results showed that the salinity of the estuary wetlands in the Yellow River Delta ranged from 0.40 g L−1 to 26.67 g L−1. The bandwidth variation range of the FSIZ in the river was 0.53–1.73 km, and boundary range in saltwater side of the FSIZ outside the river was 0.28–4.27 km. The area of saltwater zone in the Yellow River Delta estuary wetland accounted for >50% of the total area of the study area. The onshore area of estuary wetland was dominated by the FSIZ (38.06%–74.07%), while the area of tidal-freshwater zone only accounted for 3.87%–6.51% of the total onshore area. The dynamic boundary range of the FSIZ in the study area was approximately 140.80 km2 (about 36.01% of the onshore area), of which >92% was located on the saltwater side of the FSIZ. The boundary of saltwater zone, tidal-freshwater zone and FSIZ of the Yellow River Delta estuary wetland were scientifically divided and the dynamic boundary range of the FSIZ was clarified for the first time in the study. Our results can provide a scientific basis for well-understanding the ecological functions of estuary wetlands and the wetland classification restoration and management.