Spatial Characterization of Seawater Intrusion in a Coastal Aquifer of Northeast Liaodong Bay, China

Abstract

The safety of groundwater resources in coastal areas is related to the sustainable development of the national economy and society. Seawater intrusion is a serious problem threatening the groundwater environment in coastal areas. Climate change, tidal effects and groundwater exploitation may destroy the balance between salt water and fresh water in coastal aquifers, leading to seawater intrusion. The threat of seawater intrusion has attracted close attention, especially in the coastal areas of northern China, and the accuracy and efficiency of seawater intrusion monitoring need to be improved. The aim of this study was to fill the blanks in seawater intrusion research in the coastal aquifer of the Daqing River Catchment, northeastern Liaodong Bay, China, and determine the extent and evolutionary characteristics of seawater intrusion in this area. In this study, historical chloride concentration data were used to trace the evolution of the salinization, and electrical resistivity tomography (ERT) was used to supplement the data in areas with limited hydrochemical data and to detect the saltwater/freshwater interface, especially in the area near the Xihai Sluice. The results show that seawater intrusion in the Daqing River Catchment is mainly caused by overexploitation of groundwater. Since 2012, strict controls have been placed on the groundwater exploitation rate, and the chloride concentration of 250 mg/L has receded year by year, with saltwater being significantly reduced by 2018. The Daqing River plays an important role in the saltwater distribution. The Xihai Sluice, located in the lower reaches of the Daqing River, intercepts and controls the seawater intrusion in a certain range by raising the level of fresh groundwater to intercept and control saltwater intrusion within a certain range. The research results also confirmed that a combination of geophysical and geochemical methods is of great value in studying seawater intrusion, especially in areas with limited available hydrochemical data. A monitoring network with ERT instruments and wells should be established to collect regular measurements of the electrical resistivity distribution, as well as the groundwater level and chemical composition.

Radium isotope assessment of submarine groundwater discharge and associated nutrient inputs in Eastern Liaodong Bay, China

“…As a result, the seawater intrusion area is mainly distributed in the sandy aquifer of the coastal zone. The phenomenon of seawater intrusion was investigated in the silt coastal zone, such as the Daqing River estuary (Ma et al, 2019;Zhu et al, 2020).…”

A Study on the Cause of Layered Seawater Intrusion in the Daqing River Estuary of Liaodong Bay, China

“…The coastline length of in the study area is about 6 km. The climate of the study area is continental monsoon type, with four distinct seasons and the same season of rain and heat [58]. The average annual precipitation was 600-800 mm from 1956 to 2016 [58,59].…”

“…The climate of the study area is continental monsoon type, with four distinct seasons and the same season of rain and heat [58]. The average annual precipitation was 600-800 mm from 1956 to 2016 [58,59]. The average annual evaporation was high, ranging from 1000 mm to 1200 mm because the average amount of annual sunshine hours can be between 2600 h and 2880 h. The maximum evaporation depth was 4 m. The average temperature ranged from 9 • C to 10 • C for many years, and the frost-free period is 180-210 days in every year.…”

Spatial Variability of Relative Sea-Level Rise in Tianjin, China: Insight From InSAR, GPS, and Tide-Gauge Observations

“…land and sea level are in a delicate balance. This makes the Tianjin coastal region more sensitive to environmental changes including, but not limited to, land subsidence, sea level rise [1], coastal erosion [2], saltwater intrusion [3], and salinification of soil and water [4], [5]. Among them, land subsidence had caused great adverse effects to the entire coastal region in Tianjin, with subsiding rates up to 110 mm/yr over the past 50 years [6].…”