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

Abstract

Groundwater over-pumping in estuary cities leads to a series of groundwater environmental problems that seriously restricts economic development. On the basis of field investigation and long-term monitoring data analysis, a three-dimensional numerical model was built in the estuary of the Daqing River in Liaodong Bay, China. The Quaternary overburden can be generalized into five layers according to particle composition and parameters in the vertical direction. There are many scattered irrigation wells pumping in the second layer, and three water source areas mainly pumping groundwater in the fourth layer. Long-term over-pumping in multi-layered aquifers causes onshore layered seawater intrusion. The laws of layered intrusion under the layered pumping were calculated and analyzed with SEAWAT-2000, and the sensitivity was analyzed with the Sobol method. Results showed that the intrusion area had an obvious layered law. Layered pumping directly affected the layered intrusion area, as different permeability, tide and barrage further affected it. The prediction study showed that the cone of depression recovered after the pumping-limit of water source areas, and the intrusion area started to retreat in the fourth layer. At that time, the pumping quantity of irrigation wells became the main reason for the increase of the intrusion area. If the water source areas are used to bear part of the irrigation demand, so as to reduce the pressure of pumping in the second layer, the overall intrusion area can be reduced by about 0.23 km2 under the same pumping quantity.

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

“…The landform of the eastern coast of Liaodong Bay area changes from the eastern part to the western part regularly, due to the effects of structure, lithology, and neotectonic movement TSGSBOLP (The Seventh Geological Survey Brigade of Liaoning Province), 1973. Generally speaking, the geomorphic types are low mountains, high and low hills, and alluvial plains from east to west (Zhu et al, 2020). The alluvial plain in the research area is bordered by the mountains in the eastern part and by the sea in the western part (Figure 1).…”

“…The highest temperature (37°C) occurs in July and the lowest temperature (−21°C) occurs in January. 1 The annual precipitation ranges from 600 to 800 mm, and the evaporation for each year is between 1,000 and 1,200 mm (Zhu et al, 2020). The main rainfall intensities occur from July to September, which is about 80% of the annual precipitation (Pei et al, 2019).…”

“…The form of groundwater discharge includes the discharge to the river, groundwater runoff, evaporation, and artificial exploitation. The groundwater flows from east to west, and its velocity changes with the aquifer thickness, permeability, and topography (Zhu et al, 2020). The velocity of groundwater flow decreases in the coastal zone as the hydraulic conductivity of the aquifer decreases.…”

“…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).…”

Assessment of Groundwater Resources in Coastal Areas of Pakistan for Sustainable Water Quality Management Using Joint Geophysical and Geochemical Approach: A Case Study

“…On the contrary, freshwater pressure on seawater decreases due to a relatively excessive extraction of freshwater, and as a result, seawater migrates farther inland [15][16][17]. Seawater intrusion reduces freshwater accessibility, and hence, degrades sustainable freshwater quality [18][19][20][21]. The intrusion of seawater into inland groundwater has become one of the most important ecological problems that influences sustainable groundwater resource management [22].…”