Groundwater resources in Guangdong-Hong Kong-Macao Greater Bay Area and its development potential

Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is one of the areas with the highest degree of openness and the strongest economic vitality in China. It has an important strategic position in the overall situation of national development. The future development of the bay area is inseparable from the support of water resources and a good water ecological environment. In recent years, with the rapid economic development of GBA, the population is increasing rapidly, the water demand is increasing. As a result, the water environment is deteriorating obviously, and many cities have a single water source, the local water resources storage capacity is limited, and the degree of water security is insufficient. Groundwater is an important part of water resources, with the characteristics of stable water quantity and good water quality, which can be used as an important emergency standby water source. Starting from the groundwater resources, based on the systematic summary of groundwater resources status, characteristics, development and utilization potential, some suggestions in water source of GBA were put forward. It is concluded that groundwater can be divided into three categories: pore water of loose rock, karst water of carbonate rock and fissure water of bedrock, among which pore water of loose rock and fissure water of bedrock are the most widely distributed. The hydro chemical types of groundwater in the bay area are relatively complex, with HCO₃-Na、HCO₃-Ca and HCO₃-Na+Ca as the main types in the hilly area, HCO₃+Cl-Na and HCO₃ +Cl-Na+Ca as the main types in the alluvial plain and intermountain basin, and Cl-Na brackish water as the main type in the delta area. The main streams of Xijiang, Beijiang and Dongjiang constitute the main drainage channels of groundwater in the bay area. The tributaries are the local discharge datum of groundwater. The groundwater changes dynamically with the seasons. The overall quality of groundwater is good, class Ⅰ-Ⅲ water of which accounts for 66.25%. From hilly areas to delta plain, the water quality shows a trend of deterioration, especially in Guangzhou, Jiangmen, Zhongshan, Dongguan and other cities. The main factors exceeding the standard are ammonia nitrogen, chloride, fluoride, sulfate, etc. The degree of groundwater development and utilization is very low. Groundwater has basically not been developed and utilized in Dongguan and Zhongshan. Of all kinds of groundwater, carbonate karst fissure water has the potential of large-scale exploitation and utilization. Based on the comprehensive analysis of relevant data, 10 water-rich blocks such as Guanghua basin are proposed as emergency water sources, which can provide 418 million m³ of emergency water supply guarantee for GBA every year. In order to deal with the sudden water pollution and extreme arid climate and other large-scale water supply crisis, ensure the water safety of GBA, and promote the high-quality development of GBA, it is suggested to strengthen the basic hydrogeological survey of GBA, master the dynamic change of groundwater level, water quality and water quantity, and accurately calculate the groundwater storage that can be used for emergency exploitation.