## 1 Introduction  
In recent years, a large number of hydraulic tunnels have been built in China. While these hydraulic tunnels help to promote social progress, they also destroy the groundwater environment. When hydraulic tunnels are being excavated, a large volume of groundwater is lost, and the groundwater levels continuously decline, causing problems such as exhaustion of surface wells and springs, groundwater leakages, and ground collapse. Groundwater leakage reduces the soil water content, with serious consequences for the ecological environment, such as decreases in, or even the disappearance of, regional vegetation [1]. It is, therefore, very important to study how seepage fields of hydraulic tunnels evolve during construction and how groundwater levels change because of seepage around the tunnel. Numerous researchers have studied how tunnel construction affects the groundwater environment [2; 3; 4; 5; 6; 7; 8; 9; 10]. Underground engineering and construction disturb the groundwater environment and lead to decreases in the water resources across wide geographical areas and over considerable time periods; in some cases, the effects are irreversible and the groundwater does not recover [11; 12; 13; 14; 15]. When precipitation events occur during the construction of a tunnel, large amounts of groundwater are discharged from natural aquifers within a certain spatial range leading to reductions in the underground water levels and local changes in the groundwater storage characteristics, such as the evolution of landing funnels and changes in groundwater seepage fields. Given that these changes might compromise groundwater supplies, algorithms of underground water inrush into such tunnels have therefore been proposed to predict how the groundwater environment would be affected by the construction of a tunnel [16; 17]. Researchers have studied how the groundwater flow changes when rock tunnels are excavated and have found that groundwater circulation systems may be damaged by tunnel water gushing during excavation [18; 19; 20; 21; 22]. The surface water source and some spring points may dry up during water flushing accidents in the construction phase. Studies to date, therefore, have shown that underground engineering construction can have serious effects on the groundwater environment and the supply of groundwater resources [10; 23; 24]. During the construction of an ultra-long subway tunnel in Seoul, South Korea, in 2008, the groundwater level dropped dramatically in some parts of the project area, and a large number of underground wells dried up and were abandoned. Calculations showed that the average annual water yield reached \(6.3\times 10^{7}\) m\({}^{3}\), and the local groundwater environment was severely damaged [25]. During the construction of a 7300 run tunnel on the high-speed railway line between Malaga and Cordoba in a karst area of southern Spain, there was a large water inrush with an instantaneous flow of up to 800 L/s, which resulted in serious shortages of groundwater supplies for drinking and irrigation in that area [26]. In 2009, because of a drainage problem in the Frizenzuola Tunnel, Italy, five streams in the tunnel site were cut off and 12 springs dried up [27]. Japanese scholars studied the groundwater levels during the construction of a tunnel in Matsumoto City, Japan. They found that a large amount of groundwater gushed into the tunnel, leading to groundwater leakages, exhaustion of springs within the scope of its influence, and decreases in the river flow in the discharge area [28]. In 2010, the Yujiawan Reservoir dried up during the construction of the Xiyong Tunnel in Chongqing, thereby damaging the function and production ability of approximately 50 mu of farmland in Jingang Village. In March 2012, drinking water sources were depleted in Shiyuan Village, Zhongliang Town, during the construction of the Zhongliangshan Tunnel on the Lanzhou-Chongqing Railway, and more than 1300 people and 10 businesses experienced severe water shortages.