According to the above generalized hydrogeological conceptual model, the mathematical model of groundwater flow in the simulation area is described by the definite solution of differential equation (7.4):

Study on the protection and sustainable utilization of water resources under changing environmental conditions

Where: h is the groundwater level, m; K is the permeability coefficient, m/d; D is the elevation of aquifer bottom plate, m; E is the vertical recharge intensity of aquifer, m/d, which mainly includes atmospheric precipitation infiltration recharge and river leakage recharge; F is the exploitation intensity of aquifer, m3/(a km2), which mainly includes the exploitation amount of industrial, agricultural and domestic water in suburban counties; Qi—— groundwater exploitation amount of urban waterworks and self-provided wells, m3/d; H0 is the initial water level, m; ω is the calculated area; μ is the water supply of aquifer; Qi(x, y, t) is the single-width recharge of the secondary boundary, m2/d.

7.4.2.2 spatio-temporal dispersion

The year 2004 is selected as the horizontal year for model identification, and the data of this year are solid and continuous, which can well reflect the aquifer structure, hydrogeological parameters and aquifer boundary properties. The validity period of the model is determined from April 2004 to July 2007, * *1110d. The calculation area is divided into rectangular grids. Because the calculation area is a funnel area where the groundwater level drops, the hydraulic gradient of groundwater is steep and the grid area is small. * * * It is divided into 47×58 units with 2726 nodes, and the unit area is about 0.37km2 (Figure 7. 14). The model is solved by Visual Modflow software of Waterloo Hydrogeology Company in Canada.

Figure 7. 14 Calculation Area Division Diagram

Hydrogeological parameters of 7.4.2.3

According to the results of hydrogeological exploration in recent 50 years, referring to the single-hole pumping test data of wells on the west side of the village, the permeability coefficient (333.6m/d) and hydraulic conductivity coefficient (6672.0m2/d) obtained from the single-hole steady-flow pumping test, and the permeability coefficient (382.2m/d) and hydraulic conductivity coefficient (7644.2m2/d) obtained from the unsteady-flow pumping test of hole groups. The hydraulic conductivity is 7 158. 1m2/d). In addition, the initial values of hydrogeological parameters are set by collecting previous parameters (Table 7. 13).

Table 7. 13 Permeability coefficient obtained from unsteady flow pumping test of the first few hole groups

7.4.2.4 yuanhuixiang

The aquifer in the calculation area mainly receives atmospheric rainfall infiltration recharge, reservoir leakage, channel leakage and groundwater lateral recharge. Because the buried depth of groundwater level in the calculation area is more than 20m, evaporation can be ignored, and the main drainage method is manual drainage.

(1) Data of rainfall infiltration system determined by vertical recharge intensity of research results in Shijiazhuang in recent 50 years.

The vadose zone in Shijiazhuang urban area is thick, generally more than 40m, and gradually decreases to the periphery. According to the characteristics of lithologic structure, Hutuo River Valley is dominated by gravel, with thin loam and clayey silt interlayer. Zhengding County-Hanjialou area north of Hutuo River is the combination zone of Hutuo River and Seabuckthorn River alluvial fan, and the vadose zone is mainly composed of gravel layer and thin clayey soil. From the south of the Hutuo River second terrace to the urban area of Shijiazhuang, there is a lithologic combination of clayey soil and sandy soil, the surface layer is a loamy layer of 3 ~10m, and the lower part is an interbedded layer of medium fine sand, gravel, loamy and clayey silt. In Tatan area and Liucun-Fangcun area, west of Liu Ying-Dahe and south of Shijiazhuang, the lithology of vadose zone is mainly cohesive soil with a thin layer of medium-fine sand, in which the surface of piedmont zone is loam, and the loess gravel layer is generally below 3 ~ 5m. Considering various influencing factors of precipitation infiltration, combined with the results of neutron moisture meter in Research on Scientific Management of Groundwater Resources in Shijiazhuang City (1987), the infiltration coefficient (0.4 14 for the gravel layer in Dasun Village) is determined. According to the results of Special Report on Comprehensive Evaluation of Hydrogeology, Engineering Geology and Groundwater Resources Exploration in Huang-Huai-Hai Plain (Hebei Part) (1982), the precipitation infiltration coefficient is divided. The permeability coefficient of Hutuo river valley is 0.35 ~ 0.40; The first terrace on both sides of the valley is 0.30 ~ 0.35; Below the dam of Huangbizhuang Reservoir—the area south of the second terrace line from Jia Cun to Xisanzhuang to Hutuo River, the area from Datan to Song Cun to Zhongliangling in the south of the city, and the area from Taitou to Dasonglou in the southwest of the calculation area is 0.20 ~ 0.30; The permeability coefficient of Dahe and the piedmont zone west of Liu Ying-Gao Qian decreases from east to west, generally 0.10 ~ 0.20; The permeability coefficient of urban built-up area (urban area, Zhengding county and copper smelting) is less than 0. 10. Leakage recharge intensity of rivers and canals. The Hutuo River seepage recharge groundwater is to connect groundwater with surface water in the form of ultimate seepage intensity. On the basis of predecessors' work, according to the seepage test and observation data of sand pit seepage, the initial values of the limit seepage recharge intensity of each river reach are given. In the simulation process, it is adjusted according to the river flow data and groundwater dynamics. The leakage recharge of Jin Shi Canal, Yolanda Canal and San Ji Canal is mainly based on the previous work, and the leakage recharge coefficient is given accordingly. The leakage recharge coefficients of Jin Shi Canal, Yolanda Canal and San Ji Canal are 0.048, 0.22 and 0. 135 respectively. The regression coefficient of groundwater recharge by farmland irrigation water infiltration is 0. 165. The above values are converted into surface replenishment intensity according to different time periods. Input it into the model as the initial value, and finally determine its value after simulation and identification.

(2) The groundwater exploitation amount is determined according to the statistical data of actual exploitation amount of water resources management department (Table 7. 14).

Table 7. 14 Statistical Table of Annual Production

Initial water level in 7.4.2.5

The start time of model identification is July 2004. The initial water level of the aquifer (Figure 7. 1 1) is determined according to the regional water flow pattern and the observation data of groundwater level inside and outside the calculation area in July 2004. Model identification and verification The model identification stage was from July 2004 to July 2007, and it experienced dry season and wet season. The law of groundwater level rise can comprehensively reflect aquifer characteristics, hydrogeological parameters, boundary conditions and source-sink terms. After identification, the division of precipitation infiltration coefficient is shown in Figure 7. 15 and Table 7. 15. See Figure 7. 16 and Table 7. 16 for the zoning of aquifer permeability coefficient. See fig. 7. 17 for the fitting of flow field in July 2007, and fig. 7. 18 for the fitting of representative observation wells in the identification period.

Table 7. 15 Table of Precipitation Infiltration Coefficient

Fig. 7. 15 zoning map of precipitation infiltration coefficient

Table 7. 16 Hydrogeological Parameter Zoning Table

Fig. 7. 16 Hydrogeological Parameter Zoning Map

Figure 7.17 Fitting curve of water level in 2007

Fig. 7. 18 Fitting between the calculated value of observation well and the measured value.

From the above model identification and verification stage, the groundwater level fitting of representative observation wells (Figure 7. 18) shows that observation wells SH9 and SH 102 are close to the water source of Hutuo River, and they are continuously and stably mined every day, which is not affected by seasons, and the water level drops nearly linearly, which is in line with reality. The other four holes are in agricultural areas. Due to seasonal and intermittent mining, the water level drops in a curve, which is in line with reality. In addition, from the regional flow pattern (Figure 7. 19), the calculated flow field is basically consistent with the measured flow field, which shows that the established numerical model of groundwater flow can basically describe the movement characteristics of groundwater flow in the proposed groundwater reservoir area, and the hydrogeological parameters selected by the model are basically reasonable, so the model can be used for prediction.