According to the principle of water balance, the groundwater balance equation in this area is established.
Mathematical expression:
Investigation and Evaluation of Groundwater Resources Potential and Eco-environmental Geology in Sanjiang Plain
Where: the recharge amount of Qi is the total recharge amount of groundwater in the I-th calculation unit, m3/a; Qi discharge is the total groundwater discharge of the I-th calculation unit, m3/a; The groundwater exploitable quantity of the ith calculation unit is the homogeneous mining, m3/a; Qi vertical recharge is the vertical recharge of groundwater in the I-th calculation unit, m3/a, including the recharge of precipitation infiltration and the recharge of canal irrigation field; Qihe River recharge, Qi marsh recharge and Qi adjacent area recharge are river recharge, vertical recharge and lateral runoff discharge to adjacent areas of groundwater in the I-th calculation unit, m3/a; Qi evaporation, Qi river discharge, Qi swamp discharge and Qi neighboring discharge are the I-th calculation unit, including groundwater evaporation, river discharge, swamp wetland discharge and runoff discharge to neighboring areas, m3/a; Change of groundwater reserves in the ith calculation unit, m3/a; N is the number of calculation units, taking 47.
Calculation method:
In order to ensure the sustainable utilization of groundwater resources, swamp wetlands will not be degraded by blind exploitation of groundwater, and groundwater in Sanjiang Plain will be exploited in a balanced way. Under the condition of multi-year balance, the change of groundwater reserves should be zero, that is, δ q reserves = 0, and the groundwater level is basically stable under the condition of multi-year balance. From the composition of groundwater resources and the model of regional groundwater flow system, it can be seen that the dynamic change of groundwater level is not only related to meteorological and hydrological conditions, but also related to groundwater exploitation. Therefore, if the multi-year equilibrium condition of δ q reserve = 0 is satisfied, the multi-year average exploitable groundwater resources in each equilibrium area must be reasonably determined. The calculation method is as follows:
Step 1: According to the precipitation and hydrological data of the work area for many years, determine the degree of abundance and drought in precipitation years in history, select the precipitation and hydrological data in wet years, normal years and dry years respectively, divide the periods by months, and calculate and determine the vertical recharge of groundwater in each period and unit respectively. Among them, all kinds of parameters used in the model are determined according to the identification results of the model, and it is assumed that the area of the existing canal irrigation area remains unchanged. Then, the vertical recharging intensity of each battery in each equilibrium area in each time period is obtained.
The second step is to calculate and determine the water level values of various boundaries according to each time period of wet year, normal year and dry year.
Thirdly, according to the principle of groundwater exploitation intensity distribution, an initial groundwater exploitable resource quantity (using the current exploitation quantity) is given and allocated to the monthly groundwater exploitation intensity.
Fourthly, the source-sink terms and boundary conditions determined above are substituted into the model to calculate the equilibrium of each equilibrium area in each period.
Repeat the above steps 3 and 4, and gradually adjust the exploitable groundwater resources until the change of total reserves in each balance area is zero in rainy year, normal year and dry year. At this time, the amount of groundwater exploitation resources obtained is the amount of groundwater exploitable resources under the condition of multi-year equilibrium, so as to determine the amount of groundwater resources under the condition of multi-year equilibrium in each administrative region.
Second, the calculation results
After repeated calculations, the equilibrium calculation results of each equilibrium area in the multi-year equilibrium period are shown in Table 4- 15. As can be seen from Figure 4-28, when the simulated exploitable resources are 37 1, 654, 38+0, 97.40× 654, 38+0.04 m3, the annual consumption and storage in dry years are 3607.44×654, 38+0.654, 38 respectively. See Figure 4-29 ~ Figure 4-34 for the characteristics of groundwater flow field in dry season (April) and wet season (September) of each calculation year.
Figure 4-28 Variation Diagram of Groundwater Reserves in the Whole Region in Different Periods of Multi-year Balance
Figure 4- 15 Table of Balance Calculation Results of Multi-year Balance Period
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Figure 4-29 Isogram of Groundwater in Sanjiang Plain in Dry Season in Wet Year
Figure 4-30 Isogram of Groundwater in Flood Season in Sanjiang Plain
Fig. 4-3 1 Groundwater Isogram of Sanjiang Plain in Dry Season in Normal Years
Figure 4-32 Isograms of Groundwater in Normal Year and High Year in Sanjiang Plain
Figure 4-33 Isogram of Groundwater in Dry Season of Sanjiang Plain in Dry Year
Figure 4-34 Isograms of Groundwater in Low Water Year and High Water Period in Sanjiang Plain
(a) groundwater recharge resources
The average annual groundwater recharge resources in the whole region (calculated by the average of abundant, average and dry years) is 5 14522.93× 104 m3, of which the vertical recharge is 338,654,38+042.65×104m3, and the net recharge of rivers is 583/kloc. The net recharge of the marsh wetland is 72,538.87×104m3, and the net recharge of the lateral runoff in the adjacent area is 45,526.86×104m3 (Table 4- 16). In vertical recharge, the rainfall infiltration recharge is 277 768.9 1× 104 m3, and the return infiltration recharge of canal irrigation field is 60 373.74× 104 m3, as shown in Table 4- 17 ~ Table 4-104m3 respectively.
Table 4-/KLOC-Calculation Results of Annual Average Groundwater Resources in 0/6 Years
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Table 4- 17 wet year (p = 75%) Statistical Table of Rainfall Infiltration and Replenishment in Administrative Region Unit: 104 m3
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Table 4- 18 Annual Average (p = 50%) Rainfall Infiltration and Replenishment Statistics of Administrative Region Unit: 104 m3
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Table 4- 19 Statistical Table of Rainfall Infiltration and Replenishment in Administrative Region in Dry Year (p = 25%) Unit: 104 m3
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(2) Groundwater discharge
Under the condition of multi-year balance, the groundwater discharge in the whole region: the net discharge of rivers is 22,402.12×104m3, the net discharge of swamps and wetlands is13,523.07×104m3, and the evaporation discharge of groundwater is 46,369.87×/.
(3) Groundwater exploitable resources
Under the condition of multi-year balance, the annual exploitable groundwater in the whole region is 37 1, 1 and 97.40× 1.04 m3 respectively. See Table 4-654, 38+06 for the exploitable groundwater resources in each administrative region.