An Approach To The Determination Of Hydraulic Conductivity And Optimal Schemes Of Groundwater Withdrawal For The Ninghebei Wellfield In Tianjin

With the reforming and economic development, the quantity of water demandedby Tianjin city increase with time. As a source of water supply in the developingregion of economics and technology of Tianjin, the Ninghebei wellfield is one of theimportant projects of Tianjin. The construction of large water resources of city notonly needs provement of insurance of water quantity and quality but also exploit thegroundwater economically.Ninghebei wellfield is located in the north of the Ninghe county, Tianjin city andthe south of Fengrun county, Hebei province. It is located in the Chezhoushansyncline, south of Yanshan Mountain. Groundwater aquifer is composed ofOrdovician limestone. It covers area of 547.32 km2, and its effective thickness isabout 400 m. It extends as north-east syncline and it is deep in south-west andbecomes shallow in north-east. In the Chezhoushan it outcrops. The limestone aquifercontains large quantity of water and the single well's yielding amounts 1500-10000m3/d.Hydraulic conductivity K is one of the important hydrogeologic parameters. Inthis paper, through analyzing the data of the pumping test of single well conducted inthe Ninghebei groundwater wellfield, the test can be viewed as the pumping test ofsingle well fully penetrating the confined aquifer with steady flow and constantpumping rate.Based on the analysis of the test, two traditional methods, such as the Dupuit'smethod and straight-line distance-drawdown method, are employed to calculate thehydrogeologic parameters. The results of the calculation are compared with thosepresented by former scholars. On the basis of the results of calculation andcomparison in this paper, the result of the hydraulic conductivity K is 20 m/d. Theresult is thought to be accordant with the lithology of the test region. The interactioneffect with the results of hydraulic conductivity is also calculated.Finally, a groundwater resource management model has been established withpumping water quantity as decision-making variable and drawdown as inhibitingcondition, then calculating the model with simplex method. If the water quantitysupplied for limestone aquifer through leakage section reach 100 thousand m3/d,considering the wells situation and the need for water quantity, there are two schemesadvanced. One model is established with 15 wells' pumping water quantity asdecision-making variable. Calculating the model, the results is exploiting 11 wells atthe same time which are 1,3,4,5,6,7,8,10,11,14,15and so on and the pumpingwater quantity is separately 8317.39,7728.83,2893.22,13971.93,13683.91,3030.55,3020.67,15652.94,4433.44,21815.74,and 5451.79 m3/d. Another modelis established with 9 wells' pumping water quantity as decision-making variable.Calculating the model, the results is exploiting 8 wells at the same time which are 1,3,5,6,9,10,14,15and so on and the pumping water quantity is separately 9543.98,8271.25,15680.08,14263.72,7614.34,16591.02 ,22080.07,and 5955.55 m3/d.