Relation of bedrock aquifer property and geological structure in Mockcheon area, Korea
Abstract
In Korea, 72 companies are producing natural mineral water mostly from bedrock aquifer of different depths (Sung et al., 2002). It is important to insure quantity of natural mineral water. However, when several natural mineral-water companies are gathered in small area, the amount of producing water can be often limited by pumping rate of the companies in the area. In the study area, five natural mineral water producing companies (Siwon Semmul, Daejeong Eumryo, Jain Guanguang, Cheongsu Eumryo and Hanju Sikpum) are located in range of 2 km radius. Consequently, wells for natural mineral water of five companies and other private wells are drilled in Mockchun area. These wells produce groundwater from bedrock with total discharge rate 1,991m3/day. Thus, it is necessary to understand the hydrogeological characteristics of bedrock groundwater to preserve groundwater quantity in the study area. Geology was investigated to understand geological structure controlling aquifer characteristics in the study area. Precambrian metamorphic rocks (metamorphosed limestone, biotite schist, augen gneiss and porphyroblastic gneiss) are intruded by Jurassic porphyritic granite and two-mica granite and by numerous acidic and intermediate dykes. Alluvium overlies older rocks by unconformity (Kang and Lim, 1974; Shin et al., 1975). Two NS-direction thrusts are developed in the study area. Main aquifer is formed between the lower thrust and the upper thrust, and the lower thrust plays role as impermeable layer. It is considered that the main aquifer was developed by brecciation during the thrust faulting. Thus, pumping wells of mineral water are also located along the thrusts. Wells of Siwon Semmul, Daejeong Eumryo and Jain Guanguang mineral water producing companies are drilled in different aquifers. However, the wells of Chungsoo Eumryo and Hanjoo Sikpoom are drilled in the same aquifer, and are influenced each other during pumping. To understand hydrogeological characteristics, field hydraulic tests (slug and pumping tests) were conducted in wells of the five companies. Pumping and slug test data were interpreted using several models to get best solution. For slug test, Cooper-Bredehoeft-Papadopulos, Bouwer &Rice, Hvorslev methods were used. In slug test, the calculated values of transmissivity and storativity by C-B-P method's range from 6.60E-3 to 3.23E-8 m2/sec, from 0.1 to 1E-10, respectively. Hydraulic conductivities by Bouwer &Rice and Hvorslev method range from 1.03E-4 to 7.47E-8 m/sec and from 1.15E-4 to 9.45 E-8 m/sec, respectively. As the models of pumping test, Hantush's "Wedge-shape confined aquifer model" (1962) and Moench-case 1 leaky-aquifer model" (1985) were adequate for the most cases. The pumping test models match well with geological information that indicates wedge-shaped aquifer. From the pumping test, the estimates of transmissivity and storativity by Hantush's and Moench-case 1's methods range from 1.23E-1 to 2.87E-6 m2/sec, from 1.34 E-1 to 2.27E-8 m2/sec, respectively.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....9511H