Numerical Analysis of Migration of Nitrate Ions in the Groundwater System of Lake Karachai Area, Southern Ural, Russia

The groundwater pollution in the area of Lake Karachai, southern Ural, Russia, stemmed from liquid waste disposal in the lake, has been monitored using over 200 boreholes allocated to surrounding area, and various studies have been made for the evaluation of environmental effects in collaboration with international activities (Drozhko et al. 1997; Rumynin et al. 1998). Referring to the works of Russian researchers (Rumynin 2011, and others) on monitoring and hydrogeological and numerical analyses, we tried to unravel macroscopically the hidden hydrogeological structure and hydraulic parameters which formed the monitored distribution of NO3- in the subsurface region of this area. Using an integrated terrestrial surface-/subsurface-coupled flow simulator, we set 6 possible conceptualized field 3-D models with different hydrogeological structures regarding the shape of rock boundary and existence/nonexistence of faults. In addition, for each model, we set 3 different K-d (distribution coefficient of concentration on the solid surface and in water). Comparing the calculated pattern with the observed distribution patterns of NO3-, we found that the adsorption parameter Kd might be in the order of around 0.5 L/kg and that the values of the porosity and hydraulic conductivity of shallow lava prospected by the Russian researchers might be consistent for approximating the subsurface condition in this area.