| Daguhe River, which is the largest river in Jiaodong Peninsular and the main drinking water source for Qingdao city, supplies with drinking water totaling 80 million cubic meter annually, which dominates about 45 percent of the municipal water supply. With the city development and water utilization increase, water environment in the Daguhe River source field is more and more important. In this paper, a groundwater quality numerical model is built to predict the groundwater pollution in Daguhe River source field based on hydrogeological and environmental geological investigations and field tests.This paper will cover the following five parts. Part I, the concept and application of numerical modeling are introduced briefly. Part II, the regional geology and hydrogeology are discussed comprehensively and concisely. Part III builds a groundwater flow numerical model. Part IV builds a groundwater quality numerical model. Part V the groundwater pollution is predicted based on numerical models.The Daguhe River water source field spans an area of 436. 8 km2 with a scope of north to Guxian-Pumu and south to Qingdao-Jiaozhou expressway. In the initial mining stage, the groundwater type is predominantly HC03 ?Cl-Ca, with a relatively high concentration of F in some western parts of the Daguhe River. After years of mining, the chemical composition changes rapidly. In the northern part, the groundwater type transforms into HC03 ?S04, Cl ?HC03, Cl ?S04~Ca or CaMg, even N03 locally. In the middle part, the water quality changes slowly with a type of HC03 ?SO HC03 ?Cl-Ca. While in the southernpart, the concentrations of pollution elements ascend annually, the dominant type is HC03 ?S04 ?Cl-Ca with S04 ?Cl or S04-CaMg locally. Due to Ligezhuang mining cone which caused salt water intrusion, groundwater quality aggravates severely and the mean elements over national proof standard (GB) are SO/", Cl", totle dissolved solids, totle hardness, N03". S042" increases annually.In this paper, the horizontal two-dimensional hydrodynamic-dispersion equations are introduced in this groundwater quality numerical model. And the solution of the model can be divided into two processes. Firstly the seepage equation is solved and the advection-dispersion equation follows secondly. The initial groundwater flow field level is based on December 31 1989 data in situ and interpolation. The study area of total 436. 8 km2 is divided into three parts and 12 regions based on aquifer rock feature. The initial concentrations in groundwater quality model are interpolated from field data in June 1995. Four elements of Cl"> N03\ S042\ N02~are considered. Based on regional hydro-metro logical condition, 10 time segments are calibrated. The pollution (Cl N03~> N02") in the source field can be divided into point and surface kind. The surface pollution comes from chemical fertilizer over utilization, river water pollution and dispersal of living waste water. While the source pollution results from industrial waste water dispersal.Using the above mentioned numerical models, water quality is predicted from 2003 to 2012 in Daguhe River groundwater source field. The results are as follows:1) N02 concentration predictionThe pollution trend of N02 in study area is mitigating, while in the lower reach of Ligezhuang Township the pollution aggravates.Although the present protection measure is considered, N02 concentration is still beyond national standard III for groundwater quality. Groundwater conservancy measures should be enhanced further. All dispersals of pollution sources are over national standards should be ceased. On the other side, agricultural planting structure and fertilizer dispensation technology should be improved; the chemical fertilizer use should be decreased gradually.2) Cr concentration predictionThe pollution trend of CF in study area is mitigating. The concentration of Cl" is above national standard III, while in the lower reach of Ligezhuang Township the pollution aggravates. The construction of anti-seepage wall which loc... |
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