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8. Applications of Groundwater Quality Models
A Study of the Mathematical Modeling for Groundwater
Contamination in Xi'an City
The purpose of this study was to build a groundwater quality model based
on the observed data of chlorine ions. The model was then used as a tool for
analyzing and predicting the tendency of groundwater contamination in that
city. Another purpose of the study was to explore the feasibility of building a
regional water flow model and water quality model using the long-term
observation data.
In the first stage, the data of hydrogeology and environmental hydrogeology were collected, analyzed and synthesized. This work was completed
by the First Hydrogeological Brigade of Shaanxi Province, China, which
provided necessary preparations for building the water quality model.
Through a great amount of work, both in the laboratory and in the field, the
following data were obtained:
1. The descriptions of regional geologie and hydrogeologie conditions, including the distribution of the phreatic aquifers and their thickness,
hydraulic conductivities, storativities and hydraulic relationships with adjacent aquifers;
2. The distribution, quantity and utilization of the wells; the distributions of
sewerages, waste-water reservoirs and polluted ponds; the historical and
the present situation of sewage irrigation;
3. The original hydrochemical background in the groundwater and the present state of pollution; the types and sources of contaminants in the area;
4. The long-term data (from 1954 to 1959) about chlorine pollution in the
groundwater shows that the historical pollution of the groundwater was
caused by city sewage, while the current pollution is generated by sewerage irrigation;
5. The historical records of water levels and water extraction. The maps of
water level contours for two hydrological years (from 1978 to 1980) were
compiled, and researches on the historical changes of the groundwater
flow field in Xi'an City were also conducted.
In the second stage, a groundwater flow model of the Xi'an City was
developed. The simulated area was 570 km 2 and was divided into 195 triangular elements. The simulation model was solved by the multiple cell balance
method. It was impossible to make effective pumping tests to determine
the hydrogeologie parameters in such a large region, so the calibration of
the flow model could only rely on the long-term observation data. Through
simulating water level changes in two years (from April 1978 to April 1980),
hydraulic conductivity K, specific yield Sy, coefficient of rainfall infiltration A
in 9 subdomains, and seepage Q from sewage reservoirs and ponds were
obtained by solving the inverse problem. Then, a steady flow field and the
distribution of average velocities were computed, in wh ich the velocities were
obtained indirectly by Darcy's law.
8. Applications of Groundwater Quality Models
A Study of the Mathematical Modeling for Groundwater
Contamination in Xi'an City
The purpose of this study was to build a groundwater quality model based
on the observed data of chlorine ions. The model was then used as a tool for
analyzing and predicting the tendency of groundwater contamination in that
city. Another purpose of the study was to explore the feasibility of building a
regional water flow model and water quality model using the long-term
observation data.
In the first stage, the data of hydrogeology and environmental hydrogeology were collected, analyzed and synthesized. This work was completed
by the First Hydrogeological Brigade of Shaanxi Province, China, which
provided necessary preparations for building the water quality model.
Through a great amount of work, both in the laboratory and in the field, the
following data were obtained:
1. The descriptions of regional geologie and hydrogeologie conditions, including the distribution of the phreatic aquifers and their thickness,
hydraulic conductivities, storativities and hydraulic relationships with adjacent aquifers;
2. The distribution, quantity and utilization of the wells; the distributions of
sewerages, waste-water reservoirs and polluted ponds; the historical and
the present situation of sewage irrigation;
3. The original hydrochemical background in the groundwater and the present state of pollution; the types and sources of contaminants in the area;
4. The long-term data (from 1954 to 1959) about chlorine pollution in the
groundwater shows that the historical pollution of the groundwater was
caused by city sewage, while the current pollution is generated by sewerage irrigation;
5. The historical records of water levels and water extraction. The maps of
water level contours for two hydrological years (from 1978 to 1980) were
compiled, and researches on the historical changes of the groundwater
flow field in Xi'an City were also conducted.
In the second stage, a groundwater flow model of the Xi'an City was
developed. The simulated area was 570 km 2 and was divided into 195 triangular elements. The simulation model was solved by the multiple cell balance
method. It was impossible to make effective pumping tests to determine
the hydrogeologie parameters in such a large region, so the calibration of
the flow model could only rely on the long-term observation data. Through
simulating water level changes in two years (from April 1978 to April 1980),
hydraulic conductivity K, specific yield Sy, coefficient of rainfall infiltration A
in 9 subdomains, and seepage Q from sewage reservoirs and ponds were
obtained by solving the inverse problem. Then, a steady flow field and the
distribution of average velocities were computed, in wh ich the velocities were
obtained indirectly by Darcy's law.