Abstract
A drinking-groundwater source protection technology system based on a three-dimensional finite-difference groundwater model was constructed and applied to the safe management of drinking groundwater in the first terrace of Fujiang River. In the study area, the main type of groundwater is the quaternary systemic alluvial deposit loose rock pore water and the aquifer thickness varies between 20 and 35 m. Groundwater is the main source of water and is used for various purposes through two exploitation wells. The water volumes of 1# exploitation well (1#) and 2# exploitation well (2#) are 10,000 m3/day and 5000 m3/day, respectively. An analysis of 22 indicators from 11 groundwater samples showed that a higher concentration of chemical-oxygen-demand (CODMn) and ammonia–nitrogen (NH3–N), and they had a high correlation with most of the other water-quality factors. Therefore, CODMn and NH3–N were selected as indicator factors for model calibration and prediction. Twenty-two hydraulic head observation wells were used for flow-model calibration. The flow model indicated that a drop funnel formed with a maximum depth of 12 m, and the particle-capture zone in the original downstream direction of the south side extended to 1100 m because of groundwater exploitation. The solute-transport model showed that industrial pollution sources were the main factors that led to a deterioration of water quality. To analyze the necessity and effectiveness of remediation measures for the safety of drinking-water sources, two scenarios were considered to predict the concentration of NH3-N and CODMn in groundwater exploitation wells over 20 years. Scenario I, which considered that current conditions were maintained, predicted that the NH3-N would exceed the drinking-water quality standard of 0.5 mg/L after 16 years. Scenario II, in which industrial sewage treatment plants were installed outside the particle-trapped zone of the exploitation wells and strict anti-seepage measures were implemented, predicted that the peak concentrations of NH3-N and CODMn in the exploitation wells would be 0.26 mg/L and 1.33 mg/L, respectively, after 3 years of model operation. This study provides a theoretical basis for drinking-groundwater source protection that can be applied to safety management practices.
Highlights
A drinking-groundwater source protection technology system based on a three-dimensional finitedifference groundwater model was constructed and applied to the safe management of drinking groundwater in the first terrace of Fujiang River
The monitoring results show that the factors in the surface water samples are far below the Class-III standard, which means that recharge of Fujiang River will not influence the groundwater drinking function (Table 3)
This study indicates the increased safety risks of drinking-water sources because of a variation in the surrounding environment that is caused by anthropogenic activities
Summary
A drinking-groundwater source protection technology system based on a three-dimensional finitedifference groundwater model was constructed and applied to the safe management of drinking groundwater in the first terrace of Fujiang River. The solute-transport model showed that industrial pollution sources were the main factors that led to a deterioration of water quality. To analyze the necessity and effectiveness of remediation measures for the safety of drinking-water sources, two scenarios were considered to predict the concentration of NH3-N and CODMn in groundwater exploitation wells over 20 years. Scenario II, in which industrial sewage treatment plants were installed outside the particle-trapped zone of the exploitation wells and strict anti-seepage measures were implemented, predicted that the peak concentrations of NH3-N and CODMn in the exploitation wells would be 0.26 mg/L and 1.33 mg/L, respectively, after 3 years of model operation. No previous studies have been conducted on the drinking-groundwater source safety risk caused by rapid urbanization and more frequent anthropogenic engineering activities in the study area. Few studies have been conducted using groundwater numerical models to construct a drinking-groundwater source safety-management system with an input-feedback-decision section
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