Presentation Information
[O12-P03]Analysis of Groundwater Salinization and Countermeasure Evaluation Using a Model Experiment
*Yuito Mizuno1 (1. Aichi Prefectural Toyota Nishi High School SS Science Club)
Keywords:
Salinization,Global warming,Model device
1. Background
Groundwater is a vital water resource used for domestic and agricultural purposes. However, particularly in coastal areas, “groundwater salinization”—the intrusion of seawater into groundwater aquifers—has become a significant problem. As salinization progresses, the salinity of the water increases, diminishing its value as a water resource. A report by the Ministry of Land, Infrastructure, Transport and Tourism indicates that excessive groundwater extraction has led to groundwater-related issues such as land subsidence and salinization. In recent years, sea-level rise associated with global warming has emerged as a new factor of concern, and there is a possibility that salinization will progress further in the future. Therefore, this study aimed to reproduce the mechanism of groundwater salinization using a model apparatus for the purpose of visualization and understanding.
2. Objectives
The objective of this study is to clarify, through model experiments, the conditions under which groundwater salinization occurs and progresses, and to examine the impact of sea-level rise caused by global warming on salinization.
3. Methods
To simulate a groundwater environment, we constructed a small transparent model apparatus and conducted experiments using freshwater and saltwater. In the initial setup, saltwater was added after filling the apparatus with freshwater; however, the freshwater flowed out of the apparatus, preventing the accurate simulation of an actual groundwater environment. This was attributed to the failure to account for the fact that groundwater is retained within the pores of soil, sand, and gravel. Therefore, we improved the setup by incorporating a gravel layer to create a structure where water is retained within the voids. Additionally, assuming a scenario where freshwater continuously flows from the landward side to the seaward side, we attempted to reproduce the “brine wedge” formed by the density difference between the water flow and the brine. For this experiment, we received guidance from Professor Masayuki Ishii of Shimane University.
4. Results
In the improved model apparatus, we observed that denser saltwater intruded from beneath the freshwater, resulting in the formation of a saltwater wedge. This result is consistent with the actual mechanism of groundwater salinization. On the other hand, we also found that the saltwater wedge disappeared within a short time once the water flow stopped.
5. Discussion
These results suggest that the flow of freshwater and the density difference between it and saltwater play a significant role in groundwater salinization. Furthermore, it is highly likely that salinization will be accelerated as sea-level rise makes it easier for saltwater to intrude.
6. Summary and Outlook
In this study, we successfully reproduced and visualized groundwater salinization and saltwater wedges using a model apparatus. Moving forward, we intend to conduct further research on measures to suppress salinization by examining structures that maintain water flow and by modifying the freshwater-saltwater interface.
Groundwater is a vital water resource used for domestic and agricultural purposes. However, particularly in coastal areas, “groundwater salinization”—the intrusion of seawater into groundwater aquifers—has become a significant problem. As salinization progresses, the salinity of the water increases, diminishing its value as a water resource. A report by the Ministry of Land, Infrastructure, Transport and Tourism indicates that excessive groundwater extraction has led to groundwater-related issues such as land subsidence and salinization. In recent years, sea-level rise associated with global warming has emerged as a new factor of concern, and there is a possibility that salinization will progress further in the future. Therefore, this study aimed to reproduce the mechanism of groundwater salinization using a model apparatus for the purpose of visualization and understanding.
2. Objectives
The objective of this study is to clarify, through model experiments, the conditions under which groundwater salinization occurs and progresses, and to examine the impact of sea-level rise caused by global warming on salinization.
3. Methods
To simulate a groundwater environment, we constructed a small transparent model apparatus and conducted experiments using freshwater and saltwater. In the initial setup, saltwater was added after filling the apparatus with freshwater; however, the freshwater flowed out of the apparatus, preventing the accurate simulation of an actual groundwater environment. This was attributed to the failure to account for the fact that groundwater is retained within the pores of soil, sand, and gravel. Therefore, we improved the setup by incorporating a gravel layer to create a structure where water is retained within the voids. Additionally, assuming a scenario where freshwater continuously flows from the landward side to the seaward side, we attempted to reproduce the “brine wedge” formed by the density difference between the water flow and the brine. For this experiment, we received guidance from Professor Masayuki Ishii of Shimane University.
4. Results
In the improved model apparatus, we observed that denser saltwater intruded from beneath the freshwater, resulting in the formation of a saltwater wedge. This result is consistent with the actual mechanism of groundwater salinization. On the other hand, we also found that the saltwater wedge disappeared within a short time once the water flow stopped.
5. Discussion
These results suggest that the flow of freshwater and the density difference between it and saltwater play a significant role in groundwater salinization. Furthermore, it is highly likely that salinization will be accelerated as sea-level rise makes it easier for saltwater to intrude.
6. Summary and Outlook
In this study, we successfully reproduced and visualized groundwater salinization and saltwater wedges using a model apparatus. Moving forward, we intend to conduct further research on measures to suppress salinization by examining structures that maintain water flow and by modifying the freshwater-saltwater interface.