Sharp Interface Approach for Regional and Well Scale Modeling of Small Island Freshwater Lens: Tongatapu Island
Abstract
:1. Introduction
2. Materials and Methods
2.1. Study Area
2.2. Sharp Interface Freshwater-Seawater Groundwater Flow Numerical Model
2.2.1. Governing Equations
2.2.2. Conceptual Model for Groundwater Flow in Tongatapu Island
2.3. Calibration of the Model
2.4. Long-Term Stresses
2.4.1. Impact of the Current Pumping
2.4.2. Impact of Long-Term Stresses
3. Results
3.1. Results of Calibration
3.2. Current State of Freshwater Lens and Impact of Current Pumping
3.3. Predicted Effects of Long-Term Stresses
3.3.1. Impact on Freshwater Lens
3.3.2. Well Salinization
4. Discussion
5. Conclusions
Supplementary Materials
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Sl.No | Scenario | Recharge (m/year) | Pumping from Public Wells (m3/day) |
---|---|---|---|
1 | Base (current) | 0.570 (R) | 10,410 (P) |
2 | 0.69 R | 0.393 | 10,410 |
3 | 0.65 R | 0.371 | 10,410 |
4 | 0.60 R | 0.342 | 10,410 |
5 | 1.6 P | 0.570 | 16,656 |
6 | 1.8 P | 0.570 | 18,738 |
7 | 2.0 P | 0.570 | 20,820 |
Parameters | Values |
---|---|
Number of observation points | 16 |
Correlation coefficient | 0.87 |
Range in observations | 8.23 m |
Maximum residual | 2.65 m |
Minimum residual | −2.84 m |
Residual mean | 0.27 m |
Absolute residual mean | 1.15 m |
Root mean squared error | 1.44 m |
Normalized RMS error | 13.8% |
Scaled RMS error | 17.5% |
Parameters | Current Pumping | Predevelopment | Percentage Decrease | |
---|---|---|---|---|
Maximum freshwater head (m) | 0.329 | 0.347 | 5.19 | |
Minimum interface elevation(m) | −13.72 | −14.46 | 5.12 | |
Freshwater thickness (m) | Maximum | 14.05 | 14.81 | 5.13 |
Average | 8.40 | 9.02 | 6.87 | |
Area (km2) where lens thickness is | >5 m | 206.5 | 208.2 | 0.79 |
>7 m | 167.3 | 170.8 | 2.08 | |
>10 m | 83.1 | 91.7 | 9.39 | |
Volume (MCM) of freshwater where lens thickness is | >0 m | 636.7 | 658.4 | 3.30 |
>5 m | 581.4 | 604.7 | 3.86 | |
>7 m | 510.1 | 536.9 | 5.00 | |
>10 m | 294.8 | 334.6 | 11.90 |
Sl.No | Scenario | Percentage of Wells Intruded by Saltwater | Maximum Saltwater Ratio |
---|---|---|---|
1 | Base (current) | 0.0 | 0.00 |
2 | 0.69 R | 5.1 | 0.004 |
3 | 0.65 R | 38.5 | 0.13 |
4 | 0.60 R | 51.3 | 0.22 |
5 | 1.6 P | 12.8 | 0.05 |
6 | 1.8 P | 38.5 | 0.24 |
7 | 2.0 P | 53.8 | 0.35 |
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Babu, R.; Park, N.; Yoon, S.; Kula, T. Sharp Interface Approach for Regional and Well Scale Modeling of Small Island Freshwater Lens: Tongatapu Island. Water 2018, 10, 1636. https://doi.org/10.3390/w10111636
Babu R, Park N, Yoon S, Kula T. Sharp Interface Approach for Regional and Well Scale Modeling of Small Island Freshwater Lens: Tongatapu Island. Water. 2018; 10(11):1636. https://doi.org/10.3390/w10111636
Chicago/Turabian StyleBabu, Roshina, Namsik Park, Sunkwon Yoon, and Taaniela Kula. 2018. "Sharp Interface Approach for Regional and Well Scale Modeling of Small Island Freshwater Lens: Tongatapu Island" Water 10, no. 11: 1636. https://doi.org/10.3390/w10111636