SUMMARY

Assessment of salt intrusion distribution, vulnerability and some mitigated solutions
for salt intrusion of unconsolidated aquifers in Central coastal region' plains

Phạm Quý Nhân, Tạ Thị Thoảng, Trần Thành Lê, Phạm Thị Thu, Nguyễn Thế Chuyên

In context of unpredictable climate change, salt water intrusion is top concern to Vietnam coastal areas in general and central coastal region where there exists extreme climate condition and water supply demand’s increase for socio-economic development in particular. Ground water resources with high potential are Quaternary unconsolidated aquifers. In order to clarify the current status of salt intrusion, we applied reviewing method for previous studies, the geophysical method in addition with sampling and analyzing water samples from boreholes and dug wells to delineate salt-fresh water interface, GIS and mapping to zone salt intrusion vulnerability. The method GALDIT for assessment of salt intrusion vulnerability is applied in association with determining a weighting of each indicator by Analytical Hierarchical Process (AHP). The results shown that ground water salt intrusion of Quaternary unconsolidated aquifers have changed in recent years. Assessment and zonation of salt intrusion vulnerability of Quaternary aquifers in central coastal region has been clarified. In Northern area, high vulnerability occupies more than a half area of plain (56.8% about 4,061.8 km²) while in Southern area, high vulnerability occupies almost areas of plain (63.3%, about 5,724km²). Based on current status of salt intrusion and zonation of salt intrusion vulnerability of Quaternary aquifers we recommend some mitigated solutions which were verified for effectiveness and impacts by numerical modeling and analytical solutions. Some mitigated solutions which are recommended are infiltration basin, barrier wall and pumped well discharge optimization.

Keywords: Salt intrusion, vulnerability, climate change, unconsolidated aquifers, Central region coastal plain