Development of monthly seawater intrusion vulnerability assessment
method using GALDIT
Abstract
Accurate diagnoses of vulnerability of seawater intrusion (SWI) into
aquifers are required to ensure sustainable utilization of groundwater
resources in coastal areas. GALDIT was selected to assess the SWI
vulnerability on western coastal areas of South Korea. Climate change
trends are updated every year. The existing GALDIT method has various
scores to express the changing observed values. However, they are
limited because of their sensitivity in the assessment of regional
characteristics or climatic change due to low weight flexibility.
Therefore, this study assessed vulnerability to SWI by classifying the
existing GALDIT into static and dynamic parameters. The static
parameters include groundwater occurrence (G), aquifer hydraulic
conductivity (A), and distance from the shore (D), whereas the dynamic
parameters include height to groundwater level above sea level (L),
impact of existing status of seawater intrusion (I), and aquifer
thickness (T). The monthly mean was used as the dynamic index to reflect
monthly variations. To indicate the temporal trend of parameter L was
calculated based on the data observed at the sea level station adjacent
to the groundwater level station. To sensitively reflect the monthly
changes in values, the range of scores was divided into 10 parts. The
calculated GALDIT index showed that the most vulnerable month was
September. In the progress of SWI, vulnerability was assessed monthly to
highlight the differences in parameters that fluctuate seasonally. The
proposed method can be used to apply intensive countermeasures to
vulnerable sites and build an operation plan considering the
vulnerability period.