Analysis of Seawater Intrusion Based on Conductivity Method and Hydro-Chemical Approaches to Shallow Coastal Wells in Alluvial Plains of Kendal Regency, Central Java

Abstract

Kendal Regency is one of the regencies in Central Java which has 0.64% of population growth and 1.023/km2 of population density per year. Kendal Regency is also known as Industrial Area. On other hand, Regional Drinking Water Company (PDAM) has increased in demand every year, and mostly being used for household needs. These indicates that there is less surface water supply in Kendal Regency. As a result, there are negative effects such as lowering the ground water level, decreasing the quantity and quality of ground water, and seawater intrusion. This research was made to determine the distribution of seawater intrusion in the coastal areas of Kendal Regency. The method used in this research was to find the value of Electrical Conductivity in well water. And then, the well water was tested using hydro-chemical test to determined the cause of intrusion in the research area by projecting on the Trilinear Piper diagram. This research was conducted in 7 districts in Kendal Regency which are located in 38 shallow well points in coastal area. The result shows that the values of Electrical Conductivity have range of 436 μS/cm to 5.083 μS/cm. based on these results, the well water in this research area can be classified into fresh water, fresh-brackish water, and brackish water. The analysis using Trilinear Piper diagram can be concluded that the saltiness of the well water in the research area are occurred due to seawater intrusion.