Analysis of Anti-Intrusion of Saline Water Well Using Sunjoto’s Method

Abstract

Coastal area was a place which are occupied since the beginning of civilization movement caused by this place contain fresh water especially in the sandy beach. In this area fresh water can be exploited easily by swallow dug well. But in modern era, this place changes become dense population area and as a consequent the saline water intrusion occurs due to the extraction of fresh water. The saline water intrusion occurs in many places of Indonesia for example it reaches the area of Monas in Jakarta, the saline water intrusion in city of Merauke caused by the over drainage of swamp area. This problem occurs when groundwater storage decrease caused by the decreasing of rain water infiltration to the ground and the exploitation groundwater increases. According to Ghijben-Herzberg relationship that the border of saline water and fresh water will increase about 40 times of decreasing groundwater surface and as a consequent the groundwater storage changes become brackish or salty. This system was proposed as a model of anti-saline water intrusion well which was called ‘Coastal Fresh Water Optimal Well’ which was tested in Biak island, and they proved that this design is appropriate for the coastal area fresh water withdrawal but there is not computation of this system. In this paper the sustainability design can be analyzed using parameters of depth of fresh water storage and up coning. Up-coning depends drawdown and drawdown depends on discharge of pumping, coefficient of permeability of soil and shape factor of well.