The Intrusion of Geothermal Water into Domestic Groundwater in Chiang Mai Basin, Northern Thailand

Abstract

The similarity in chemical species of some domestic groundwater in the eastern part of Chiang Mai basin and thermal spring water were noticed during the illvestigatiol~ for the cause of fluorol.oxicosis in Northern Thailand. The major elements except silica such as sodium, fluoride, calcium, magnesium and iron are showing t.he same trend and against. those of normal groundl·mter. The effect areas located parallel to t.he Hae Tha fault zone and show the direction intercept ,with thermal spring system. The intrusion of thermal water into these domestic groundwater were suggested via underground fractures and faults which related to the thermal spring system.

The isotopic study show the contaminated water have their isotopic ratio trending toward the thermal spring water indicated the origin of these water similar to those of thermal springs but at a lower mixing ratio.