Report on the environmental isotopic investigations in Lower Kelantan River Basin, Malaysia (Part 3)

A pilot project on isotope hydrology of the Lower Kelantan Basin was undertaken since March 1980. The principal objective of this project is to develop isotope hydrological techniques as an investigational tool and to complement work by conventional methods at the Geological Survey of Malaysia and universities in Malaysia. The overall aim of these investigations is to study the groundwater movement, recharge areas, direction and flowrate and also to identify the recharge mechanism of the existing aquifers. The isotopic data demonstrates that the groundwater is recharged locally through precipitation. Low tritium values observed in the second and third aquifer suggest that the groundwater in these aquifers comprises an old water component. As a whole, these three aquifers are interconnected in places and regionally they may be considered as representing a single system. This was evidently shown by small variations in their isotopic contents; with the first aquifer being unconfined, while the second and third are semi-confined. Trituim data confirmed that all groundwater samples on the third aquifer are older than 25 years and most waters from the first and second aquifers are younger than 25 years. Consequently a few selected samples from the third aquifer were analysed for 14C concentrations in an attempt to determine the age of the groundwaters. The 14C results show that their age ranges from 2000 to 11000 years old. All deep wells and most of the wells located near the Kelantan River do not seem to receive any river water contribution whatsoever. However, it seemed that the shallow wells at a few locations were affected by river water unfiltration to a certain extent. Some important findings that have emerged from this study will be very useful in the planning of the implementation of groundwater management in Malaysia, in particular the Kelantan Basin