Groundwater evolution beneath Hat Yai, a rapidly developing city in Thailand |
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Authors: | A Lawrence D Gooddy P Kanatharana W Meesilp V Ramnarong |
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Institution: | (1) British Geological Survey, Wallingford, Oxfordshire, OX10 8BB, UK,;(2) Environmental/Trace Analysis Research Unit, Prince of Songkla University, Hat Yai, Thailand,;(3) Department of Mineral Resources, Ministry of Industry, Ratchathewi, Bangkok 10400, Thailand, |
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Abstract: | Many cities and towns in South and Southeast Asia are unsewered, and urban wastewaters are often discharged either directly
to the ground or to surface-water canals and channels. This practice can result in widespread contamination of the shallow
groundwater. In Hat Yai, southern Thailand, seepage of urban wastewaters has produced substantial deterioration in the quality
of the shallow groundwater directly beneath the city. For this reason, the majority of the potable water supply is obtained
from groundwater in deeper semi-confined aquifers 30–50 m below the surface. However, downward leakage of shallow groundwater
from beneath the city is a significant component of recharge to the deeper aquifer, which has long-term implications for water
quality. Results from cored boreholes and shallow nested piezometers are presented. The combination of high organic content
of the urban recharge and the shallow depth to the water table has produced strongly reducing conditions in the upper layer
and the mobilisation of arsenic. A simple analytical model shows that time scales for downward leakage, from the surface through
the upper aquitard to the semi-confined aquifer, are of the order of several decades.
Electronic Publication |
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Keywords: | conceptual models contamination groundwater quality Thailand urban groundwater |
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