THESIS APPROVAL

Environmental Conditions in the Lower Chao Phraya River
1. General Information
The lower Chao Phraya river is an important estuary located in Bangkok and
Samutprakarn Province. This estuary occupied the area approximately 58 km
extending from the mouth of the river to Rama VII Bridge. The mouth of the river is
opened to the upper Gulf of Thailand. Water change in this area was controlled by
diurnal tides. The volume and salinity of water are mainly affected by influence of
precipitation, freshwater and seawater. The bottom of the estuary was constituted of
fine sediment mainly composed of mud.
2. Water Qualities and Sediment Properties
The Office of Environment Policy and Planning (2001) reported that water
qualities in the lower Chao Phraya river were in rather bad condition. Most of all
parameters were within the Thailand National Water Quality Classification for
industrial purpose, except for DO, biochemical oxygen demand (BOD) and ammonianitrogen
(NH3-N) which declined below the criteria. The measurement of water
quality recorded during 1994 and 1999 for DO, BOD and NH3-N were 1.6, 3.2 and 1
mg/l, respectively.
It is obvious that the rapid increase in population and coastal development lead
to water quality change. Ngamprayad (1999) found that the frequency of low DO
tends to be greater in urbanized and industrialized zones. Pollution sources, such as
urban runoff, sewage disposal, and industrial effluents, contribute to the loading of
organic pollutants to the water and bottom sediment of the estuary (Wattayakorn,
2003). According to Pollution Control Department (2000), the average BOD loading
from domestic waste in Chao Phraya river was approximately 19-1,377 mg/l while the
industrial loading estimated 230-29,000 mg/l. It is evidence that the industrial activity
was the major source of organic matter in this area followed by the domestic waste.
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