State of water environmental issues
3. Sea Area
3.1.1. Water resources in general
Cambodia's coastal zone can be conceptualized as being made up two inter-related systems, namely, (i) the ecological system which includes the physical, chemical and biological environment that provides natural resources, sequesters pollutants and offers fundamental life-support functions (clean air and water, etc) for humans and other living-organisms; and (ii) the socio-economic system which depends on the many functions and products of the ecological sub-system.
Ecological systems have abundant but limited capacity to provide saline aquatic life, including fish, and clean water as well as other resources to meet the demand of the socio-economic system. It is not surprising that the final demands by society and new opportunities for multiple uses are the source of increasing conflicts within the coastal zone. Cambodia's coastline is currently being subjected to various stresses, for example, mangrove deforestation, coral reef/sea-grass destruction, marine aquaculture, and others.
Cambodia's coastal shoreline is 435 km along the Gulf of Thailand. The seaward boundary of the coastal zone has been delimited as the outer limit of the Exclusive Economic Zone (EEZ) with an area of 55,600 km². The landward boundary of the coastal zone has not yet been satisfactorily defined, but is temporarily considered to be about five kilometres from the shore. The coastal zones are situated in the Koh Kong and Kampot provinces, and in the Sihanoukville and Kep towns. Sihanoukville is the largest town on the coast that has deep seaport facilities and is considered to be one of the economic centres of Cambodia.
The coastal climate differs from other areas in the country. Its climate is also tropic monsoon with an annual rainfall between 2,000 and 4,000 mm. Generally, during the wet season from May until November the rainfall is largely derived from the southwest monsoon drawn landward from the Indian Ocean, while the dry season, which commences from November and lasts until April, is associated with the northeast monsoon which sends drier and cooler air throughout the region.
This amount of rainfall is higher than other areas in the country. The area has average wind speeds of two to four m/s and temperatures varying from 27.5 to 28.5 degrees Celsius. Generally, the minimum temperature is 19 degrees Celsius in December while the maximum temperature is 35 degrees Celsius in April. As a natural condition, the coast has tides per day with amplitude of 1.5 m and approximate surface currents of 0.2-0.7 miles per hour. Wave amplitudes of two to three metres during the rainy season and 0.25 to 0.50 during the dry season are not uncommon.
3.1.2. Water environment in general
All the rivers that flow into the Gulf of Thailand are relatively small with water levels changing significantly according to the volume of rainfall. Rivers in the coastal areas are very short and have their sources in hills about 500 to 600 m in altitude. They flow between hills and fall in cascades before reaching the plains that are located 15 to 20 km from the sea. In the delta areas, the rivers divide into estuaries where the levels of turbidity are usually high and there are several marsh areas covered by mangrove forests.
There are many rivers and streams located in the coastal area, which usually dries up in the dry season. The sea influences most of the rivers in the coastal zone. In the dry season, the low-lying parts of the rivers are saline.
Pollution of the rivers or streams in the coastal zone in Cambodia is mostly caused by deforestation, industrial and domestic wastes, aquaculture activities, fuel stations, and cargo ports, as well as oil terminals and ship yards. However, the level of pollution in the coastal area in Cambodia is not high.
The oxygen concentration of the surface water remains almost stable; in the early part of the dry season, saturation at the surface water is between 102 and 104 percent and dissolved oxygen (DO) fluctuates from 4.2 to 4.8 ppt. Phosphorus on the surface water is mosaic in character during the dry season, varying from 0 to 2 ppb; this value remains the same to the bottom. In the wet season, phosphorus concentrations of the surface water vary between 0.1 to 3.8 ppb and increase slightly at the bottom.
Recently, there has been some information available on suspended solids in the marine water in Cambodia. This information was collected from other provinces and municipalities surrounding the Cambodia coastal zone.
There is some information available for heavy metal concentrations in the coastal water in Cambodia. Recently, surveys and monitoring programmes regarding marine water quality in the coastal areas have been conducted.
- Table of contents > 3. Sea Area
- 3.1. Introduction
- 3.2. Coastal ecosystems
- 3.3. Coastal resources
- 3.4. Other Natural Wonders
- 3.5. Fisheries
- 3.6. Oil and Gas
- 3.7. Salt pans
- 3.8. Medical plants
- 3.9. Threats to marine environment
- 3.10. Threats to the coastal environment