Summary of Groundwater Quality in Cambodia
– Data, Maps, and Priority Parameters
Resource Development International Cambodia August 2009 Updated March 2011 Updated March 2012
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Summary of Groundwater Quality in Cambodia
Background – Groundwater and Drinking Water in Cambodia
Tube wells (also known as boreholes) and open wells (also known as dug wells) are common throughout Cambodia (see Well Types page) and provide rural Cambodians with groundwater for drinking, cleaning, bathing, and agricultural activities. The quality of the water these sources provide can vary depending upon the presence of natural and human-caused contaminations. Deeper wells are often safer from the impacts of human activity at the surface but may have a higher risk from contaminations that are naturally found in the ground. These contaminations can cause health problems or may make the water taste or look bad. Shallow wells can be safer from naturally-occurring contaminates like Arsenic, but have a higher risk from contaminations associated with human activity at the surface, such as faecal waste. Surface waters and shallow aquifers can become contaminated when rains wash through faecal waste and subsequently through or along the ground. Because there is little human and animal waste management in Cambodia, surface waters (rivers, streams, lakes, and ponds) and shallow groundwaters are usually contaminated with faecal pollution (microorganisms such as viruses, bacteria, and protozoa). However, harmful microorganisms called pathogens are much more easily removed (boiling, ceramic/bio-sand filtration, disinfection) than chemical contaminants such as Arsenic, Manganese, Fluoride, Nitrate, and Iron. Rainwater is also heavily relied upon in Cambodia and is often the preferred water source because of its look and taste. If stored well and in sufficient quantities, rainwater can provide the safest and most reliable source for drinking water in rural Cambodia. Piped water systems are also emerging in areas where population density and general wealth are sufficient to sustain these systems
Groundwater Quality
Since 2005, RDI has been conducting groundwater surveying activities from province-to-province, collecting samples and analyzing them in our laboratory. Over 10,000 wells have been tested in five priority provinces. Some areas have been found to have unsafe levels of Arsenic, Manganese, Fluoride, and Nitrate which can cause serious impacts to human health. Many areas have high Iron, Turbidity, Hardness, etc. which do not impact human health but may make the water taste and look bad, damage clothes, or cause rice to turn colour when cooked. The following sections present general water quality conditions and trends observed as part of these surveying activities.
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Drinking Water Quality Index - Health
A drinking water quality index (DWQI) has been developed in order to present groundwater risk at the commune level. The DWQI health represents the chance of deeper groundwater being safe for consumption in a commune. For example, an index of 68 for a particular commune means that there is a 68% chance that a tube well drilled in that commune will be safe. Therefore, a score of 100 is very good while a 1 is a very poor. This index is based on the well points surveyed by RDI and the analysis of Arsenic, Manganese, Fluoride, and Nitrate – 4 common health-impacting groundwater contaminants. Figure 2 presents the health DWQI for each commune in Kandal, Prey Veng, Kampong Cham and Kampong Chnang.
A DWQI score is not reported for communes where less than 5 samples were collected. In some communes, wells may not have been present or they were inaccessible at the time when field technicians visited the area.
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Arsenic
Arsenic is the most critical chemical groundwater contaminant in Cambodia because it affects a very large area and has the most severe health consequences for those consuming arsenic contaminated water for a long time (generally 5 to 10 years). Long-term consumption can cause various internal cancers and visible manifestations on the hands and feet, known as hyperkeratosis. Arsenic concentrations in Cambodia have been found as high as 3000 ppb where the WHO and Cambodian drinking water quality standards are 10 ppb, and 50 ppb, respectively. Figure 3 presents areas where Arsenic has been observed to be elevated in the groundwater.
However, Arsenic is sometimes found above the drinking water standards in locations away from the rivers and this is still a cause for concern. Also, in the Arsenic impacted areas, there is a much greater risk for high concentrations in deeper tube wells as opposed to shallower dug wells.
More detailed Arsenic information including province, district, commune breakdowns are provided in the Groundwater Summary Tables here.
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Manganese
Manganese is another health-impacting groundwater contaminant that has been found in Cambodia. Like Arsenic, Manganese is naturally present in the ground. Manganese contamination effects many wells in Cambodia but the health effects are less visible than Arsenic. Manganese is called a neurotoxin which means it can affect the function of the brain. Some studies have linked Manganese groundwater consumption to lower test scores and hyperactivity in children. The Cambodian and WHO drinking water standard for Manganese is 0.4 mg/L for health impacts. Manganese at lower concentrations can cause unpleasant water and discolouration of cooked rice but is safe to drink. Figure 4 presents areas where Manganese has been observed to be elevated in the groundwater.
Manganese concentrations are very high throughout Kean Svay District in Kandal Province but elevated concentrations exist in small pockets throughout the surveyed area.
More detailed Manganese information including province, district, commune breakdowns are provided in the Groundwater Summary Tables here.
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Fluoride
Fluoride is commonly added to the water supply in developing countries because at certain concentrations it can have dental hygiene benefits. However, naturally-occurring Fluoride in the groundwater is sometimes present at very high concentrations and this can cause dental and skeletal problems. The Cambodian and WHO drinking water quality standards for Fluoride are 1.5 mg/L. It has been found that concentrations greater than 4 mg/L can cause skeletal fluorosis which can cause very serious health effects. Figure 5 presents areas where Fluoride has been observed to be elevated in the groundwater.
More detailed Fluoride information including province, district, commune breakdowns are provided in the Groundwater Summary Tables here.
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Nitrate
Nitrate is present naturally in the ground but only at low concentrations. Elevated concentrations are typically associated with human disturbances such as improper human and animal waste management or heavy fertilizer usage. Small-scale animal raising is common in Cambodia and if fecal waste is not managed properly, Nitrate levels can be very high in nearby wells. High Nitrate levels can cause a blood disorder known as blue-baby syndrome or methemoglobinemia in infants under 6 months of age. The lips and finger tips of the infant may turn purple/blue and in severe cases the condition is fatal. Figure 6 presents areas where Nitrate has been observed to be elevated in the groundwater.
Elevated concentrations of Nitrate are generally very localized and the result of poor human or animal waste management around the well. Note that the map above is for tube wells only and open wells are much more susceptible to Nitrate contamination because they are shallower. However, pockets of aquifer contamination have been found in northern Prey Veng Province, Sithor Kandal District. This condition is present because of a combination of factors; there are many tube wells in the villages, nearly all are very shallow (10 to 20 metres), the population density is high, cows and pigs are commonly raised under houses, and waste management practices are poor.
More detailed Nitrate information including province, district, commune breakdowns are provided in the Groundwater Summary Tables here.
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Iron
Iron concentrations are generally very high in the groundwaters of Cambodia. Iron is naturally-occurring but has no health effects when consumed through drinking water. Iron can cause the water to look cloudy, taste poor, and can stain laundry or discolour rice. The drinking water quality standard for Iron is 0.3 mg/L based on aesthetic effects, but this is often exceeded in groundwaters. Figure 7 presents areas where Iron has been observed to be elevated in the groundwater.
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