The objective of this study was to assess the contamination from nitrates and ammonia of
drinking water in Nepal. The data was collected and analyzed in Nepal from
groundwater and surface water sources for four weeks in January of 2000.
Nitrate contamination in Nepal is much more prevalent at shallow depths due to
anthropogenic sources. Nineteen percent of the wells sampled shallower than 50 feet
were contaminated with nitrates above the World Health Organization (WHO) limit of 10
mg/L NO3
There were no wells deeper than 100 feet that were contaminated with
nitrates above the WHO guidelines. Ammonia contamination is minimal in shallow
wells. However, high ammonia concentrations exist deep in the aquifers due to the
geologic depositions of peat and lignite beds.
Nitrate contamination in Nepal is more common in urban areas than in rural agricultural
regions. The average concentration of nitrates from urban drinking water sources is 3.9
mg/L NO3
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-N. However, the average concentration in rural areas is only 1.2 mg/L NO3
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- N. There are many urban anthropogenic sources of nitrate contamination in Nepal such
as poorly designed septic systems and inadequate containment and treatment of sewage.
The primary rural anthropogenic source of nitrates in groundwater is from agricultural
fertilizers. The lack of rural nitrate contamination is possibly a seasonal result of reduced
infiltration and surface run-off during the dry season. Both dry-season and monsoon
season sampling must be performed to verify if agricultural nitrate concentrations are
consistent year-round.
In addition, nitrate concentrations are relatively low in supplied and treated water
sources. These sources include water that is treated at water treatment plants and
supplied though piped networks to large urban centers and tube wells, most of which
have only recently been installed. However, nitrate concentrations in traditional water
sources were very high. Traditional water sources are those sites that have been used as
drinking water sources for hundreds of years such as water spouts and hand-dug wells.
The average nitrate concentration in traditional water sources was 7.6 mg/L NO3
but the average nitrate concentrations in supplied water sources was only 1.9 mg/L NO3