Dr. Narayan Pd Upadhyaya, Rosha Raut, Nirita Giri

Kathmandu valley is believed to be a lake in pre historic period. According to folklore, a monk named Manjushree came for meditation in the valley and made an outlet by splitting a hill to drain out the water from the valley. After this the valley became suitable for human settlement and the civilization started in Kathmandu. During that time, water was plentiful but with increase in population, the available water became insufficient and people started to search new sources by constructing well and stone spout. With time as the city grew, people faced the shortage of water' the river water was deteriorating due to haphazard urbanization and industrialization and the volume of required water was increasing. In addition the sealing of ground by buildings and roads decreased the ground water level consequently drying up the stone spouts, once a major source for water. As a result water from different sources such as rivers, springs etc were piped into the valley from periphery areas such as Sundarijal, Budhanilkantha, Dudhkhola while some people extracted water from deeper ground.

The current pipe water supply demand in Kathmandu valley is about 150MLD but the combined supply from ground and surface water in dry season varies between 65 and 85 MLD. As the surface water yield is crucial during the dry season, a policy of conjunctive use of ground and surface sources has been implemented. On an average the contribution of the ground water remains close to 50% of the total supply.

Ground water is an important source of water for the inhabitants of the Kathmandu valley as majority of the residents depends on this source. Ground water is usually less contaminated than surface water. Leachate from agriculture field, underground sewage storage tanks, landfills, abandoned hazardous wastes, industrial wastes storage lagoons etc. located above or near aquifers usually the cause of ground water contamination. Once ground water becomes contaminated, cleansing itself from degradable wastes as surface water is almost impossible. Ground water flow is slow and non-turbulent thus contaminants are not effectively diluted and dispersed. Furthermore, Ground water has only small population of decomposing bacteria than surface water systems reducing rate of purification.

Objectives
The main objective of the study is to know the ground water quality of Kathmandu valley. Hence, only some major parameters like Ammonia, Iron, Nitrate, and Manganese were selected to know whether the water quality is suitable for the domestic use or not.

Area of study
Kathmandu valley representing the cities of Kathmandu, Bhaktapur and Lalitpur is the study area. Altogether 95 ground water samples were analyzed from various points of the Kathmandu valley during the year 2003. The sampling sites were selected randomly from different public and private ground water sources viz. tube well, dug well, deep boring.

Results & Discussion
The analyzed results of different parameters have been compared with WHO guideline values for drinking water. The percentage of ground water sources having the concentration of ammonia, nitrate, iron and manganese greater than WHO GV for drinking water at the time of analysis are shown in the table below.

Total no. of samples	Kathmandu	Lalitpur	Bhaktapur
	70	19	6
	Percentage contaminated
NH3	52.86	47.37	83.33
NO3	11.43	31.58	16.67
Fe	65.71	47.37	50.00
Mn	24.29	31.58	23.33

Minimum values of NH3, NO3, Fe and Mn found in Kathmandu, Lalitpur and Bhaktapur are represented in the table and graph as follows:

	NH3 (mg/L)	NO3 (mg/L)	Fe (mg/L)	Mn (mg/L)
Kathmandue	0.01	0.05	0.05	0.01
Lalitpur	0.05	0.14	0.03	0.01
Bhaktapur	1.3	0.05	0.05	0.14
WHOGV	1.5	50	0.3	0.1

Significance of Ammonia, Nitrate, Iron and Manganese in water
Iron is a common element present in minerals and soil and hence most natural water contains some dissolved iron. The guideline value of Iron as recommended by WHO is 0.3mg/L. The problems created by high iron concentrations are mainly aesthetic. Clothes develop rust stains when washed in water containing iron. It also leads to corrosion of pipes, pumps etc and may lead to the deposition of Ferric hydroxide.

Ammonia is an indicator of water pollution through human activities and natural decay processes. Sewage contains large amount of ammonia due to bacterial decay of nitrogenous organic wastes. Presence of ammonia in ground water is mainly due to seepage of wastewater but in case of deep ground water, it is due to geological factors like quality clay and so on. The guideline value of Ammonia as recommended by WHO is 1.5mg/L. Higher concentration of ammonia is harmful for fish and other biota and even human beings.

The most important source of Nitrate in water is the biological oxidation of organic nitrogenous substances, which come in sewage and industrial wastes. Some of the major sources of Nitrate in water are domestic sewage, fertilizers, rainwater and manure. The guideline value of Nitrate as recommended by WHO is 50mg/L. Higher concentration of Nitrate in water may cause death in infants by cyanosis. Nitrate concentration higher than 200mg/L increase the risk of stomach cancer.

The guideline value of Manganese as recommended by WHO is 0.1mg/L. At levels exceeding 0.15mg/L, manganese in water supplies stains plumbing fixtures and laundry. At 0.05mg/L, manganese will often form a coating on pipes, which may slough off as a black precipitate.

Conclusion

The study shows that most of the ground water in Kathmandu valley is contaminated with Iron and Ammonia and to some extent Manganese also. Presence of Iron and ammonia in high concentration might have been due to geological condition. It might have leached out from the aquatic plants, which might have been deposited during prehistoric times.

For domestic consumption of water, most of the water should be treated for the removal of these parameters. Though the parameters are only of aesthetic significance, it is always better to treat them if they are above WHO guideline value because excess is always harmful.