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Contamination of Nitrate in Shallow Aquifers: A case study in Jaffna District, Sri Lanka Contamination of Nitrate in Shallow Aquifers: A case study in Jaffna District, Sri Lanka

Congress: 2008
Author(s): Thushyanthy Mikunthan, Cristena Shanthi De Silva
Department of Agricultural Engineering Faculty of Agriculture, University of Jaffna, Sri Lanka Department of Agricultural and Plantation Engineering Faculty of Engineering Technology, The Open University of Sri Lanka

Keyword(s): contamination of nitrate,shallow aquiferspollution, quality of groundwater
AbstractConcern has been expressed recently about the increasing levels of nitrate-N in the groundwater at the Jaffna Peninsula. Groundwater is the lonely accessible water resource in addition to seasonal rainfall for all the purposes in the Peninsula. The groundwater is the most natural resource and perhaps its quality constitutes dissolved or contaminated nutrients within the water due to natural processes and human activities. Contamination of nitrate into the groundwater is also occurs by natural and human activities. The quantity of fertilizers used for agricultural purpose by the Jaffna farmers has been boosted in double fold over the years and attempts have been made to study the effect of large scale use of fertilizers on groundwater. A preliminary investigation was done to determine the nitrate-N content in groundwater in the Jaffna district, Sri Lanka in different usage of well such as public well, domestic well, water supply scheme well and Agriculture well. Forty wells were randomly selected in Jaffna district with three water supply wells. Another forty wells were selected from two intensified agricultural areas in the study area. Groundwater samples were collected from March 2007 to six consecutive months during driest months at monthly interval. The nitrate- N concentration was ranged from 0.5 mg/l to 24.0 mg/l. Out of randomly selected wells, 30 % of public wells, 12 % of domestic wells and 85% of the farm wells exceeded the limit of WHO recommendation level of 10 mg/l. In purpose sampling in intensive agricultural area all the wells except 2.5% of wells had problem of contamination of nitrate-N. The results indicated that there was a high rate of leaching of nitrate due to intensive agricultural practices. The nitrate-N content was higher than the permissible level of WHO for drinking water in farm wells. Using recommended quantities of organic and inorganic fertilizers, encourage the use of substitution levels of chemical fertilizers whenever organic manures are used, usage of efficient irrigation water, long term monitoring of quality of well waters in this region are suggested as recommendations. Contamination of nitrate -N is definitely in the shallow aquifers and making it is unsuitable for human consumption and irrigation. Continuous monitoring and quality assessment in well water are necessary to avoid the quality hazards to the people in the area. Since the origin is known, elimination of the source of nitrogen contamination may be the best corrective measure. The efficient management of groundwater is imperative since this resource is a key factor for all the purposes in the Peninsula.
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