Effects of surface water infiltration on groundwater Fluoride concentration close to an irrigation take : A case study in Polonnaruwa district.
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Date
1998-11-07
Authors
Dharmagunawardhane, H. A.
Wikramasooriya, A. K.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya
Abstract
A problem of growing concern is the excessive concentrations of fluoride found in
many dug wells and water supply bore holes in the low plains of the Dry Zone, notably in the
Anuradhapura and Polonnaruwa districts. The fluoride concentration in many of these wells
exceed 1.5 mg/l and pose a health hazard to the consumers. There is in these areas, wide
prevalence of dental fluorosis specially among children of school going age. The slow rate of
groundwater movement and higher evapo-transpiration in the low plains of the Dry zone tend
to increase the fluoride concentration.
Within the areas of high fluoride bearing groundwater, it is still possible to find
certain areas especially close to irrigation tanks, with considerably low fluoride
concentrations with regard to the safe limits of drinking water standards. Since surface water
contain low fluoride concentrations compared to ground water, dilution of groundwater by
infiltration of surface water from the irrigation tanks could be a major governing factor for
this situation.
The possible effects of surface water infiltration on fluoride content of ground water
was studied in the Polonnaruwa district, in a small village situated below the major irrigation
tank; Parakrama Samudra. The behavioral patterns of the groundwater table and groundwater
fluoride content revealed that the concentration of fluoride in groundwater of the area is
controlled by the infiltration of the surface water from the tank and the irrigation channel. It
was found that the fluoride of groundwater is low in the vicinity to the surface water bodies
especially in the down-slope sides. Fluoride concentration increases in the direction of
groundwater flow and away from the surface water bodies within the area of influence of the
surface water.
On account of the widely spread surface water irrigation network in the Polonnaruwa
district, it could be expected that the low fluoride areas close to irrigation tanks and channels
are a result of infiltration and dilution of fluoride content by the surface water.
Description
Keywords
Fluoride concentration , Groundwater , Irrigation , Energy and environmental sciences
Citation
Proceedings & Abstracts of the Annual Research Sessions,1998,University of Peradeniya, peradeniya, Sri Lanka, pp 26