This paper gives an overview of the geophysico-chemical groundwater conditions in Sri Lanka and the associated contemporary management challenges. Groundwater is extensively used in Sri Lanka today, for agriculture, domestic use and industry/tourism. Groundwater access, availability and vulnerability are governed by six major types of aquifer systems of which the most prevalent is the regolith aquifers in the central hard rock areas of the island. Uncontrolled groundwater use and contamination or natural poor quality are leading to access limitations and health concerns. The tsunami severely affected groundwater in the coastal areas and functioned as a wake-up call to further emphasize the importance of groundwater for life-supporting functions. Despite an emerging awareness, groundwater management is in its infancy, with the attitude of groundwater development still not converted into an approach of active management. The role of groundwater in achieving sustainable development and in the development of appropriate water management institutions needs to be highlighted and specifically addressed in policy discussions.

The Valigamam region is underlain by a Miocene limestone formation and a highly porous soil cover. The region is totally dependent on groundwater to meet its agricultural, industrial and domestic needs, since other sources of water are seasonal. Recharge from rainfall is limited by high run-off and evapotranspirational losses. The region experiences water supply problems due to high concentrations of chloride, total hardness and nitrate in groundwater. The spatial distribution of chloride varies from year to year, with maximum concentrations experienced during or after the wet season. The major factor explaining high chloride concentrations is the excessive extraction of groundwater that results in saline intrusion from the sea or tagoonal areas. In a large proportion of wells sampled for nitrate, levels exceed the WHO standard due to intensive agricultural practices involving very high inputs of artificial and natural fertilizers and the improper construction of latrine soakaway pits. To improve groundwater quality in the Jaffna Peninsula will require controls on the location of new wells, a revision of existing and future pumping rates and a change in agricultural practices. It is imperative that future work in the region should focus on combining groundwater management and sustainable agricultural practice.

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This study was done to describe the association between source of drinking water and other potential risk factors with dental fluorosis. Prevalence of dental fluorosis among 518 14-year-old students in the south of Sri Lanka was 43.2%. The drinking water sources of the students were described and fluoride samples were taken. There was a strong association between water fluoride level and prevalence of fluorosis. Tea drinking before 7 years of age was also an independent risk factor in a multivariate analysis. Having been fed with formula bottle milk as an infant seemed to increase the risk although the effect was not statistically significant. No clear effects could be found for using fluoridated toothpaste, occupation of the father, and socio-economic status. Drinking water obtained from surface water sources had lower fluoride levels (median 0.22 mg l(-1)) than water from deep tube wells (median 0.80 mg l(-1)). Most families used shallow dug wells and these had a median fluoride value of 0.48 mg l(-1) but with a wide range from 0.09 to 5.90 mg l(-1). Shallow wells located close to irrigation canals or other surface water had lower fluoride values than wells located further away. Fluoride levels have to be taken into account when planning drinking water projects. From the point of view of prevention of dental fluorosis, drinking water from surface sources or from shallow wells located close to surface water would be preferable.

Unprotected open dug wells of shallow groundwater environments are subjected to high risk of chemical and microbial pollution in many parts of the world. The present study was initiated in Pungudutivu, one of the surrounding islands of the Jaffna Peninsula, Sri Lanka, because the island totally relies on its limited groundwater resources extracted from open dug wells to meet all its needs. The study assessed the risk of pollution within the limited fresh groundwater found in unconfined aquifer systems of Pungudutivu, where high risk of pollution was expected mainly from organic sources, derived from human and animal wastes and easy infiltration and runoff returns. The fresh groundwater pockets of Pungudutivu were however found to be with less serious contamination risks other than high Fe 2+ and high faecal coliform counts. Low nitrate and phosphate concentrations with high COD and low BOD demonstrated less pollution from biodegradable organic sources in the midst of high oxidising potentials in the shallow dug wells as implied by the stability field of Fe(OH) 3 on the Eh-pH diagram; the argument of high Fe 2+ in groundwater however, wasn't supported by the said oxidation potential. High faecal coliform counts with high DO in groundwater probably indicated conditions implied by on site waste disposal in groundwater of Pungudutivu.