Evaluation of thermotolerant coliforms and salinity in the four available water sources of an irrigated region of Southern Sri Lanka
2003
Shortt, R. | Boelee, Eline | Matsuno, Y. | Faubert, G. | Madramootoo, C. | Hoek, Wim van der
In many developing countries a close linkage exists between drinking and irrigation water; however, the effects of irrigation management on drinking water availability and quality, and what drinking water supplies are best suited to irrigated areas, have been little studied. Bacterial contamination and salinity of drinking water sources in a community within the Uda Walawe irrigation system of southern Sri Lanka were monitored from August to December 2000. Water with the lowest combination of faecal contamination and salt content (highest quality) was found in shallow wells, recharged with seepage water from the irrigation system. Of these wells, those surrounded by a protective wall had the lowest levels of thermotolerant coliforms (median of 244 ThCU 100 ml-1) as compared to shallow wells without protective walls (549 ThCU 100 ml-1). Furthermore, tube well waters were highly saline (average of 0.67 mS cm-1), while canal and reservoir waters had high thermotolerant coliform levels (3940 and 950 ThCU 100 ml-1). Interseasonal canal closures eliminate the canals as a water source, lowering water levels in shallow wells, and thus reducing regional water availability. Concrete lining of canals may exacerbate the drying up of shallow wells during canal closure, therefore eliminating the primary source of water in the region that can be used for drinking after only simple treatment.
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