Abstract:
Purpose: Large diameter agro-wells are the most valuable water resources for farmers in Mahaweli
system H in Sri Lanka to sustain crop production during the dry spells. Deterioration of water quality is
harmful to the crop growth. Present study evaluated the variation of irrigation water quality and water
levels of agro-wells in Thalawa irrigation block of Mahaweli system H.
Research Method: Water samples from 10 agro-wells were collected during October 2016 to July 2017
once in a month and tested samples for irrigation water quality parameters using standard methods.
Water levels were recorded for each sampling date.
Findings: Most of the water quality parameters tested in almost all wells are within the acceptable
range for irrigation except for Residual Sodium Carbonate (RSC). 50 % of the wells are safe and rest
50 % of the wells are within marginal range in terms of RSC. Irrigation water quality index (IWQI) was
assessed and it varied from 32.6 to 87.7. Considering the mean IWQI (48.2), water of Thalawa block can
be characterized as good. The study also revealed that there was suffi cient water in wells even during
the dry spells and it varied with both the variation of rainfall and canal water availability.
Research Limitations: Sampling was limited to 10 agro-wells for a period of 10 months. This was
avoided by selecting representative wells and months covering both dry and wet spells.
Originality/ Value: Overall, results envisaged that there is higher potential to use this water for any crop
and soil without detrimental to crops grown.
Keywords: Agro-wells, Irrigation Water Quality, Mahaweli System, Water quality index
