Abstract:
The chemistry of surface waters and groundwater
draining agricultural catchments in the north-central and
northwestern areas of Sri Lanka is described. Hydrochemical
data from 296 water samples are used to evaluate water quality
and to identify the processes that control nitrate and phosphate
concentrations in the water. The results indicate that nutrient
concentrations in the groundwaters are greater than those in
the surface waters. Increased nutrient levels were observed in
groundwater in a selected area in the fortnight following fer tilizer application. Detailed geochemical investigations of
selected groundwater samples reveal a gradual rise of nitrate–
N and other solutes along the horizontal flow direction.
Compared to the application rates of fertilizer in the area, the
average nutrient concentrations in all waters are relatively low
(1.5 mg/l nitrate and 0.5 mg/l phosphate) and stable. The
results suggest that prevailing reducing conditions, iron-rich
overburden soil cover and manmade canal networks control
nutrient accumulation in the groundwater
