Abstract:
Walawe river, which is located in Ambalantota, belonging to dry zone of Sri Lanka is highly
exploited for domestic and irrigation purposes. Seawater intrusion in the river adversely affect
the livelihood of bordering communities by hindering freshwater availability and salinization of
agricultural lands. Present study determined the level of salinization in Walawe River and its
impacts on associated agricultural lands (paddy) during the dry season where the salinization is
profound. Data collection was carried out during the period from March to April, where water
samples were retrieved from 50 locations along the river starting from the river mouth to 8 km
upstream, and salinity levels were examined. Soil samples (n=44) of immediately adjacent
agricultural lands were collected from random transects (n=10; length=200 m) which were placed
perpendicular to the river, starting from the shoreline. Such that 4-5 soil samples were collected
along each transect at 50 m interval. Physicochemical properties of soil samples; salinity, pH,
organic matter content, moisture content, nitrate concentration and phosphate concentration were
measured. Current status of agricultural productivity was evaluated employing a questionnaire
survey using 30 farmers. Salinization through river water, seepage of saline water through river
banks and direct spray were identified as major causes of salinization in adjacent agricultural
lands. Salinity of the river water ranged from 0.17 to 5.95 ppt (maximum level recorded at the
mouth) while soil salinity ranged from 0.10 to 0.44 ppt. Significant correlation was not observed
between soil salinity and other physicochemical parameters (Spearman’s rank; P>0.05). Further,
significant variations were also not observed between variables (Kruskal-Wallis; P>0.05).
Findings suggest that at present the impact of salinity has no significant effect on the
physicochemical properties of soil and productivity of associated agricultural lands. However,
continuous long-term studies are required to assess the long-term salinization effects.
