Abstract:
Sustainable water resources management requires monitoring and assessment of
water quality in addition to quantity. Coastal lagoons play a critical role for the peo ple and the ecosystem at large. Water quality monitoring and assessment for lagoons
in Sri Lanka is important considering its services to the country. However, due to a lack
of resources, most of the lagoons are not monitored and reported properly for further
action. This study aims to develop a protocol in terms of monitoring sites, parameters,
and frequency for water quality monitoring using a case study in a coastal lagoon, in
Sainthamaruthu, Sri Lanka. The physicochemical parameters were measured weekly at
eighteen monitoring sites for 4 months during the dry season from June to September
2022. Cluster analysis (CA) along with Inverse Distance Weighted (IDW) interpolation
technique revealed that a minimum of three sites out of 18 are sufficient for mon itoring water quality in the lagoon. In light of Principal Component Analysis (PCA)
and Discriminant Analysis (DA), it was decided to retain temperature, pH, turbidity,
Total Dissolved solids (TDS), Electrical Conductivity (EC), and Dissolved Oxygen (DO)
in monitoring programs, since they cumulatively account for 79% of the variation in
water quality in the lagoon spatially and temporally. Monitoring turbidity, TDS, and EC
at weekly interval, while monitoring temperature, pH, and DO at biweekly or monthly
is recommended. A further indication of the lagoon’s water quality is that the mean
values for turbidity (27 NTU), EC (754 µS/cm), and DO (4.6 ppm) higher than ambient
standards, while TDS (344 ppm) and pH (6.98) are within. Therefore, we conclude that
the lagoon requires remediation measures to be suitable for environmental purposes
during dry periods.
