Spatial and Temporal Variations of the Stratification of Salinity and Suspended Solids in Iloilo River Estuary

The spatial-temporal variations of salinity and total suspended solids (TSS) were determined in the Iloilo River Estuary during the wet (October to December, 2014) and dry (January to March, 2015) seasons. The salinity and water temperature were measured using the YSI Pro 230 probe in ten sampling sites along the river from surface to bottom at ebb and flood tides. Results showed that salinity varied vertically and horizontally having the highest value downstream and lowest upstream. Lower values of surface to bottom salinity were observed at ebb tide and higher values were observed at flood tide. During the wet season, the salinity was lower compared to the dry season. These results, as expected, showed that salinity depends and varies through seasons, tidal periods, and location along the Iloilo River Estuary. On the other hand, water temperature was increasing from upstream to downstream at ebb tide and decreasing values observed at flood tide for both the wet and dry seasons. Water samples were also collected for TSS determination in each sampling site. The samples were decanted and air-dried and then TSS was measured. The analyses showed that the amount of TSS was higher during wet season and lower during dry season. The difference is attributed to urban-runoff, high flow rates, soil erosion, and dredging which increases the TSS level during the wet season. Moreover, these factors affected the TSS level in each sampling location. Thus, such activities along the Iloilo River Estuary may contribute to the amount of TSS present in the river.