The Iloilo River
THE ILOILO RIVER is located between N 10°41’30” –N10°42’30” Latitude and E 122°32’00” – 122°35’00” Longitude. Iloilo River flows from west to east, with an estimated specific sediment discharge rate of 8.0 cubic meter per year per square kilometer, and a catchment area of 93.1 square kilometer.
The river is between a barrier beach and an alluvial plain formed by its tributaries. It receives its freshwater supply from tributaries discharging from the north and run-off from the nearby agricultural lands. Two of its major tributaries, with channel lengths of 5–6 km, are Calajunan Creek and Dungon Creek.
During high tide, seawater from Iloilo Strait flows into the Iloilo River affecting the salinity of the river, both vertically and horizontally. Since the river is relatively flat, with a gentle gradient of 1:4000, seawater can move upstream encompassing all six of the sampling stations used in this study. The velocity of the river during high tide was measured at 0.52m/s.
The Department of Environment and Natural Resources (DENR) classifies the Iloilo River as a Class C Water. It is intended for the propagation and growth of fish and other aquatic resources, for secondary recreational activities (e.g. boating), and is also an industrial water supply for manufacturing processes after treatment (DENR-DAO No. 34, 1990). It supports varied species of fauna such as fish, birds, and crustaceans and flora including mangroves and plankton.
However, based from physico-chemical properties, the water quality of the river has deteriorated over the years since treated and untreated sewage have been discharged into the river by several waste generators that are located along the riverbanks and its tributaries.
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