Sediment trap, Bacuit Bay, El Nido (photo: R Rollon)

Data for watershed and plume modelling

Researchers Bayosa Aya Carino-Valdez from the University of the Philippines Marine Science Institute, Dr. Rene N. Rollon from the Institute of Environmental Science and Meteorology, and Engr. Bryan Hernandez from the College of Engineering travelled to El Nido in August. Their mission was to gather current data and to set up monitoring instruments for future data collection that will be used to calibrate watershed and plume models under development in Component 1.

The purpose of the fieldwork was to examine four major watersheds and their coastal areas, and to establish sites at two rivers for longer term measurement of discharge. The team visited watersheds in Barangays Barotuan, Bucana, New Ibajay, Pasadena and Manlag observing their size, surrounding land use, and other distinct conditions.

Water samples were collected to compare the flow and suspended sediment of contributing tributaries with the main river outlets.

Sediment traps were installed in five locations and will be retrieved later this year to measure the volume of sediment deposits.

Engr Bryan Hernandez (left) and Bayosa Aya Carino-Valdez (right) measuring flow in Brgy New Ibajay, El Nido (photo: R Rollon)

Stilling wells have been installed in Brgys Manlag and Barotuan. These contain water level sensors which will be used to analyse river discharge. Light sensors were also attached to the set-up to assess turbidity. River flow was measured using an electromagnetic flow meter and stream cross-section was measured to get volumetric flow and discharge.

A rain gauge and barometric pressure sensor were also installed in Manlag.

The team plans to return to the study sites in November to gather data collected by the instruments installed.

When completed, the watershed model will indicate sediment load transported from land under different levels of vegetation cover to seagrass meadows, mangroves and coral reefs. The plume model will be used to determine the extent, intensity and frequency of the plumes, particularly in the dry and wet seasons, to see how sediment is retained and dispersed to coastal ecosystems.