Simulating streamflow in the Santa Rosa River in Laguna, Philippines
2010
Ramos, L.T., Philippines Univ. Los Baños, College, Laguna (Philippines)
A GIS [Geographical information system] event-based rainfall-runoff model that predicts streamflow on a catchment scale was developed and parameterized using biophysical attributes of an urbanizing catchment which drains into the Santa Rosa River in Laguna province, Philippines. The model solved discharge using the Newton-Raphson method through the kinematic wave approach. PCRaster modeling language was used to implement the model. Primary data inputs required to run the model were stream network, stream width, roughness, digital elevation model (DEM), catchment area, surface cover, soil type, roughness coefficients, gravitational water height, saturated hydraulic conductivity and rainfall. Surface cover was delineated using supervised classification of an Aster L1B image. Surface soil samples were collected, their gravitational water capacity and saturated hydraulic conductivity were determined. Rainfall was measured using two tipping bucket rain gauges with loggers. A 5-meter water level logger was installed in the Macabling Irrigation Dam for measuring discharge height. The calibrated model predicted discharge and water height with a coefficient of determination, r square = 0.774 and a Nash-Suteliffe efficiency index, NS = 0.776. After validation through sensitivity analysis, scenarios of urban and forested land use change were simulated driven with a rain storm event. The model can be used to generate scenarios showing the relationship between rainfall, land use change and streamflow response and thus aid in land use planning.
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