Streamflow Prediction of Cañas River Watershed, Cavite, Philippines using Long Short-Term Memory

Cavite is a highly urbanized province situated near Metro Manila and has the highest population growth rate in the country. Water resource management and water-related risk mitigation is one of the major challenges the province faces. Cañas River Watershed is one of the major river systems in the province which covers major cities and municipalities. Effective streamflow monitoring in this watershed has not been achieved due to the inadequacy of monitoring stations around the province. This study aimed to develop an LSTM model to predict the streamflow in Cañas River Watershed at the Panaysanayan river gauge using the available weather parameters in two weather stations in the province, namely: Sangley Point Synoptic Station and Cavite State University (CvSU) Agrometeorological Station. Using the short-term data dated from 2014 to 2019 obtained from the stations and the river gage, the Long Short-Term Memory (LSTM) model successfully predicted the streamflow. Based on the model performance evaluation the values of Nash-Sutcliffe Efficiency (NSE) for the training and test were 0.90-0.91 and 0.87-0.89, respectively which indicates a high predictive accuracy. On the other hand, the Percent Bias (PBIAS) results in training and testing ranges 0.60% -8.04% and 1.92% -8.32%, respectively, which indicates a low bias prediction. The model tends to underestimate values, especially high magnitude flows. The RMSE-to-Standard Deviation Ration (RSR) results in training and testing ranges from 0.30-0.31 and 0.34-0.35, respectively, which indicates a good predictive power. The model results also show a good performance in developing a flow duration curve in the river to determine its dependable flow. The R2-value between the observed and predicted flow at different probability of exceedance is 0.9938. The dependable flow of Cañas River Watershed at Panaysanayan river gauge was 60 liters per second based on the observed flows and 61.12 liters per second based on the predicted flows.