Evaluating the estuarine tidal discharge through water stage component analysis and in-situ measurement - Case study Mandovi-Zuari estuary of Goa, India

Abstract

Determining tidal reach and long-term monitoring of tidal discharge are vital in an estuarine system due to their potential use in water resource management and inland navigation. The upstream river discharge contributes to the nonstationary and nonlinear features of estuarine discharge. The tidal reach of an estuary can be identified based on the tidal influence on its water stage components. In the present study, a novel approach based on the Hilbert-Huang transform (HHT) and complete ensemble empirical mode decomposition with adaptive noise (CEEMDN), is used to decompose water stages into several Intrinsic mode functions (IMF). Those IMFs with different amplitudes and periodicities represent those factors that influence the water stages in an estuary. The efficiency of the present method is analyzed with the measured water level data from the estuary of Mandovi-Zuari in Goa, India. Principal ocean lunar semidiurnal constituent M2 is found to be the major tidal constituent, which is consistent in the coastal region. Subsequently, the high-frequency discharge is computed and validated with direct discharge measured by Rio Grande Acoustic Doppler Current Profiler (ADCP). Post-monsoonal discharge is computed using pre-monsoonal calibration coefficients, and a strong correlation is found between post-monsoonal measured and computed discharge. The proposed study will be helpful to estimate reliable estuarine tidal discharge with minimum operational maintenance.