9. A New Statistical-Empirical Hybrid Based Model to Estimate Seasonal Sea-Level Variation in the Gulf of Paria from River Discharge

The study presents new insight into the quantitative role of the world’s third largest discharging river, the Orinoco of South America as modulating coastal water levels in the vicinity of its outflow. The case study is in a semi-enclosed sea, the Gulf of Paria, located in the southern extreme of the Caribbean Sea. The discharge – coastal water level relationship has been investigated and the water levels exhibit a high correlation (R² = 0.92) to the trends in actual discharge. The relationship is non-linear and there is a lower threshold value across the months of the year below which the water levels are characterised by large variability around a mean linear trend showing independence of the Orinoco’s discharge. There is also an upper threshold value where the maximum amplitude of variation is 21.4 cm. The study utilises a vertically integrated 2D numerical modelling suite to execute a series of experiments to ascertain the variation of the coastal water levels from the variation in the river discharge. The other drivers are wind, salinity, oceanic currents and tidal forcing. The results are finally utilised to develop a third order model function to estimate the average monthly river-driven water level in the Gulf of Paria dependent only on the parameter of river discharge.