Hydrodynamic analysis of the inner part of the Gulf of Nicoya, Costa Rica: Updating field measurements for coastal users

Although extensively studied, the inner region of the gulf of Nicoya (one of the main estuaries of Costa Rica) has a relatively low amount of research focused on its hydrodynamic. This represents a limitation for establishing hydrodynamical models and doing complex analysis of the water movement, which are vital for the proper management of the multiple economic, social, and ecological actors present at the estuary. The aim of this study is to generate and update hydrodynamic and bathymetric data of the inner region of the Gulf of Nicoya, with measurement periods and temporal resolutions that could be used for better understanding the hydrodynamic patterns and the development of future numerical models. Water level, current velocity, and bathymetry were measured in two separate field surveys, almost two weeks each, during dry and rainy seasons. Time series of each variable were collected with temporal resolutions of 20 min or less. Pressure and acoustic gauges were used for measuring the variables in representative sites of the hydrodynamics of the estuary. The measured data supports the hydrodynamic pattern described in previous studies, but shows some differences derived from the longer and finer data series. The most inner part of the estuary presents a time lag of up to 25 min and 30% amplification of the tide wave in comparison to the estuary’s entrance. Maximum currents show values of 1.3 m/s, and mostly around the change of tides, there are moments in which bottom and superficial currents flow in almost opposite direction with velocities less than 0.2 m/s. Bathymetry shows various areas where the new and historical data do not coincide. The present study contributes to update and extend the available data on hydrodynamic related variables, delivering updated time series with higher temporal resolution for future numerical models and general analysis from other coastal users.