San Juan Bay Estuary Tides – Las Mareas en el Estuario de la Bahía de San Juan, Puerto Rico

After over a year of recording water levels in the San Juan Bay Estuary, I was finally able to develop models for some of the water bodies. Models include tidal harmonics and precipitation inputs. Harmonic components for each water body were calculated using the TideHarmonics package from A.G. Stephenson in the R programming language. These components were then loaded into a Google sheet, where I then translated the predict.tide function (also from A.G. Stephenson) into javascript. This allows me to compute new tide tables everyday for each water body. Precipitation inputs were modeled using an exponential moving average of hourly rainfall data from the San Juan International Airport. Historical times uses recorded rainfall and future times use forecasted rainfall. This data is collected hourly from the Wunderground API system. Each waterbody responds to precipitation differently, depending largely on its tidal connectivity – more tidal water bodies show less of a precipitation response, and vice a versa.

The below graphs are automatically updated hourly and are based on water level recordings every 15 minutes since May of 2016. Units are in meters in reference to the mean water level at each location.
Capture


The San Juan Bay is a deepwater port with a large inlet that allows for complete tidal connectivity. There is very little influence from precipitation.



The mouth of the Puerto Nuevo River includes some tidal interference, which subdues the secondary high tide in respect to the bay.



The dredged portion of the Caño Martín Peña is almost identical to the bay, although there is slightly more response to precipitation.



The undredged portion of the Caño Martín Peña loses on average 50% of the daily tidal amplitude seen in the bay, likely due to constriction throughout the canal. It is also the most responsive location to precipitation. Water levels in the canal will rise 8 times cumulative rainfall over a few hours (1 cm of rainfall = 8cm of water level rise in the canal)



The San Jose lagoon and the west end of the Suarez canal are also influenced by constriction. Daily tidal amplitudes are 30% less than the canal east of the Baldorioty expressway, which serves as the constriction point. Water levels in these water bodies are also highly responsive to precipitation and will increase 4 times cumulative rainfall over a few hours.



The Suarez canal east of the Baldorioty is similar to Torrecillas lagoon, but is more responsive to rainfall, likely because of water draining from the San Jose lagoon.



The Torrecillas lagoon, like the San Juan Bay,  is also nearly completely tidally connected to the ocean, with very little response to precipitation.



The Piñones lagoon is the most unique water body in the estuary. It has negligible tidal connectivity, meaning its day-to-day water level fluctuations are driven almost entirely by rainfall. Note, although large changes may be perceived in the below graph, the scale of the y-axis is often much lower than the above graphs.