Colonia del Sacramento, Uruguay tide times

Colonia del Sacramento stands on a small peninsula on the northern shore of the Río de la Plata, directly across the world's widest river estuary from Buenos Aires. The historic quarter — the original Portuguese colonial settlement of Nova Colônia do Sacramento, founded 1680 — is a UNESCO World Heritage Site, its cobblestone streets and low limestone buildings preserved largely intact within their original fortification walls. The lighthouse at the point, built on the ruins of a 17th-century convent, and the ruins of the San Francisco convent alongside it are the oldest continuously maintained colonial structures in Uruguay.

The tidal regime here is unlike any other location in this dataset. The Río de la Plata is a true tidal estuary — semidiurnal tidal forcing from the South Atlantic propagates 290 km upstream to Colonia — but the river's discharge volume (primarily from the Paraná and Uruguay rivers, combined with the Iguazú) means that the water at Colonia is essentially fresh to very slightly brackish, not marine. Mean tidal range is approximately 0.8 to 1.0 m, but the actual water level at Colonia is dominated by wind setup rather than the astronomical tide for much of the year. A strong southerly or southeasterly wind (Sudestada) pushes the estuary water northward against the Uruguayan shore, raising water levels by 1.0 to 2.0 m above the predicted tidal level. Conversely, a sustained northerly wind (Pampero) draws water south and can lower Colonia's water level 0.5 to 0.8 m below the predicted low.

The wind-dominant water-level regime has practical consequences. The ferry to Buenos Aires — operated by Colonia Express and Buquebús from the main pier — crosses 50 km of open estuary in 60 to 75 minutes. The ferry schedule is fixed; sea conditions during Sudestada or Pampero events determine whether sailings proceed, suspend, or operate with restrictions. The tide prediction on this page gives the baseline water level at the pier, but the actual water level during operations depends on wind setup. The ferry companies monitor real-time conditions and adjust.

For visitors to the historic quarter, the tidal context is largely aesthetic rather than operational: the cobblestone streets running to the water's edge, the fortification walls on the estuary shore, and the view across the brown water toward Buenos Aires are the experience. The brown colour is sediment from the Paraná delta, carried into the estuary year-round. Visibility in the estuary water is essentially zero; swimming and water sports are not practised from Colonia's shore.

Fishing from Colonia is the primary water-based activity beyond the ferry crossing. Dorado (Salminus brasiliensis) — a large, powerful freshwater/estuarine gamefish — are taken in the Colonia area of the Río de la Plata by trolling from boats on the incoming tide, when the tidal push carries marine-influenced baitfish into the estuary. The incoming tide phase (from the predicted low through the mid-flood) is the productive dorado window. Surubí (Pseudoplatystoma coruscans), the large spotted catfish of the Paraná basin, are also present in the deeper channels. Local fishing guides out of Colonia run 4 to 6-hour morning trips; advance booking required.

The historic quarter demands its own time: the Calle de los Suspiros (Street of Sighs) cobblestoned from the lighthouse to the Puerta de la Ciudadela, the single room of the museum of Portuguese colonial history, the baroque church façade. The afternoon light from the west, falling across the Plata toward the Argentine shore, illuminates the fortification walls and the lighthouse in the 90 minutes before sunset — the standard photography window. The lighthouse is open for visitors and the view from the top across the estuary and the colonial roof-scape is the reference image.

Predictions on this page come from Open-Meteo Marine, a global gridded ocean model. Accuracy is ±45 minutes on timing and ±0.2 to 0.3 metres on height. The SOHMA (Uruguayan Navy) and the Argentine Servicio de Hidrografía Naval publish the tidal tables covering the Río de la Plata, with wind-correction guidance for estuary water levels.