The major rivers of Puerto Rico are the La Plata River, the Río Grande de Loíza, the Bayamón River and the Río Grande de Arecibo. All the major rivers of Puerto Rico flow northward over the mountains to the Atlantic Ocean.
The La Plata River is the longest of the rivers, located on the northern part of the island. It is approximately 60 miles long. The Río Grande de Loíza is the widest and the second longest on the island, running for 40 miles. The Rio Bayamón River runs through the municipality of Bayamon, which is located on the northern coastal valley. The Río Grande de Arecibo also flows through the northern part of the island, passing along a gorge that is 200 meters deep and 800 to 1,200 meters wide.
There are fewer rivers in the southern part of the island, and they are generally shorter and lesser in volume than the ones in the north. Many of the rivers running south run dry for the majority of the year. Puerto Rico does not have any sizable, natural, perennial lakes, although it does have 15 reservoirs which are referred to as lakes. These reservoirs are formed by the damming of the main rivers.