The strait is about wide from the east coast of
Belitung (also known as Billiton) to the west coast of Borneo (Kalimantan). The much narrower
Gaspar Strait separates Belitung from
Bangka Island to the west. Bangka lies close to the east coast of Sumatra, separated from it by the
Bangka Strait. To the east of Belitung lie reefs and a group of islets known as the Montaran Islands, extending up to from Belitung's northeastern coast. The
Karimata Islands lie in the eastern part of the Karimata Strait, northeast of Belitung, southwest of Maja Island, and off-shore from the west coast of Borneo. The presence of these islands and reefs reduce the width of the main navigable channel to about . Outside this main fairway, there are multiple navigable channels to the east of Karimata Islands or between the islands. The Rivers
Kapuas, Kendawangan,
Pawan, and
Sambas (in Borneo), as well as the Rivers
Barumun and
Musi (in Sumatra) empty to the strait.
Climate The southeast
monsoon prevails in the strait from about the end of May, which comes with strong southeast or south-southeast wind, a dry weather, and mist that can obscure visibility. The northwest monsoon comes from the beginning of October, characterized by thunderstorms, rain and squalls alternating with calm days with fair weather. The biggest rainfall occur from November to February. From February, the weather becomes unpredictable because of the changing monsoon, before settling again around the end of May.
Currents and water transport The current strength of the strait vary depending on the monsoon wind. At the peak of either monsoon, the current can run up to When the monsoon is light, "there is little or no current" and the direction may be subject to the
tidal stream. The strait's currents run between the
South China Sea to its north and the
Java Sea to its south. Since it is relatively shallow, with the depth of or less, the volume transported by the current is relatively small. A 2007–2008 study by a group of Indonesian and Chinese researchers found that the transport volume averaged 500,000 m3/second (or 0.5
Sv) with a net southward direction (i.e. to the Java Sea). During the northern hemisphere winter, roughly during the northwest monsoon, water flowed southward averaging 2.7 Sv. The flow was reversed during the northern hemisphere summer, roughly during the southwest monsoon, with an average transport of 1.2 Sv. == History ==