The Siak (Sungai Siak) is a river of Riau province, in the east of Sumatra, Indonesia, about 1000 km northwest of the capital Jakarta.[2] Approximately 370 kilometres in length, the Siak is a blackwater river which owes its brown color to dissolved organic matter (DOM) leached from surrounding, heavily disturbed peat soils; it is heavily polluted, notably by the petroleum industry. It flows through the town of Pekanbaru before emptying into the Strait of Malacca.[3]
| Siak
Sungai Siak, Siak rivier
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|---|---|
The Siak River as it flows through Pekanbaru
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  Location of river mouth  Siak River (Indonesia) Show map of Indonesia | |
| Location | |
| Country | Indonesia |
| Province | Riau |
| Physical characteristics | |
| Source | |
| • elevation | 0 m (0 ft) |
| Mouth | Malacca Strait |
| Length | 370 km (230 mi) |
| Basin size | 10,423 km2 (4,024 sq mi)[1] |
| Discharge | |
| • location | Siak Delta, Malacca Strait |
| • average | (Period of data: 2009–2013)720 m3/s (25,000 cu ft/s)[1] |
The river flows in the central area of Sumatra with predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification).[4] The annual average temperature in the area is 23 °C. The warmest month is October, when the average temperature is around 25 °C, and the coldest is January, at 22 °C.[5] The average annual rainfall is 2673 mm. The wettest month is November, with an average of 418 mm rainfall, and the driest is January, with 106 mm rainfall.[6]
1°14′16″N 102°10′00″E / 1.23778°N 102.16667°E / 1.23778; 102.16667