Much of the river valley was once fertile rainforest, but most has now been destroyed for logging and oil palm plantations.
Geography
The river flows in the northern area of Sumatra with a predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification).[3] The annual average temperature in the area is 25 °C. The warmest month is August, when the average temperature is around 26 °C, and the coldest is December, at 24 °C.[4] The average annual rainfall is 2862 mm. The wettest month is October, with an average of 446 mm of rainfall, and the driest is June, with 129 mm of rainfall.[5]