The Mahakam River (Indonesian: Sungai Mahakam) is third longest and volume discharge river in Borneo after Kapuas River and Barito River, it is located in Kalimantan, Indonesia. It flows from the district of Long Apari in the highlands of Borneo, to its mouth at the Makassar Strait. The city of Samarinda, the provincial capital of East Kalimantan, lies along from the river mouth. The delta Mahakam river consist of specific micro climate which is influenced by high and low tide at sea level. Summary The Mahakam River is the largest river in East Kalimantan, Indonesia, with a catchment area of approximately 77,100 km2. The catchment lies between 2˚N to 1˚S latitude and 113˚E to 118˚E longitude. The river originates in Cemaru from where it flows south-eastwards, meeting the River Kedang Pahu at the city of Muara Pahu. From there, the river flows eastward through the Mahakam lakes region, which is a flat tropical lowland area surrounded by peat land. Thirty shallow lakes are situated in this area, which are connected to the Mahakam through small channels . Downstream of the connection with the Semayang and Melintang lakes, the Mahakam meets three other main tributaries – the rivers Belayan, Kedang Kepala, and Kedang Rantau – and flows south-eastwards through the Mahakam delta distributaries, to the Makassar Strait. Geology Kalimantan, where the Mahakam lies, is part of the Sunda Continental Plate. The large island has mountain ranges between Indonesia and Malaysia. As described by van Bemmelen (1949), River Mahakam rises in Cemaru () in the center of Kalimantan, from there it cuts through the pre-tertiary axis of the island east of the Batuayan () and then reaches the tertiary basin of Kutai. Its middle course traverses a lowland plain with many marshy lakes. This intermontane depression is separated from the neighboring basin, the Barito depression, by a broad hilly tract of less than altitude. After this region, the Mahakam cuts through the Samarinda anticlinorium and reaches its alluvial delta, which spreads like a broad fan over the shelf-sea, with a base of and a radius of about . Upstream of Long Iram (upstream part of Mahakam river basin) the river is flowing in tertiary rocks (Voss, 1983). Between Long Iram and Muara Kaman (middle Mahakam area) the river is flowing in quaternary alluvium, while in the downstream area between Muara Kaman and the coast including the Mahakam delta, tertiary rocks are again