up to , and forming a single volume of water with them. This outflow prevents massive flooding of the lower reaches of the river; it also promotes fish migration from the river to the lakes for spawning, but drives birds away from the lakes. The river discharges into the South China Sea creating a marshy delta, which spreads both inland and into the sea, with the silt deposits extending up to from the Borneo coast. The delta is located west-southwest of Pontianak, the capital of West Kalimantan province, which lies at the equator. The delta has five arms, of which the northernmost one is the widest, and is therefore called the Big Kapuas (). The largest tributary is the Melawi River, which occurs to the left near the city of Sintang, about 465 km from the mouth. Other major tributaries are the Landak, Kubu, Punggur and Sekayam rivers. Climate The climate is warm and very humid, with the average annual precipitation ranging from year to year between , and the number of rainy days between 120 and 309; the largest precipitation was observed in 1976 (120 rainy days) and the wettest in 1988, with only 184 rainy days. The temperature is rather stable with a typical minimum of and maximum of through the whole year. Flora and fauna In the upper and middle reaches, the river flows through dense tropical forests; the rich flora and fauna are the subject of international research. Discoveries of new species are frequent, such as of the Kapuas mud snake (Enhydris gyii), which was discovered in 2003–2005 by German and American herpetologists. This species is remarkable in that it can spontaneously change its skin color, similar to the chameleon. Otters and crocodiles are common in the Kapuas River, but frogs are nearly absent. Agile gibbons (Hylobates agilis), Müller's Bornean gibbons (Hylobates muelleri), Prevost's squirrels (Callosciurus prevostii) and treeshrews inhabit the trees above the river. There are two national parks on the river banks, Betung Kerihun with an area of 8,000 km2 and Danau Sentarum (area 1,320 km2), the latter includes the Kapuas Lakes. Fish About 300 species of fish have been identified in the river basin, of which 234 are of high economical value. This is more fish species than any other river basin in Indonesia. They belong to 120 genera and 40 families with the two major groups being cyprinids and catfish. More than