The Sepik River is 1126km long and is navigable for almost its entire length. It starts up in the central mountains, close to the source of PNG’s other major river, the Fly, which flows south. The Sepik flows in a loop, first west across the West Papua border, then north, before returning east across the border. It then runs through two PNG provinces – Sandaun (West Sepik) and East Sepik.
At its exit from West Papua, the Sepik is only 85m above sea level and from there it winds gradually down to the sea – a huge, brown, coiling serpent. It has often changed its course, leaving dead-ends, lagoons, oxbow lakes or huge swampy expanses that turn into lakes or dry up to become grasslands in the dry season.
As an indication of its age and changing course, there are no stones or rocks within 50km of the river’s banks. Villages have ‘sacred stones’ that have been carried in from far away and placed in front of village haus tambarans.
The inexorable force of the river tears great chunks of mud and vegetation out of the riverbanks and these drift downstream as floating islands. There is no delta and the river stains the sea brown for 50km or more from the shore.
For much of its length, the Sepik is bordered by huge expanses of swamp or pitpit (wild sugar cane). There are hills further inland and eventually the Sepik climbs into wild mountain country near its source. Between the river and the coastal plain, the Bewani and Torricelli mountains rise to over 1000m. There are no natural harbours on the Sepik region’s 450km of coastline.
June to October is the driest time in most of the Sepik, but microclimates vary significantly. Average annual rainfalls lie between 2000mm around Wewak and Maprik, and a stunning 5200mm at Amboin. You can expect drenching rain at any time on the river, but the wet season is from December to April.
Most rain falls in January and February and the river level starts to drop after April. Temperatures and humidity can be high, but it’s usually pleasant on the river, where you catch the breeze.
Early in the dry season is the best time to visit – the mosquitoes are less numerous and there’s plenty of water in the river system. By August the level drops significantly emptying some tributaries and barets (artificial channels cut as shortcuts across loops in the river), and this makes travel times much longer.
In the dry season the Chambri Lakes can get very smelly – they shrink, fish die and weed rots.