Sepik

Observatory History

The Sepik River Observatory is our newest observatory: Although we have a few older samples from 2001 and 2017, monthly sampling started in May 2019.  Logistics are complicated, and without the help of our observatory manager Lucas Kou we could not sustain the observatory.

The Sepik River is one of the few larger and still free-flowing tropical river systems in the World.  It has, luckily, also escaped some of the deleterious impacts humans have on the environment.  Its sister basin to the south, the Fly River basin, is now heavily contaminated from mining activities in the Papuan Highlands (Ok Tedi Mine).  The threat of potential disturbances, such as the planned Frieda Mine on the mountainous Frieda River tributary of the Sepik River, is real, and it is high time to better understand the biogeochemistry of the Sepik River while it is still much more pristine than the Fly River.  Ongoing deforestation, particularly near the border to Irian Jaya, is another concern.  Below are a few measures of this fascinating watershed.

Watershed statistics

  • Country: Papua New Guinea, Irian Jaya (Indonesia)
  • Large-scale drainage area: East Asia (Pacific)
  • Drainage: 101,821 km2 (other sources cite a smaller drainage area of ~79,000 km2)
  • Runoff: 120 km3/year
  • Suspended sediment: 44 Mt/yr
  • Population density: 9 people/km2
  • Large cities: 0
  • Forest: 77%
  • Grassland: 14%
  • Cropland: 7%
  • Developed: <1%
  • Deforestation rate: 3%
  • Forest loss: 24%
  • Large dams: 0
  • Sediment trapping efficiency: x (fraction)

Reference: Revenga, C., S. Murray, J. Abramovitz, and A. Hammond, 1998. Watersheds of the World: Ecological Value and Vulnerability. Washington, DC: World Resources Institute.