Bear Lake Methods: Sed Traps

Sediment Traps

The mud that ends up at the bottom of a lake usually falls through the water first. Sediment traps collect the solid material that rains out of the water over a period of time. Using a small boat, the traps are suspended at known depths in an array (See Illustration of Sediment Trap Array).

Buoy marking the sediment trap location in Bear Lake is pulled aboard

Roger Anderson (left) of the U. of New Mexico and Allen Harrison of the Bear Lake Regional Commission haul aboard the buoy marking the sediment trap location in Bear Lake.

Retrieval of sediment traps

From left to right: Katrina Mosier of the U. of Utah, Roger Anderson of the U. of New Mexico and Allen Harrison of the Bear Lake Regional Commission retrieve sediment traps in summer 1999. For one year, the traps collected algae, zooplankton, fecal pellets and chemical precipitates (like calcite) that settled out at water depths of 9m (30ft) for the shallow trap and about 38m (125ft) for the deeper one.

The Bear Lake sediment trap automatically drops white Teflon marker beads into the collecting tube every 30 days, so that the tube ends up holding a sequence of layers made of sediment and white beads. (See the Diagram of Sediment Trap and Photo of Sediment Trap Mouth below. Also see Photos from a Sed Trap at Bear Lake).

Diagram of Sediment Trap

Diagram of Sediment Trap

Sediment Trap Mouth

Mouth of sediment trap showing the honeycomb baffles that direct particles into a plastic accumulation tube.

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