How to prevent dirty water from getting into your dam.
Silt trap or sediment trap is a structure that is constructed up a river channel for the purposes of controlling soil, sediments, metals or any unwanted object into a reservoir dam. Silt traps prevent dams from getting filled up quickly, especially when relying on run off water. The trap also ensures that water that enters the dam is clean and will not destroy irrigation systems when used. It also acts as a spill way, channeling excess water away from the dam reservoir when full.
Components of a silt trap
A silt trap needs to be installed just before a dam. In most cases, they are installed a few meters to the reservoir when all the dirt has been carried.
- Inlet channel. This is the section that carries water into the dam.
- The sediment trap (That actually traps the dirt)
- Spill way channel-That drains excess water once the reservoir is full.
- Mitre drain. This drains water from the shoulders of the dam to the trap
Construction of the silt trap
A silt trap is constructed using sand, ballast and cement with bricks. It is composed of two chambers each measuring 70cm x 50cm x 60cm or 60cm x 60cm x 60cm (L,W,H). For large reservoirs, the size of the sediment trap has to be increased to accommodate huge amounts of run off water.
The inlet to the dam is made of 3 holes each fitted with pvc pipes from 2’’ to 4’’ depending on the dam size.
During construction, the conveyance channel may be constructed in a zig zag manner to reduce the speed of water. Make a point of planting grass along the water way to assist in filtering dirt and debris. You can also carry out stone pitching or pegs of tree branches to enable sedimentation ahead of the entry chamber.