Description: The stilling well is a surface water level infrastructure that is commonly used with a shaft encoder to protect the float and stable the water fluctuation caused by turbulence and wind. Stilling wells are typically installed along the bank of a stream, canal or along the pier of a bridge. Inlet pipes are located at various levels (typically 0.3m vertical increments) and should be placed at level right angles to the direction of flow. Having multiple inlet pipes at incremental vertical levels allow for continuous operation if silt covers lower inlets during high water events. Inlet pipes and the well itself is subject to sedimentation, resulting in blocking of the inlet pipes and filling the bottom of the stilling well. Routine maintenance requires occasional flushing to remove sediment. To minimize significant delay in the rise and fall of stage, inlet pipes should be of considerable number and size. The most common inlet pipe size used is 0.05m, but in some places up to 0.1m diameter pipe is used.
Stilling wells should be installed to cover the full range of water level. It should be below the anticipated minimum stage and above the level of 200-year flood. The cost of installation for the stilling well is among the most expensive for water level sensor infrastructure
Costs USD Lower: $5,000
Costs USD Upper: $30,000
Accessories: shaft encoder, float, tape, wheel, shaft, staff gauge
Advantages: Stilling wells are generally used to mount a shaft encoder with float/counterweight. There have been instances where submersible transducers or bubbler systems have used the stilling well system. Stilling wells are extremely helpful at removing fluctuations in water level that occur over a short time period (seconds)
Disadvantages: Stilling well systems allow sediments to enter the stilling well. Once in the stilling well, the sediments settle, and if not regularly cleaned, can significantly impact water level measurement.
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