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High efficiency sediment basins

High efficiency sediment basins

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Other name/s

HES basin


A High efficiency sediment (HES) basin is a structure designed to capture sediment entrained in runoff (known as tailwater) or stormwater runoff by adding clarifying agents (coagulants and flocculants) to increase the settlement of suspended sediments.

Fine colloidal clay particles washed from intensive agricultural areas by excess irrigation water and stormwater runoff can also carry a significant load of environmental pollutants (nutrients and pesticides) to receiving aquatic environments. Clay particles stay in suspension for long periods unless chemically modified by a clarifying agent to promote flocculation and settlement.

The HES basins use automated (rain or flow activated) dosing to promote sedimentation of colloidal clay particles. The basin design promotes slow flow conditions to prevent re-suspension of settled particles. The basins can be drained (water recycled back on to productive cropping land) and the accumulated sediments dried and returned to productive land as a soil ameliorant. (Subject to ensuring that the aluminium content of the material and other factors are acceptable for agricultural use).

HES basins are generally used in areas where there are fine suspended sediments and colloidal clays with attached nutrients and pesticides.

The dosing system can be efficiently retrofitted to existing sediment basins or other artificial waterbodies.

If designed and operated correctly HES basins can have significant water quality benefits by ensuring that both coarse and fine sediments are removed from tailwater or stormwater runoff, and any associated nutrients and pesticides captured, before the water enters natural waterways. There is a risk of overdosing with the clarifying agent and this must managed with appropriate control, such as batch testing to determine the appropriate dosage.

The main services include:

  • Water treatment (Sediment, nutrient and pesticides)

Large HES basin with automated coagulant dispenser.  Photo by O2 Group
Small HES basin with ‘Floc Box’ coagulant dispenser. Photo by O2 Group


In addition to the standard disclaimer located at the bottom of the page, please note the content presented is based on published knowledge of treatment systems. Many of the treatment systems described have not been trialled in different regions or land uses in Queensland. The information will be updated as new trials are conducted and monitored. If you have any additional information on treatment systems or suggestions for additional technologies please contact us using the feedback link at the bottom of this page.

Last updated: 5 October 2018

This page should be cited as:

Department of Environment and Science, Queensland (2018) High efficiency sediment basins, WetlandInfo website, accessed 13 May 2021. Available at:

Queensland Government
WetlandInfo   —   Department of Environment and Science