Raise water level to restore/create brackish/saline swamps from other land uses
Overall effectiveness category No evidence found (no assessment)
Number of studies: 0
Background information and definitions
This action involves one-off action to raise the water level/table to restore/create swamps from other land uses. This means that intervention should (a) occur at one point in time, after which the water table is not actively managed, and (b) must affect an area that does not retain substantial characteristics of the target habitat. This could be an upland area (e.g. grassland), an unvegetated wetland (e.g. mudflats), or a wetland other than the target type (e.g. marsh, where the habitat used to be a swamp).
Specific techniques to raise water levels include: blocking drainage ditches (using sediment, rocks, plastic dams, wooden dams or vegetation); building raised embankments, berms or levees to retain water; switching off drainage pumps; ceasing groundwater extraction; installing or widening culverts (e.g. under roads and railways, to increase water flow into focal marsh/swamp); removing dams upstream of the focal marsh/swamp; and reprofiling or diverting river channels to raise the water level on floodplains. All of these techniques aim to make soils saturated or flooded, or make them saturated or flooded for longer, so they can support emergent wetland vegetation. The resulting water level may be stable or fluctuating, and may create permanently or seasonally flooded wetlands. Sediment inputs may also increase in line with water inputs.
Caution: This action may have negative effects on habitats elsewhere in the catchment. For example, removing dams upstream of a focal site could drain wetlands or aquatic habitats upstream of the dam. There may also be conflicts with water needs of human populations that need to be managed. Rewetting drained acid sulphate soils – common in coastal areas and salinized inland areas – can lead to acidification, deoxygenation and release of toxic metals (Baldwin 2011).
Related actions: Raise water level to restore degraded swamps; Actively manage water level; Reprofile/relandscape or Remove surface soil/sediment, both of which can lower the ground surface towards the water table; Raise water level to complement planting; Restore/create marshes or swamps using multiple interventions, often including water level manipulations.
Baldwin D. (2011) National Guidance for the Management of Acid Sulfate Soils in Inland Aquatic Ecosystems, Environment Protection and Heritage Council and the Natural Resource Management Ministerial Council, Australia.