State of the Environment Report 2007
Waterlogging was identified as an issue in the 1998 State of the Environment Report (Government of Western Australia, 1998), however it was not identified as a major environmental issue for this report. Other parts of this report (see 'Altered water regimes') consider broad changes to water levels in the catchment, including the effects of waterlogging.
Waterlogging represents excess amounts of water in the plant root zone of soils. It occurs naturally in low-lying wetland areas and near waterways where plants are suitably adapted for such conditions. However, problems arise when land is cleared of native vegetation and water infiltration to the soil (either from rainfall or irrigation) begins to exceed evaporation or plant water use.
Plants are particularly susceptible to the effects of waterlogging, causing damage and death to plant roots. It reduces soil oxygen levels, causing a build up of gases toxic to plants and alters the nutrient levels around roots. On agricultural land it may reduce crop and pasture productivity, and reduce the available cropping area. Excessive waterlogging may also cause pooling of water at the surface (inundation) leading to increased surface runoff, flooding, soil structure decline and erosion. Runoff may also export salt, nutrients and sediment to lower areas in the catchment.
Waterlogging and salinisation are closely related and can be managed by using or removing excess water from the soil. This may be achieved through the planting of perennial vegetation, approved drainage works, or engineering options such as groundwater pumping (see 'Land salinisation').
Areas most susceptible to waterlogging include agricultural areas along the Swan Coastal Plain, the Scott Coastal Plain (east of Augusta) and low-lying areas in Wheatbelt valleys (Figure L6.1). Although many of these areas are still susceptible, waterlogging is now perceived to be a lesser environmental problem. It is possible that reduced rainfall in the South West over the past few decades (see 'Climate change') has reduced the extent and severity of waterlogged areas. In addition, many farmers in affected areas also believe the problem can now be adequately managed.
![Figure L6.1: Risk of waterlogging inundation in the South West. [Data source: Department of Agriculture [ver. 2005]; Presentation: Department of Agriculture.]](/site/files/images/Figure-L6.1_Large.jpg)
