The drainage network
The drainage network has a range of functions:
- To remove floodwaters caused by significant annual rainfall events and mitigate the impact of broad-scale and prolonged inundation of production land and groundwater recharge - requiring surface water drainage;
- To drain saline groundwater from the upper soil profile in the ‘at risk’ parts of the landscape and thereby mitigate the effect of salinity in the root zone of pasture and native plant species – requiring deeper drainage
- To provide for appropriate environmental flows to key wetland systems of regional, national and international significance - requiring flood-ways and regulators for manipulation of fresh surface water resources.
What is a drain?
There are three major types of drains in the region.
Surface water drains
- Surface water drains aim to drain surface water from the landscape, generally without the requirement to intercept groundwater (i.e. relevant in the lower South East and parts of the upper South East).
Flood mitigation drains
- Floodwater drainage serves to alleviate the broad-scale and prolonged inundation of the landscape, associated with significant seasonal rainfall events. Such inundation has been known to put large areas modified for production under water for many months.
- Groundwater drainage provides for drawdown of saline groundwater away from the surface root zone of plants. Most significantly this drawdown of the groundwater table during the summer months can impede the wicking (drawing up) of salts into the root zone by lowering the water-table beyond the effective zone of influence of evaporation.
There are a number of elements and considerations involved in managing the drainage network. The four main areas are:
- Built Assets
- Plant and Equipment
- Drain Maintenance
- Flow Management