Description
This completely new approach to water management is based on the tonnage of salt imported rather than on the Mega Litres of water. Completed in 2005, the Clare Water Supply Scheme in South Australia was built to distribute additional water from the Murray River through the Clare River and beyond.
So that the imported water can be used for irrigation without increasing the salinity of the soils or groundwater in the Clare district, a framework has been developed to enable irrigators to identify and to manage the environmental risks associated with the use of River Murray water for irrigation.
The adopted framework has five innovative components.
First, to limit and control salt accumulation over decades, irrigation water is allocated on the basis of its salt load rather than by volume.
Second, the irrigation water can be applied only in a sub-catchment where the groundwater salinity trend is decreasing; it cannot be applied where the groundwater salinity trend is stable or increasing.
Third, irrigators use district-scale Risk Maps and they undertake property-scale soil surveys to avoid applying irrigation water (and salt) onto areas where salt will accumulate.Soils data and the Risk Maps have been provided to irrigators as geographic information system map layers on an interactive computer compact disc.
Fourth, equivalent salt loads are calculated to enable the exchange of a license to access existing water resources (i.e. groundwater and / or surface water) for a license to access a larger volume of lower salinity, River Murray (pipeline) water.
Finally, monitoring and Irrigation Annual Reporting have been added to the conditions on water licenses.
Lessons learned
- The water licensing policies determine the locations at which salt will accumulate and the number of years that will pass before salt becomes the major issue.
- A single source of regular, clear, consistent communication is essential to avoid confusion and to win support for any innovative strategy.
- History shows that salt accumulation has caused the eventual failure of most irrigation schemes.
- A salt management strategy is highly relevant wherever there are plans to irrigate land that has not previously been irrigated.
Importance of the case for IWRM
- Assessing the capability of land to be irrigated without being damaged
- Applying irrigation only onto appropriate land
- Monitoring and reporting on the how the land and the height of the water table are affected after irrigation water is applied
Photo credit: Stefan Krasowski