Improved salinity management for the Nebine / Mungallala / Wallam catchment

Abstract

The low stream salinity naturally in the Nebine-Mungallala Catchment, extent of vegetation
retention, relatively low rainfall and high evaporation indicates that there is a relatively low
risk of rising shallow groundwater tables in the catchment. Scalding caused by wind and
water erosion exposing highly saline sub-soils is a more important regional issue, such as in
the Homeboin area. Local salinisation associated with evaporation of bore water from free
flowing bore drains and bores is also an important land degradation issue particularly in the
lower Nebine, Wallam and Mungallala Creeks. The replacement of free flowing artesian
bores and bore drains with capped bores and piped water systems under the Great Artesian
Basin bore rehabilitation program is addressing local salinisation and scalding in the vicinity
of bore drains and preventing the discharge of saline bore water to streams.
Three principles for the prevention and control of salinity in the Nebine Mungallala catchment
have been identified in this review:
• Avoid salinity through avoiding scalds – i.e. not exposing the near-surface salt in
landscape through land degradation;
• Riparian zone management: Scalding often occurs within 200m or so of watering lines.
Natural drainage lines are most likely to be overstocked, and thus have potential for
scalding. Scalding begins when vegetation is removed, and without that binding cover,
wind and water erosion exposes the subsoil; and
• Monitoring of exposed or grazed soil areas.
Based on the findings of the study, we make the following recommendations:
1. Undertake a geotechnical study of existing maps and other data to help identify and target
areas most at risk of rising water tables causing salinity. Selected monitoring should then
be established using piezometers as an early warning system.
2. SW NRM should financially support scald reclamation activity through its various
funding programs. However, for this to have any validity in the overall management of
salinity risk, it is critical that such funding require the landholder to undertake a salinity
hazard/risk assessment of his/her holding.
3. A staged approach to funding may be appropriate. In the first instance, it would be
reasonable to commence funding some pilot scald reclamation work with a view to further
developing and piloting the farm hazard/risk assessment tools, and exploring how
subsequent grazing management strategies could be incorporated within other extension
and management activities. Once the details of the necessary farm level activities have
been more clearly defined, and following the outcomes of the geotechnical review
recommended above, a more comprehensive funding package could be rolled out to
priority areas.
4. We recommend that best-practice grazing management training currently on offer should
be enhanced with information about salinity risk in scald-prone areas, and ways of
minimising the likelihood of scald formation.
5. We recommend that course material be developed for local students in Years 6 and 7, and
that arrangements be made with local schools to present this information. Given the
constraints of existing syllabi, we envisage that negotiations may have to be undertaken
with the Department of Education in order for this material to be permitted to be used.
We have contact with key people who could help in this if required.

6. We recommend that SW NRM continue to support existing extension activities such as
Grazing Land Management and the Monitoring Made Easy tools. These aids should be
able to be easily expanding to incorporate techniques for monitoring, addressing and
preventing salinity and scalding. At the time of writing staff of SW NRM were actively
involved in this process. It is important that these activities are adequately resourced to
facilitate the uptake by landholders of the perception that salinity is an issue that needs to
be addressed as part of everyday management.
7. We recommend that SW NRM consider investing in the development and deployment of
a scenario-modelling learning support tool as part of the awareness raising and education
activities. Secondary salinity is a dynamic process that results from ongoing human
activity which mobilises and/or exposes salt occurring naturally in the landscape. Time
scales can be short to very long, and the benefits of management actions can similarly
have immediate or very long time frames. One way to help explain the dynamics of these
processes is through scenario modelling.