SALINITY IMPACTS AND ROADS - NOW AND THE FUTURE

This paper attempts to identify the impact of dryland salinity on the performance and longevity of the road asset, and highlights a need for increased awareness among road managers about the extent of dryland salinity and the potential for accelerated impacts in the future. Throughout many areas of Australia it will not be possible to reverse the rising trend in the water table and reduce salinity. In most cases, living with and adapting to salinity will be the only feasible strategy for road agencies. Some insight into how high water tables and salinity are presently affecting road assets in Australia is presented along with an explanation of the apparent mechanisms associated with groundwater entering road formations. Examples of the types of damage being observed in affected regions are provided in this paper. These impacts may require changes to the way roads are designed, constructed and maintained, to ensure an acceptable service life is achieved. This will mean overall cost increases in the management of road assets in some regions. The National Land and Water Resources Audit (undertaken in 2000) provides an indication of the extent of road infrastructure potentially at risk from dryland salinity in each State. The States with pronounced and existing salinity problems include WA, Victoria, NSW and SA, while groundwater modeling is predicting a rapidly emerging problem in Queensland. Around 70% of the total road lengths at immediate risk, in the year 2000, reside in WA and a further 20% in Victoria, 5% in NSW and 5% in SA. Projections to the year 2050 indicate that the total length of roads affected will increase by a factor of more than 3 times. Annual salinity damage cost estimates for "high risk" roads only, range between $50-$100 million in year 2000, increasing to $158-$380 million by the year 2050. The CSIRO.s Division of Atmospheric Research has recently summarized the outputs from its climate change modeling program. The results predict that by 2050. 2070, winter/spring rainfall could be reduced by up to 30% in most arable parts of southern and eastern Australia. Yet, at the same time, hydro-geologists are forecasting a continuation of steady rises in water tables in this region. These kinds of changes in precipitation and evapo-transpiration are likely to lead to reduced recharge to ground waters and over time, a reduction in the area affected by high water tables and salinity. Winter/spring rainfall is a key variable affecting groundwater behavior. Monitoring in Western Victoria over the past decade shows that the water table is responding to the below average rainfall conditions. So are the climate change modelers talking with the groundwater modelers? The uncertainty in climate change science coupled with a relatively short monitoring period of shallow water tables in agricultural regions make it a challenging proposition to make changes to road asset m management strategies in light of these kinds of considerations.

Language

  • English

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Filing Info

  • Accession Number: 00964438
  • Record Type: Publication
  • ISBN: 087659229X
  • Files: TRIS, ATRI
  • Created Date: Oct 24 2003 12:00AM