Off-site effects from salinity? Questions to ask your hydrologists
David Pannell
University of Western Australia
I have presented a number of hydrological and economic reasons why off-site effects from salinity are not nearly as important to salinity management in Western Australia as has been widely perceived (see Pannell et al., 1999). I strongly believe that other states of Australia also need to reconsider and review the significance of off-site effects, as it has a big influence on the sorts of policies and strategies that are sensible to consider. To help with this process of re-consideration and review, I provide here some advice on the types of questions that need to be asked of hydrologists to understand the significance of off-site effects in a region. The economic arguments in Pannell et al. (1999) are also relevant, but I suspect that the hydrology is the issue that will vary most markedly between regions.
The key questions are:
The common feature about all of these questions is that they focus on the impacts of treatments. This is the necessary focus if we are to have the information needed for decision makers (both farmers and policy makers).
No doubt, in many situations, the information will not be available to answer these questions decisively. However it is important that the questions be asked even in these cases. Hydrologists need to know that these are the most important hydrological questions for decision making on farms and by policy makers.
A question of limited relevance is: If we continued with current management, what would be the eventual extent of salinity. This is a commonly addressed question but it generally provides a very poor indication of the benefits and costs of the available salinity treatments, which is what you really need to know. At best it sets an upper limit on the combined benefits, but the actual benefit of any treatment is usually very far below that upper limit. What is actually needed is a comparison of salinity impacts over time with and without particular treatments. The without treatment case is no more that half the story.
Another question that often does not help you much is: Were particular salinity problems caused or contributed to by clearing of farms at some distance away? If the answer turns out to be "no", you have some useful information about where to implement treatments, but if it is "yes", you probably don’t. Just because clearing has contributed to off-site salinity, it does not necessarily follow that revegetation at the remote site will be an effective strategy for fixing the problem. See the examples relating to towns, rivers and natural reserves in Pannell et al. (1999) for more details on this.
Be wary of answers to your questions that "such and such can happen". For example, planting trees on a farmer’s property can prevent salinity occuring on land at some considerable distance away. You want to know, in what circumstances "such and such" is likely to happen, how likely it is in those circumstances, and how common those circumstances are.
In summary, you should focus on comparisons of salinity with and without implementation of treatments, not merely on forecasts for the without treatment case. The comparison must be forward looking, not historical. The comparison should bring out differences in salinity year by year, not just in the final equilibrium level. And you should focus on the likelihood of different outcomes, not on what can happen.
Citation: Pannell, D.J. (2000). Off-site effects from salinity? Questions to ask your hydrologists, SEA Working Paper 99/11q, Agricultural and Resource Economics, The University of Western Australia. http://www.general.uwa.edu.au/u/dpannell/dpap9911q.htm
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