Moving water @ Sydney

There was a bit of hubbub recently, when CSIRO became aware of the advertisement produced by Australian Petroleum Production & Exploration Association (APPEA) that claimed in an ad that there would be no impact on groundwater from coal seam gas mining. CSIRO immediately responded and asked for the ad to be removed. I found this interesting for two reasons.

The first reason is that the actual behaviour of APPEA exactly demonstrated what I wrote about in my last blog. Here a company is “hiding” behind CSIRO (the scientists) arguing that science has approved their actions. I put hiding in quotes, as you can think of other words to describe the action. On the other hand the scientists are feverously communicating what they actually meant and highlighting uncertainty. So what did CSIRO actually say (which leads up to my second reason)?

I had a look around the CSIRO website and found this informative page that covers coal seam gas and groundwater in a bit more detail. On one of the factsheets (Coal seam gas developments - predicting impacts), clearly highlights that predicting impacts is challenging. They highlight spatial variation in landuse, the time lag between extraction and impacts and scarcity of groundwater data. All these things have been highlighted before and mean that all predictions about coal seam gas impacts have a reasonably high uncertainty and therefore need to be treated with caution. This is probably the small letters that APPAE did not read?

My second reason for finding this interesting is in the response from CSIRO on the claims. In their press release they argue that coal seam gas extraction has a low risk of causing groundwater contamination based on their modelling. I am not questioning this, I am sure this is based on a rigorous scientific analysis using the “best available data” (Given their earlier statement about the scarcity of data this could be very little data). They clearly frame this in terms of risk (thus a probability) not as an exact figure. In other words, the science shows there is a possible impact, but its occurrence is unlikely or small.

They then go on to say that: “CSIRO has also indicated that groundwater levels will fall as a consequence of coal seam gas extraction. In some places this could see aquifer levels subside by tens of metres for tens of years; in others it is likely to reduce aquifer levels by several metres for several hundred years.” In other words there is an impact on groundwater quantity but this is localised. This is what made me interested. We can now frame risk not only in terms of occurrence but also in terms of spatial impact. Thus we can have a high impact which is highly localised and thus would still be an overall low risk (across a larger area). We then need to start thinking if a high risk but small area impact is a greater risk than a low risk large area impact. I am not sure I can solve that one yet. I think it comes down to the same principle as exposure × toxicity for chemicals. In other words, if more people are affected by a low risk large area impact then this is probably worse than a high risk small area impact.