Behind the Seams: strategic cropping land and CSG water use
The bill to protect strategic cropping land in Queensland became operative in January. But how is the SCL legislation supposed to protect the land? asks Dr Peter Dart, an associate professor in agriculture and food sciences at the University of Queensland.
Legislation to protect strategic cropping land in Queensland became operative in January. But how is the SCL legislation supposed to protect the land?
The Queensland government has established trigger maps based on land suitability for cropping: the best land in Queensland of which there is precious little (maximum 4% of total area). These maps are based on current knowledge of the land characteristics and use.
In these SCL designated areas, if land use other than cropping such as mining or extraction of coal seam gas via wells is proposed the proponents must undertake an SCL assessment against a set of eight criteria devised by the Department of the Environment and Resource Management (DERM), which differ between the four regions -- Western Cropping, Eastern Darling Downs, Coastal Queensland and Wet Tropics.
These criteria are based on soil properties such as the amount of stones, amount of clay and water-holding capacity, depth of soil, drainage rate, microrelief, soil acidity and chemical composition and slope set at only 3% for the Western Cropping zone and 5% for the Eastern Darling Downs. Many good quality soils occur and are used productively, for example for horticulture, at greater slopes.
Some of the criteria such as slope have errors associated with the measurement depending on the instruments used and hence inaccurate measures can lead to a non-SCL classification enabling alternative. Some of the criteria require field skills to measure, some are time consuming and others require laboratory equipment now not often used.
The Australian Society for Soil Science Inc (ASSSI) Queensland branch wrote to the then minister Nolan in July 2011 about its concerns with these criteria and the way they would be measured and used. The minister, for example, can invoke an "exceptional circumstance" clause to overrule, in the public interest, an SCL determination. This could be an "overwhelmingly significant opportunity to benefit the state" economically, though no guidance is given on how this would be determined.
The minister accepted the need for further refinement of the SCL criteria and established a Science and Technical Implementation Committee with two representatives nominated by the ASSSI, one by the Queensland Farmers Federation and one from expert the Queensland Resources Council. The committee has recently met to be briefed by DERM on the rationale for the criteria.
A major linked issue around the future development of CSG extraction is the lack of soil science expertise available to undertake the SCL measures and in DERM to monitor the classifications and the operation of the CSG Companies Environmental Authority Land Management Plans, and mediate disputes. This is a national problem and state and federal governments, professional societies, universities and farmer organisations are very concerned.
There was no one graduating last year from the University of Queensland with advanced training in soil science and very few elsewhere in Australia. Something has to be done about this and soon, and it cannot be overcome by importing expertise. The CSG companies are attracting staff from DERM, with some 68 resignations since January 2010.
The other major problem with CSG mining is the management of the very large volumes of CSG associated water, estimated by the National Water Commission to be as much as 300 gigalitres per year when the CSG extraction is in full swing, amounting to 55% of that estimated to be currently taken overall from Great Artesian Basin. A major issue is the time taken to recharge this water resource with the time scale is in thousands of years for water to travel down to the aquifers.
The GAB current recharge rate is estimated at 1000 gigalitres per year. A regional assessment of the effect of CSG mining on the aquifer water balance is necessary to gauge how drastic such withdrawals of water might be on future sustainability of the Murray-Darling Basin water supplies especially as the current proposed MDB plan has factored in increased ground water extraction for farm and town use. Basically not enough is known of the hydrology of the Surat and Bowen basins to understand issues around connectivity of aquifers as the Australian National Water Commission and the Wentworth Group of Concerned Scientists has indicated.
The CSG "associated" water occurs with the gas in the coal seam and has to be extracted with the gas. The water quality varies but is generally salty, and needs to be treated before it can be used or disposed of. It cannot now just be evaporated from very large surface dams and the preference is to inject reverse osmosis treated water into shallow aquifers used by farmers or untreated water into aquifers with worse quality water that are confined and not connected to others. Another option canvassed is to substitute the CSG water for the water farmers store in surface ring tanks thereby reducing the amount of water taken from the aquifers normally to fill these tanks. This would increase the amount stored in the aquifers for future use once the CSG extraction is over.
But the logistics of piping the CSG water to these scattered storage systems are difficult.
All this takes a lot of energy whose production releases carbon dioxide. Just letting the treated water infiltrate to aquifers passively from surface ponds does not work well enough. This of course affects the life cycle analysis for CSG and its touted benefits for energy production through less greenhouse gas emissions than coal.
If the CSG water leaks from holding dams or pipes before treatment the effect on soils and Murray-Darling Basin waterways can be an environmentally disastrous outcome. Overtopping of dams or DERM allowed release to prevent the dam collapsing in floods is a linked issue and has happened several times during the floods over the past two years. Salt can really stuff up soils’ beneficial properties and governments provide guidelines on the salinity level of irrigation waters for this reason. Further the Queensland government has agreed to minimise the loading of salt into the Murray-Darling Basin.
There have been instances already where saline water has been released when pipes burst or well head systems fail. Pipe burst will be an ongoing hazard in the black cracking clay Vertosol soils of the Darling Downs. Enormous forces result when soils crack and swell often by as much as 30% and pipes will buckle under these. The major CSG companies in their environmental impact statements indicate that CSG pipes will be buried including the major pipelines to Gladstone and Curtis Island.
After the RO clean up of the water there will be millions of tonnes of salt produced and stored initially as brine in holding dams while a way to use or dispose of the salt is worked out. And we are scheduled to go from more than 7000 wells (Australian Petroleum Production and Exploration Association figure) at present to industry guestimates of 30,000-40,000 wells in Queensland by 2030.
Adaptive management is the name of the game if anything goes wrong but how this will operate to restore aquifers that have been drawn down or polluted with salt or soil that receives salty water is anybody’s guess.
The potential to pollute aquifers from CSG operations arises from connections between the sweet water, shallower aquifers used for irrigation and home and town water supplies and the Walloon coal measures aquifer, part of the Great Artesian Basin, lying usually several hundred metres below. There is some evidence that this is the case when the measures rise towards the soil surface in some locations. Further the CSG well linings of iron and concrete have to last in perpetuity to prevent leakage from the Walloon measures which will likely remain pressurised, into the overlying aquifers. Such breaches have occurred with shale gas wells in the US. There is a major issue of quality control for the steel liners reportedly imported from China and the integrity of the cement lining (remember Deepwater Horizon failure) exacerbated by the sheer number of wells being drilled.
Hopefully the five-member, newly formed interim independent expert scientific committee on coal seam gas and coal mining lobbied for by Tony Windsor, will take account of the precautionary principle in their deliberations.