overview of possible impacts from coal seam gas
development in Northern Rivers, New South Wales
Project by Elfian Schieren, 2012
4. Risks to water resources from coal
seam gas development
4.1 Groundwater use
Impacts of overexploitation and
contamination of water are particularly concerning to residents in CSG
Most of the CSG development in QLD and NSW
overlies the Great Artesian Basin where a huge expansion of CSG exploration and
commercial CSG production has occurred in the Surat Basin (Queensland Water
Processes used to remove methane from coal
seam, such as dewatering, involve the exchange of large volumes of water from a
higher to a lower grade of produced water (Queensland Water Commission, 2012).
The process of dewatering creates a vacuum
into which water from overlying or adjacent aquifers will tend to flow and can
potentially remove large amounts of water from subterranean aquifers quicker
than recharge can occur (Winders, 2012).
This can create cones of depression in the
water table causing drawdown in existing bores which is particularly concerning
for bore water users as it has the potential to impacts rural domestic water
supplies (Winders, 2012).
Density of CSG wells could be a potential
factor in groundwater impacts. Petroleum extraction well clusters have been
shown to cause detrimental impacts to groundwater levels in the Eastern
Province, Saudi Arabia (Abderrahman et al., 1995).
Produced water can be considered a
reduction in water due to the fact that it involves contaminating higher quality
water with salts and other drilling or fraccing compounds or compounds naturally
occurring in the coal seam.
This creates a potential loss of
opportunities to use the water for potable and other domestic purposes (NTN,
Modelled predictions on the long term
impacts of CSG water production in the Walloon Coal Measures suggest up to 150m
depressurisation which would cause a maximum drawdown of 21m within existing
bores (Queensland Water Commission, 2012).
Declining ground water levels are expected
to start impacting the Condamine Alluvial, a major water resource in Western
Downs, QLD, by 2017 and estimate a net loss of 1,100M/L per year over the next
century (Queensland Water Commission, 2012).
Several farmers in Western Downs have
already experienced drawdown in their bores.
Mining companies promise to “make good” any
inconveniences to the landowner but the economic viability of making good is
A hydro-engineer and feedlot owner from
Western Downs estimates that water loss to a bore supplying 200 head of cattle
would cost $216 per day, equal to $78 840 per year (Winders, 2012).
There are currently 21,000 bore users at
risk of drawdown impacts suggesting there is a considerable cost involved for
gas companies “making good” if even only half of these people demand
compensation (Queensland Water Commission, 2012).
It is estimated that only 528 of registered
bore users will experience such water loss as to trigger make good agreements
but this figure is based on modelling (Queensland Water Commission, 2012) and
may not be totally accurate.
According to Australia Pacific LNG, Origin
and Conoco Phillips (2012) there will be an estimated 75,000ML – 140, 000ML/year
removed from the Great Artesian Basin (GAB) through CSG production.
Their estimates state that the GAB is
recharged by 912,120ML/year and therefore will not suffer significant impacts
from CSG (Australia Pacific LNG, 2012).
According other estimates by SMICCSG
(2011), based on current production schedules CSG, water production is expected
to peak around 200, 000ML/year in the Surat Basin alone.
The difference in these figures illustrates
the uncertainties of CSG water impact assessments.
Proper scientific assessment of water
impacts is restricted by the fact that much of the existing data is held by coal
seam gas companies in industry confidence (NSW Parliament, 2012).
Generally, impacts are considered by most
studies to be variable and dependent on geology and level of CSG development (SMICCSG,
Most likely the more serious drawdown
impacts will be regional and localised (Abderrahman et al., 1995).
Globally, water scarcity in the face of
population increase and climate change is considered a far greater threat to the
global community than climate change itself and recommended as a priority
management for all nations (Vorosmarty et al., 2008).
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