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30d. Investigation into the Cause of Iron Related Clogging of Groundwater Bores Used fo Viticulture in the Limestone Coast of South Australia

Investigation into the Cause of Iron-Related Clogging of Groundwater Bores Used for Viticulture in the Limestone Coast, South Australia

Birte Moser 1,2, Meruyert Beknazarova 1 , Harriet Whiley 1 , Thilini Piushani Keerthirathne 1,
Nikki Harrington 3, Kerry DeGaris 4 and IlkaWallis 1,5,*

Citation: Moser, B.; Beknazarova, M.;
Whiley, H.; Keerthirathne, T.P.;
Harrington, N.; DeGaris, K.;Wallis, I.
Investigation into the Cause of
Iron-Related Clogging of
Groundwater Bores Used for
Viticulture in the Limestone Coast,
South Australia. Water 2021, 13, 683.

Academic Editor:
Juan Antonio Rodríguez Díaz
Received: 19 January 2021
Accepted: 23 February 2021
Published: 3 March 2021
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Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
1 College of Science and Engineering, Flinders University, Sturt Road, Bedford Park,
Adelaide, SA 5042, Australia; birte.elisabeth.moser@uni-oldenburg.de (B.M.);
meruyert.cooper@flinders.edu.au (M.B.); harriet.whiley@flinders.edu.au (H.W.);
Thilini.Ke@flinders.edu.au (T.P.K.)
2 Carl von Ossietzky University of Oldenburg, Ammerländer Heerstraße 114-118, 26129 Oldenburg, Germany
3 Innovative Groundwater Solutions, Unit 2/162 Hindmarsh Road, Victor Harbor,
Adelaide, SA 5211, Australia; nikki@innovativegroundwater.com.au
4 Limestone Coast Grape and Wine Council, Coonawarra, SA 5263, Australia; Kerry.degaris@bigpond.com
5 National Centre for Groundwater Research and Training, Flinders University, Sturt Road, Bedford Park,
Adelaide, SA 5042, Australia
* Correspondence: ilka.wallis@flinders.edu.au; Tel.: +61-08-8201-15077

Abstract: Iron-related clogging of boreholes, pumps and dripper lines is a significant and costly
problem for irrigators worldwide. The primary cause of iron-related clogging is still debated.
Previous studies have described complex interactions between biological clogging and inorganic
iron/manganese oxide precipitation. This case study examined groundwater bores used for viticulture
irrigation in the Limestone Coast region, a highly productive wine growing area in the SE of
South Australia. Iron clogging of bore screens, pumps and dripper systems has been a persistent problem
in the region and the issue is perceived to be growing, with irrigators suggesting the widespread
introduction of iron-related bacteria (IRB) through drilling equipment to be the root cause of the
problem. Analysis of the groundwater microbiology and inorganic chemistry found no apparent
correlation between the presence of IRB and the clogging status of wells. In fact, IRB proved to be
widespread throughout the limestone aquifer. However, a clear correlation could be found between
clogging affected bores and the redox potential of the groundwater with the most severely affected
bores strongly oversaturated in respect to iron oxide minerals. Elevated dissolved concentrations of
Fe(II) thereby tended to be found in deeper bores, which also were generally more recently drilled.
Following decades of less than average rainfall, a tendency to deepen bores in response to widespread
declines in water levels has been documented for the SE of South Australia. The gradually widening
clogging problem in the region is postulated to be related to the changes in climate in the region,
with irrigators increasingly driven to rely on deeper, anoxic iron-rich groundwater resources.