Lockyer Valley erosion risking Brisbane's drinking supply An eroded creek bank near Clarendon. Photo: Jose Abad Brisbane, you have a problem. And your problem is eroded topsoil. Eroded topsoil from Lockyer Valley farms is Brisbane's Achilles' heel. Darren Jahnke shows the revegetated stream bank beside his flood affected Lockyer Vally farm. It is Brisbane's Achilles' heel because it will choke our drinking water. Earlier this month, SEQ Catchments, a not-for-profit environment group trying to prevent erosion in the Lockyer Valley, took Fairfax Media for a tour to explain the extent of the problem. That followed the Healthy Waterways report card on October 23, which for the 13th year in a row showed Moreton Bay was suffering from soil washing into it from Lockyer Valley farms. Revegetation underway at Laidley Creek, behind Mulgowie Pub, in order to stop erosion. Weeks later in November, we were standing on top of a 30-metre high bank of rich farm soil at O'Reilly's Weir near Lake Clarendon, where the erosion at one farm is simply appalling. The big wets of 2011 and 2013 have gouged huge bites out of several sections of the farm. Don't get too close. It is very, very unstable," SEQ Catchments chief executive Simon Warner warned. Chief executive of SEQ Catchments, Simon Warner, explains how attempts to control the path of Blackfellow Creek have failed. It has every chance of just getting worse unless we do something. It will collapse and just be eaten away. Will it stabilise itself? I think not. The rich, rich soil eroded from this farm washes down towards Brisbane, through the Mt Crosby Treatment Plant and eventually into Moreton Bay. Every day. Every night. Top soil washed off farms upstream. In January 2013, Brisbane came within six hours of running out of drinking water after river water "four times muddier than normal" completely blocked the Mt Crosby Treatment Plant. The risk of it happening had been known since 2008. For it to happen again there just needs to be another very big rain cell to sit over the Lockyer Valley and accelerate erosion in the area. Southeast Queensland's summer storm season began a few weeks ago. Near Gatton Darren Jahnke and his family have run a pumpkin farm beside Lower Tenthill Creek for four generations. Water from the January 2011 floods washed over about a fifth of his farm, sending valuable farmland crashing down into Tenthill Creek. In January 2013, Cyclone Oswald pushed the water in the creek even higher. What saved his family a second catastrophe was that between those two weather events, SEQ Catchments helped Mr Jahnke build a tapered and restructured creek bank on top of engineered boulders, and they carefully-replanted eucalypts and ground cover to stabilise the farm's soil. Mr Jahnke said he would have lost a big chunk of his farm, which is tucked into a U-bend of Lower Tenthill Creek, if the work hadn't been done. "I think the creek would have just cut straight across," he said. Mr Jahnke added that by the end of the January 2013 storm season metres of topsoil from other farms upstream had been washed onto his land. "I had to get bulldozers in to flatten it out, there was so much of it," he said. Topsoil is very quietly choking Moreton Bay. Experts say at least, 550,000 tonnes of topsoil would have washed from the Lockyer Valley to Moreton Bay since the January 2011 floods. Even more quietly, erosion is seriously risking the drinking supply of modern, fast-growing Brisbane. Despite this, on October 13 it was revealed the Mt Crosby Water Treatment Plant would not be upgraded. That means Brisbane is relying on Lockyer Valley farmers and growers to prevent erosion and ensure the safety of Brisbane's drinking supply. Next to Laidley Creek, behind the Mulgowie Hotel, Mr Warner pointed out a test site where SEQ Catchments has been replanting hundreds of trees in order put a halt to the problem. A few hundred metres away Mulgowie Farming lost between "16 and 20 inches" of topsoil in January 2013. Mr Warner said topsoil erosion was a problem all growers wanted to address. Meanwhile, Rachel Mackenzie from farming lobby group Growcon, said replanting programs and on the spot advice would work, but it needed to be well coordinated and carried out on a large scale. "Here is a great opportunity to actually do something that benefits the farmers who live in the catchment and benefits all the people who live along the streams," she said. It also benefits the people of Brisbane because they get to have decent drinking water and [it] benefits our beautiful environmental asset in Moreton Bay. I just can't understand why we just aren't putting our foot to the pedal and moving on this. Part of the problem is that there is just so many players in Southeast Queensland and they are all shifting the blame. We actually got the solution and what we want is some decent recurrent funding to start it. We can actually deal with this problem and make it yesterday's problem. Tomorrow: SEQ Catchments' solution