Water Journal : Water Journal November 2011
refereed paper resource management water NOVEMBER 2011 91 Grid include asset failure or unavailability due to planned or unplanned events or water quality pressures from deteriorating raw water quality. These changes are coordinated through the SEQ Water Grid Emergency Response Plan, which directs a coordinated effective response in the event of an emergency. Through this plan, the SEQ Water Grid now has an emergency response process equal to any in Australia. This process leverages the strength of the regional interconnection and capacity of both staff and resources embodied in the water grid. It relies on a structured, well-rehearsed set of protocols underpinning a clear chain of command. While there is scope for improvement, the Queensland Floods Commission of Inquiry found that the existing emergency and disaster planning framework was adequate, and the preparations appropriate. With the SEQ Water Grid Emergency Response Plan in place, all Grid Service Providers through the supply chain have clear, step-by-step guidance on how to respond to SEQ Water Grid emergencies, providing the region with an unprecedented level of readiness. Each Water Grid participant also has its own internal Emergency Response Plan for detailed incident management and asset recovery. Emergency management has been a key focus for all Water Grid participants since 2009, with an extensive testing and training program. In 2010--11 alone, more than 90 people were trained in the emergency response plan and several desktop and test exercises were held to simulate a crisis situation. These training activities provided Water Grid Participants with the necessary skills to successfully respond to an emergency. These skills included both technical and professional staff and relied upon the combined efforts of all Water Grid entities. Decision Support System The SEQ Water Grid Manager is putting in place a new decision support system to inform the development of its six-monthly SEQ Water Grid Operating Strategy and monthly Grid Instructions. Currently, the preferred means of operating the Water Grid is determined by engineers, taking into account a number of separate models. For example, water security impacts of alternative operating modes are assessed using WATHNET. The decision support system will integrate these separate models, enabling better decision making and improved overall outcomes. It will enable more Case Study 2: Water Quality On a more routine basis, the SEQ Water Grid's resilience can also be used to respond to unplanned or external water quality events. This case study demonstrates how this functionality was called upon in late April 2011 in response to a hardness and conductivity event in the Mt Crosby plants' source of intake water, the Mt Crosby Weir. The Mt Crosby Weir is situated along the mid-Brisbane River. Its primary water sources are Lakes Wivenhoe, Somerset and Manchester, and the management of these catchments is the responsibility of the relevant bulk water authority, Seqwater. However, the mid-Brisbane River also receives quantities of water from other minor inputs below the Wivenhoe Dam wall, where catchment management is not possible. These include Black Snake Creek and Lockyer Creek, which are both known to be particularly high in hardness and conductivity. During the April 2011 event, Black Snake Creek appears to have caused the most impact; its hardness exceeded 2,000 mg/L CaCO3 and its conductivity approached 10,000 μS/cm. It is also likely that Lockyer Creek contributed to the event; its hardness averaged around 380 mg/L calcium carbonate (CaCO3) and its conductivity exceeded 1,000 μS/cm. Due to this poor raw water quality, treated water exceeded the Australian Drinking Water Guidelines (ADWG) hardness limit of 200 mg/L CaCO3 (NHMRC 2004) and came close to exceeding the limit for total dissolved solids of 500 mg/L (based on conductivity readings and the ADWG-suggested method for converting total dissolved solids to conductivity). With the Mt Crosby product water's hardness at around 100 per cent higher than average, and conductivity at around 150 per cent higher than average, a strategy to transfer water from elsewhere and blend with the impacted water was enacted. The SEQ Water Grid has been used in this manner previously in response to a methylisoborneol event in the summer of 2009--10, which also impacted on the Mt Crosby intake water (Owens, 2011). The aim of the strategy was to ensure water supplied to the two million people in the Brisbane and Ipswich demand zones remained of the greatest possible quality. In this instance, water of better aesthetic quality was transferred from the Gold Coast region to the Brisbane and Ipswich demand zones through the Southern Regional Water Pipeline. This included an increase of production at the Gold Coast Desalination Plant -- the product water of which continues to be demonstrated as excellent, with hardness averaging tightly around 55 mg/L CaCO3 and conductivity around 110 μS/cm (SEQ Water Grid Manager, 2011). Within 24 hours of the event being recognised, the desalination plant ramped up production to 50 ML/d. This water was transferred through the Southern Regional Water Pipeline to Brisbane. Transfers also included water from the Molendinar WTP, and to a lesser extent the Mudgeeraba WTP. In practice, water transferred through the Southern Regional Water Pipeline is blended with water from the Mt Crosby plants at a point before being supplied to Queensland Urban Utilities for distribution to Brisbane and Ipswich. Hence, all water received by consumers was the blended product, optimised around the SEQ Water Grid's operational, financial and water quality constraints. While it is possible for the Southern Regional Water Pipeline to transfer a greater volume of water, it would necessitate a significant increase in production of the desalination facility, to well above baseline levels. Although this could be easily and quickly performed in extreme emergencies, it was deemed an unnecessary expense in an instance such as this, a moderate aesthetic event. The extent to which the SEQ Water Grid's resilience is called upon must always be optimised in context of the aforementioned constraints.
Water Journal December 2011
Water Journal September 2011