Designing a method for assessing the use of produced water from coal seam gas projects to supplement environmental flows

This paper proposes an assessment method for discharge of produced water from coal seam gas (CSG) projects to streams in Australia. Management of produced water is a key issue for the sustainability of the CSG industry. The industry is likely to continue expanding in the future creating pressure to find beneficial uses for produced water. It has been suggested that some produced water, treated to an appropriate level, could be used to augment environmental flows in catchments experiencing water stress. The flow assessment method proposed includes six main stages, from determining discharge requirements of the operator and existing environmental values, to predicting changes in stream condition under discharge scenarios and selecting key indicators for monitoring. The main changes that will be brought about to stream ecosystems from discharge of produced water relate to geomorphology, water quality and hydrology. The extent of these changes and the sensitivity of the environmental values within the system to these changes should be assessed prior to approval of stream discharge of produced water, while operational requirements, such as timing, volumes and release points also need to be considered in a whole-of catchment context. The assessment method is applied to the Glenelg River as a case study to illustrate use of the method; this location was selected as a hypothetical case, purely due to data availability.