Cumulative Groundwater Impact Assessment and Management – An Example in Practice

Production of coal seam gas (CSG), or coal bed methane, requires large-scale depressurisation of a target formation by extracting groundwater, which, in turn, has the potential to affect overlying and underlying aquifers. This leads to wide-ranging stakeholder concerns around the impacts on groundwater assets such as water supply bores, groundwater-dependent ecosystems and connected watercourses. Around 2010, the CSG industry in Queensland, Australia grew rapidly with the expansion of operations in the Surat and Bowen basins by multiple operators. This particularly raised concerns about the cumulative effects, because the target coal seams are part of the Great Artesian Basin – one of the world’s largest aquifers. To respond to this challenge, an innovative framework was developed to provide for an independent cumulative impact assessment and to set up arrangements for managing those impacts. This chapter describes the main thrust of that framework.

The Cambodian Mekong floodplain under the future development plans and climate change

Water infrastructure development is crucial for driving economic growth in the developing countries of the Mekong. Yet it may also alter existing hydrological and flood conditions, with serious implications for water management, agricultural production and ecosystem services, especially in the floodplain regions. Our current understanding of the hydrological and flood pattern changes associated with infrastructural development still contain several knowledge gaps, such as the consideration of overlooked prospective drivers, and the interactions between multiple drivers. This research attempts to conduct a cumulative impact assessment of flood changes in the Cambodian part of the Mekong floodplains. The developmental activity of six central sectors (hydropower, irrigation, navigation, flood protection, agricultural land use and water use) as well as climate change were considered in our modelling analysis. Our results show that the monthly, sub-seasonal, and seasonal hydrological regimes will be subject to substantial alterations under the 2020 planned development scenario, and even larger alterations under the 2040 planned development scenario. The degree of hydrological alteration under the 2040 planned development is somewhat counteracted by the effect of climate change, as well as the removal of mainstream dams in the Lower Mekong Basin and hydropower mitigation investments. The likely impact of decreasing water discharge in the early wet season (up to −34 %) will pose a critical challenge to rice production, whereas the likely increase in water discharge in the mid-dry season (up to +54 %) indicates improved water availability for coping with drought stresses and sustaining environmental flow. At the same time, these changes would have drastic impacts on total flood extent, which is projected to decline up to −18 %, having potentially negative impacts on floodplain productivity whilst at the same time reducing the flood risk to the area. Our findings urge the timely establishment of adaptation and mitigation strategies to manage such future environmental alterations in a sustainable manner.