A preliminary feasibility study for a backup water supply- coastal reservoir in Southeast Queensland, Australia Shu-Qing Yang ABSTRACT Australia is the driest inhabited continent in the world, and Southeast Queensland has experienced extreme water scarcity. Intensive research has been conducted and many solutions have been proposed in order to secure its water supply, such as more inland reservoirs, wastewater recycle and reuse, and desalination plants, etc., but after the Millennium drought some of these measures are not readily accepted by the public and government, thus alternative water sources to secure its future demands are urgently needed. By analyzing the natural conditions it is found that coastal reservoirs could be useful for this region, and their feasibility is discussed and analyzed. The new solution is compared with previous proposals based on their sustainability, impacts on environment and ecosystem, construction and operation cost, and greenhouse gas emission. It is found that the strategy of coastal reservoirs meets the regional water demand well, and it is sustainable, environmentally friendly and cost-effective. Most importantly, the example shows that the proposed strategy may eliminate the need of desalination in other runoff-rich regions in the world. Shu-Qing Yang School of Civil, Mining and Environmental Engineering, University of Wollongong, Wollongong, NSW 2522, Australia E-mail: shuqing@uow.edu.au Key words | coastal reservoir, desalination plants, stormwater harvesting, water crisis, water pollution INTRODUCTION Water is one of the most important resources, and clean water has been and continues to be one of the major chal- lenges for human society. The world’s water supplies are facing threats due to population growth and economic development, thus the access to clean water was selected as one of the great challenges for the 21st century by the National Academy of Engineering, USA. This is understand- able, as in 2013 UN-Water declared that 1,800 million people will live in countries with absolute water scarcity by 2025 and two-thirds of the world’s population could be under severe water stress conditions. To meet the crop demand projected for 2025, an additional 192 cubic miles of water per year could be required – a volume nearly equiv- alent to the annual flow of the Nile 10 times over (Gleick ). Therefore, water shortage is a major socio-economic problem facing society today and will soon become one of the major constraints for future economic development. Severe water shortages have particularly struck arid and semi-arid areas like Australia where it is often said that the story of Australia is the story of the search for and use of water. Australia is the driest inhabited continent on Earth (Donohue et al. ). Its semi-arid area (annual rainfall is less than 600 mm) makes up about 80% of the mainland and the arid area (annual rainfall <300 mm) covers 60% of the total 7.7 million km 2 which is almost the same size as the USA (excluding Alaska). Its long-term average rainfall across the whole country is 457 mm, on average, 90% of its rainfall is directly evaporated back to the atmosphere due to the dry climate; only 10% becomes runoff into rivers or recharge into groundwater aquifers. The variability of spatial and temporal rainfall in Australia is high, it may vary from zero for several years to extreme hydrological events, e.g., 515 mm in 6 hours at Dapto, New South Wales in 1984 (Chanson ). Most rainfall events occur in a wet season associated with intense fall, and the rest of the year is very 470 © IWA Publishing 2015 Journal of Water Supply: Research and Technology—AQUA | 64.4 | 2015 doi: 10.2166/aqua.2015.103 Downloaded from https://iwaponline.com/aqua/article-pdf/64/4/470/399953/jws0640470.pdf by guest on 22 July 2020