ABSTRACT
Freshwater has become a scarce and overexploited natural resource in many parts of the world [34]. It has been recognized as a critical global issue and may become the most strategic resource in many areas, especially the arid and semi-arid regions. According to the International Water Management Institute’s report, Australia, California, the Middle East, and the Mediterranean have been regarded as high water stress regions [26]. Likewise, the situation of water pollution and overextraction in Asia and Africa is far from optimistic. Within the next decades, due to continuous economic and population growth, climate change, rapid urbanization, and deteriorating water
quality, water scarcity is likely to be a big constraint to the future food security and environmental sustainability [22,45]. e scientic denitions of water scarcity concepts include [38]: Water scarcity is the general collective term when water is scarce for whatever reason. Water stress is linked to diculties in water use due to accessibility or mobilization problems (e.g., water infrastructures, ow control, costs). Normally, the use-to-availability ratio with values larger than 40% denotes high water stress. Water shortage refers to population-driven physical shortage of water when seen in relation to principal water requirements:
• Green water shortage, relating to deciency in relation to crop water requirements
18.1 Introduction ............................................................................................................................ 209 18.2 Coping with Freshwater Scarcity by Water Reuse .............................................................. 210
18.4 Summary and Conclusions .................................................................................................... 215 References ............................................................................................................................................. 216
Preface With the socioeconomic development and population increase, freshwater consumption has increased beyond sustainable levels in many parts of the world. To combat water scarcity issues and environmental-related problems, recycled water has been increasingly considered an important alternative water resource. It can provide a viable opportunity to supplement existing freshwater supplies, alleviate contaminant loads exerted by euent discharge, augment and/or improve the stream ow and wetlands, etc. is chapter examines the alternative water resources and identies the importance as well as historical and current development of water reuse. It focuses on the environmental benets associated with various recycled water applications. e illustrated case studies of recycled water in a number of countries, including Australia, Japan, the United States, Europe, and the Middle East, could be good examples for future projects. Notably, there is also a potential to exploit and develop new end uses of recycled water further in both urban and rural areas. is can contribute largely to freshwater savings, wastewater reduction, and water sustainability.
