diseases, increased regional water stress and higher costs of water treatment. Emerging priority contaminants, such as pharmaceuticals (for example, antibiotics and antimicrobials) and endocrine-disrupting chemicals, are under-regulated and their long-term consequences on human and ecological health remain unclear. Some persistent organic pollutants (sometimes referred to as “forever chemicals”) cannot be removed by current drinking water treatment measures. Diffuse pollution inside cities, from solid waste and lawn fertilizer, and from agricultural fertilizers and pesticides used in rural areas upstream can be regulated to prevent severe degradation of water resources at the local and regional level. In addition to the lack of adequate drainage or flood control infrastructure, solid waste exacerbates hydrological hazards like floods by blocking drainage infrastructure.


Between 1.6 and 2.4 billion people through the world live in river basins that experience water scarcity. This figure has the potential to rise to between 3.1 and 4.3 billion people by 2050, equivalent to 20–30 per cent of the global population (Gosling and Arnell 2016). Demand for water in urban areas is projected to increase by 80 per cent between 2018 and 2050 while total available freshwater will remain more or less constant (Flörke, Schneider and McDonald 2018). In addition to population growth, the economic development that often follows urbanization further increases per capita water use in cities (McDonald et al. 2014). The organization of water governance in urban areas (conventional, integrated or adaptive) can further shape approaches to demand and supply management, including the emphasis on measures such as water use efficiency, water loss reduction and greywater reuse (van den Brandeler, Gupta and Hordijk 2019). As sites of concentrated water demand and political and economic power, cities rely on inter-basin transfers for


52 GEO for Cities


water supplies. However, these can cause water shortages for communities in supply basins and environmental degradation that affects aquatic species (McDonald et al. 2014; van den Brandeler 2020). For example, the access of indigenous communities in the rural hinterlands of Mexico City to their local springs was restricted to in order to pipe water and transfer it to the city (Delgado-Ramos 2015; Aragón-Durand 2019).


Measures to increase the urban water supply, such as inter-basin transfers and dams, can thus aggravate tensions between urban and rural areas, as well as regional tensions (Turton et al. 2006; Mgquba and Majozi 2020). Unregulated groundwater use in and around urban areas typically depletes aquifers, increasing contamination and causing land subsidence and subsequent damage to underground infrastructure such as pipes, as well as to infrastructure above the ground (Chaussard et al. 2014; Minderhoud et al. 2017; Hoekstra, Buurman and van Ginkel 2018). Yet there is a general lack of data on groundwater volumes, quality and flows (Flörke, Schneider and McDonald 2018). Cities also affect rainfall patterns as a result of their artificial thermal properties (the urban heat island effect) and increased particulate matter, which can increase downwind precipitation and the generation of convective summer thunderstorms (McGrane 2016).


3.3.4 Oceans and coasts


In many places around the world, from small island states to megacities, urbanization is largely concentrated along the coast (Tibbetts 2002). This concentration of development impacts the marine and coastal environment at the local, regional and global scales. The local impacts include loss and degradation of coastal habitats and


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