3.1 Water availability and supply

3.1.1        Tapping water from rivers and lakes for European cities

Public water supply accounts for 32% of the total water use in Europe (EEA, 2016b). This is, roughly a third of the total freshwater abstracted in Europe is directed to households, small businesses, hotels, offices, hospitals, schools and some industries. Some of the main challenges faced by urban water supply include droughts, water scarcity, seasonal or geographical mismatches between water availability and water demand, and low efficiency of water distribution networks (including leakage). In some European countries these challenges have led to overexploitation and pollution of groundwater resources, as falls in the piezometric level of aquifers can give way to higher pollutant concentrations and salt water intrusion (the latter in coastal aquifers). This has subsequently resulted in the implementation of measures ranging from the softer – like awareness-raising campaigns – to the more drastic – like abstraction restrictions (De Paoli et al., 2016) and water transfers between different river basins.   

To secure a reliable and safe water supply, cities have typically developed centralised systems to abstract, transfer and distribute water. Urban uses of water, including the necessary hydraulic interventions to secure a regular supply, are transforming considerably the natural ecosystems within and close to cities and are in competition with other water uses (e.g. recreation, irrigation etc). In turn, these other uses affect the availability of the resource for urban use by impacting on its quality (Kallis & Coccossis, 2001).

With growing populations and increasing demand for water, Europe’s larger cities have generally relied on the surrounding regions for drinking water supply, mostly supplied by groundwater but sometimes by surface waters. For example, Athens, Istanbul and Paris are all cities which have developed wide networks for transporting water, often over more than 100-200 km, to their water-hungry densely-populated cities. Even in Germany, which is a relatively water-rich country, water is being transported over long distances to supply urban centres. This is the case for the city of Stuttgart which receives its drinking water from Lake Constance, located at a distance of 160 km.

There are also other European cities that depend on lake surface waters for their drinking water supply such as the city of Tallinn. The city of Tallinn uses Lake Ülemiste as its main drinking water reservoir and has been applying several measures to protect and improve water quality in the lake.

3.1.2        Towards a more sustainable water supply in cities

Considering that water around large cities is often polluted and cannot be used as potable water, a number of factors should be taken into account when seeking to reduce the vulnerability of large cities to water stress. These factors may include growing urban populations, improving lifestyles, reduced water availability due to climate change and the introduction of drinking water quality standards (EEA 2010).

The design of urban water supply infrastructure rests on a dominant engineering and supply-led approach in managing water dating back to the first stage of urban development and industrialisation. This is now considered outdated in an era of regional and global inter-dependence, technological development, economic restructuring and unprecedented flow of people, goods and resources (Kallis & Coccossis, 2001).

While centralized water systems have, in general, ensured adequate water supply, sanitation and drainage services in cities around the world (Sitzenfrei et al., 2013), several factors such as climate change, increasing water supply and consumption, as well as ageing water and wastewater infrastructures increasingly pose maintenance challenges to the cities.

To prevent urban water crises, water resources should be managed effectively at every stage: from the supply of clean water to its different uses by the consumers. This could involve reducing consumption (e.g. by means of technological improvements, water pricing schemes and non-pricing approaches to manage water demand) as well as finding new ways of collecting and using water (e.g. re-using rain and grey water) and reuse treated wastewater. Water management should also be better integrated within wider urban management while taking into account characteristics of the local environment (EEA, 2012c).

For instance, only a minor fraction of the high quality potable water provided by the centralized systems is currently used for potable purpose and most of the potable water is used for applications with low water quality requirements such as toilet flushing and garden irrigation. Under such conditions, the centralized water service model with the bulk transfer of freshwater and the bulk disposal of wastewater is not always the most sustainable solution for urban development (van Roon 2007). Decentralized water management is a concept in which water is managed, collected, treated and disposed/reused near or at the point of generation (Crites and Tchobanoglous 1998). Decentralized systems are increasingly considered to be implemented for two purposes; (1) to reduce flows to centralized wastewater treatment systems and (2) to provide opportunities for the wastewater reuse and recycling at the local level (Diaper et al., 2007).

One of the non-technological, non-pricing measures to manage water demand in large cities are awareness-raising campaigns. This approach has been used in Europe as a prevention measure as well as an emergency measure in the context of severe drought (e.g. during the severe drought that hit Barcelona in 2007-2008 (Martin-Orega and Markandya, 2009)). Given that this type of measures commonly aim at influencing household behaviour, their actual effectiveness is difficult to assess. Nonetheless, there have been interesting cases where the measures implemented could be directly associated to large scale shifts in water demand. Furthermore, when used in combination with other water demand measures, the overall effect can be stronger. For example, accompanying the promotion of water-saving technologies with educational campaigns that highlight their functionality and the appropriate way to use them can enhance the effect of the former (Cominola et al., 2015). The case of the project Zaragoza: Water Saving City is one that has resonated throughout Europe, evidencing the potential of a carefully structured awareness-raising campaign with clearly defined, concrete targets.