Water temperature is often monitored at water sources and treatment works; however, there is limited monitoring of the water temperature in the drinking water distribution system (DWDS), despite a known impact on physical, chemical and microbial reactions which impact water quality. A key parameter influencing drinking water temperature is soil temperature, which is influenced by the urban heat island effects. This paper provides critique and comprehensive summary of the current knowledge, policies and challenges regarding drinking water temperature research and presents the findings from a survey of international stakeholders. Knowledge gaps as well as challenges and opportunities for monitoring and research are identified. The conclusion of the study is that temperature in the DWDS is an emerging concern in various countries regardless of the water source and treatment, climate conditions, or network characteristics such as topology, pipe material or diameter. More research is needed, especially to determine (i) the effect of higher temperatures, (ii) a legislative limit on temperature and (iii) measures to comply with this limit.

The water temperature in the drinking water distribution system and at customers' taps approaches the surrounding soil temperature at a depth of 1 m. Water temperature is an important determinant of water quality. In the Netherlands drinking water is distributed without additional residual disinfectant and the temperature of drinking water at customers' taps is not allowed to exceed 25 °C. In recent decades, the urban (sub)surface has been getting more occupied by various types of infrastructures, and some of these can be heat sources. Only recently have the anthropogenic sources and their influence on the underground been studied on coarse spatial scales. Little is known about the urban shallow underground heat profile on small spatial scales, of the order of 10 m × 10 m. Routine water quality samples at the tap in urban areas have shown up locations – so-called hotspots – in the city, with relatively high soil temperatures – up to 7 °C warmer – compared to the soil temperatures in the surrounding rural areas. Yet the sources and the locations of these hotspots have not been identified. It is expected that with climate change during a warm summer the soil temperature in the hotspots can be above 25 °C. The objective of this paper is to find a method to identify heat sources and urban characteristics that locally influence the soil temperature. The proposed method combines mapping of urban anthropogenic heat sources, retrospective modelling of the soil temperature, analysis of water temperature measurements at the tap, and extensive soil temperature measurements. This approach provided insight into the typical range of the variation of the urban soil temperature, and it is a first step to identifying areas with potential underground heat stress towards thermal underground management in cities.

A drinking water distribution system (DWDS) is a critical and a costly asset with a long lifetime. Drinking water demand is likely to change in the coming decades. Quantifying these changes involves large uncertainties. This paper proposes a stress test on the robustness of existing DWDS under changing drinking water demands. The stress test investigates the effects of extreme but plausible demand scenarios on the network performance. Two layouts, one conventional looped designed for fire flows and one designed as a self-cleaning, were tested. For 12 demand scenarios, diurnal patterns were simulated with the end-use model SIMDEUM. The performance of the network was evaluated on three criteria: (1) network pressure, (2) water quality, and (3) continuity of supply. Although the self-cleaning layout had higher head losses, it performed better regarding water quality than the conventional layout. Both networks are robust to the extremities of drinking water demands. The stress test is useful to quanti...

Water infrastructure is inherently a socio-technical system. Rapidly changing urban trends and long-term uncertainties make water infrastructure management complex. This paper analyses the dynamics of residential water consumption in the Netherlands since 1900. During this period, different drivers for change had an influence on residential water use. Results show that different (f)actors and trends had a role in the change of routines, perceptions, expectations, technologies and norms. Drivers of change in residential water consumption were for instance technological developments, the changing perception of comfort and external pressures, such as the oil crisis in the 1970s, and energy labelling of appliances and buildings. These changes led to transitions in the urban system by adjustments in regulative, normative, and cognitive aspects of regimes. In this paper, these transitions are analysed. For instance, full adoption of showers took 60 years, and the maximum annual adoption rate was 6.4% for washing machines. Understanding the links between physical and technological features and society can provide key information about how urban water transitions occur. This knowledge must be used in water infrastructure planning as it impacts demand and typical demand patterns.