This research addresses the issue of rising soil temperatures, driven by climate change. As the Drinking Water Distribution System (DWDS) is located in the sub-surface, the drinking water temperature in the distribution mains attains this rising soil temperature. Because the temperature of drinking water is an important determinant of water quality, Dutch law mandates that drinking water temperature may not exceed 25 °C. This study assesses several measures, including their quantitative impact on soil temperature reduction, and consequently on drinking water temperature reduction. These measures center on modifying the ground coverage, as this measure can be implemented without excavation and disrupting existing infrastructure in the sub-surface. This includes different types of ground coverage (e.g. changing concrete tiles, which are the existing top layer type, to vegetation), and creating temporary shade or applying white paint to the existing coverage type. The effect of (re)locating pipes to a deeper level or in the shade are also considered. The effect at the depth of a distribution main is analysed, which is shallow (0.7 m) in Rotterdam, and 1 m depth in general in the Netherlands.
Measurements confirm the significant influence of the ground coverage, mainly impacting the soil temperature in vertical (in-depth) direction. A detailed analysis reveals the quantitative effectiveness of the considered measures, indicating substantial cooling potential by modifying the ground coverage. Replacing concrete tiles with vegetation (in sandy soil) results in the most cooling effect of all analysed measures. White paint on concrete tiles emerges as particularly effective in reducing the soil temperature at the current depth in Rotterdam (0.7 m), and is considered an easily executable measure to prevent exceedances of the 25 °C threshold, mainly in case of urgency. In general, modifying the top layer as measure is considered feasible. This is because it avoids the need for excavation, in contrast to the alternative measures of relocation to a deeper level or in the shade. Additionally, the study quantifies soil temperature through simulations. A comparative analysis between simulations conducted by the soil temperature model and measurements facilitates an examination of the anticipated progression and the predicted effect of measures by the model, allowing for the formulation of recommendations to enhance the model.
As the results indicate that modifications to the ground coverage can significantly contribute to cooling the soil, this can mitigate potential threats to drinking water quality. The study advocates an integrated approach to decision-making, which includes collaboration between municipalities, drinking water companies, and research institutes. This cooperative effort is essential for identifying and implementing the most suitable and effective measures to safeguard high-quality drinking water, both now and in the future.