Urban Heat Island effect extends below ground to water sources

Urban Heat Island effect extends below ground to water sources
by Robert Schreiber
Berlin, Germany (SPX) Nov 03, 2023

Urban centers are experiencing a significant but often overlooked phenomenon that impacts the local groundwater temperatures: the warmth emanating from underground car parks. Recent investigations have uncovered that these concrete structures, designed for vehicle storage, inadvertently act as a source of heat pollution, elevating the temperature of the surrounding subterranean environment.

The interplay between urban infrastructure and the natural environment is complex, and as cities continue to expand, the effects of construction and development on ecosystems receive increased scrutiny. One of the latest insights into this dynamic is the discovery of underground car parks as contributors to the rise in groundwater temperatures, which has potential implications for urban sustainability and infrastructure planning.

Groundwater is a crucial resource, serving not only as a source of drinking water but also as a component of the urban ecosystem that influences the health of vegetation and urban green spaces. The warmth from car parks, primarily due to the accumulation of heat from the earth above and waste heat from vehicles, seeps into the groundwater, creating a thermal footprint that extends beyond the immediate vicinity of the structures.

This revelation is not isolated; it aligns with a larger pattern recognized within urban landscapes known as the urban heat island effect. Typically discussed in the context of above-ground temperatures, the effect is characterized by elevated temperatures in urban areas compared to their rural surroundings, resulting from the concentration of buildings, vehicles, and human activity. The new findings suggest that this heat island effect also permeates below the surface, affecting groundwater reserves.

The consequences of this underground heating are multifaceted. Ecologists and city planners are especially concerned about the disruption to local ecosystems. Aquatic species, which are sensitive to temperature changes, could be adversely affected. Furthermore, the increase in groundwater temperatures can impact the efficacy of geothermal heating and cooling systems, which rely on consistent underground temperatures.

Another point of consideration is the potential for increased energy consumption. As groundwater temperatures rise, the energy required for cooling buildings, particularly during the summer months, could surge, leading to higher electricity demand and associated carbon emissions. The findings underscore the interconnected nature of urban infrastructure and the environment, where even underground constructions can have far-reaching impacts on sustainability goals.

This phenomenon has been observed and measured in a European context, with the city of Cologne, Germany, serving as a case study. In Cologne, groundwater temperatures up to 20 degrees Celsius have been recorded in the vicinity of underground car parks - significantly higher than the average rural groundwater temperatures. It is an indication of the thermal effect that such structures, often considered benign to subterranean environments, can have.

City officials and urban planners are taking note of these findings, as the implications for city planning and environmental policies could be substantial. Strategies for mitigating the impact of urban infrastructure on groundwater temperatures may become a necessary component of sustainable urban development. This could involve the design and construction of car parks with improved ventilation and materials that mitigate heat retention.

The research into this area is ongoing, with scientists aiming to understand the full scope of the effects of subterranean structures on the environment. They are also seeking to develop a comprehensive picture of how urban development patterns influence groundwater systems. This includes assessing the long-term implications for groundwater quality and availability, vital for ensuring the resilience of urban water supplies.

The emerging recognition of the thermal influence of underground car parks on groundwater supplies is a call to action for sustainable city planning. It emphasizes the need for a holistic approach to urban development that considers not only the visible impacts of construction but also the unseen effects on natural resources. It is a critical component of future-proofing cities against the unintended consequences of their growth and ensuring that environmental considerations are at the forefront of urban development strategies.

Research Report:Thermal impact of underground car parks on urban groundwater