The Rural Population.

Combining monitoring and modelling tools as a basis for city-scale concepts for a sustainable thermal management of urban groundwater resources.

Comparing anthropogenic heat input and heat accumulation in the subsurface of Osaka, Japan.

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A risk register for energy security: a UK case study

Identifying key locations for shallow geothermal use in Vienna

Low-enthalpy ground source heating systems can help to reduce our dependence on fossil fuels, in turn reducing greenhouse gas emissions and increasing energy security. To de-risk and support the sustainable development, regulation and management of ground source heating systems in urban areas, detailed baseline mapping of groundwater temperatures is required. Groundwater temperatures were measured in 168 monitoring boreholes primarily within a Quaternary sand and gravel aquifer in the city of Cardiff, UK. The data have been used to create the first city-wide map of shallow groundwater temperatures in the UK. This map can be used both to support development of ground source heating and to act as a detailed baseline from which to measure change. Shallow groundwater temperatures under the city were found to be 2°C warmer than the UK average groundwater temperature and this additional heat is attributed to the urban heat island. The zone of seasonal fluctuation varies from 7.1 and 15.5 m below ground level (mbgl) within the shallow Quaternary aquifer, averaging 9.5 mbgl. Deeper groundwater temperature profiles incorporating both the Quaternary and bedrock aquifers suggest that a ‘zone of anthropogenic influence’ exists down to about 70 mbgl.

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Mapping shallow urban groundwater temperatures, a case study from Cardiff, UK

Low-enthalpy ground source heating and cooling is recognized as one strategy that can contribute towards reducing reliance on traditional, increasingly insecure, CO2-intense thermal power generation, as well as helping to address fuel poverty. Development of this technology is applicable in urban areas where high housing density often coincides with the presence of shallow aquifers. In urban areas groundwater temperatures can be elevated owing to the subsurface urban heat island effect. Uptake and development of this technology is often limited by initial investment costs; however, baseline temperature monitoring and characterization of urban aquifers, conducted in partnership with local authorities, can provide a greater degree of certainty around resource and sustainability that can facilitate better planning, regulation and management of subsurface heat. We present a novel high-density, city-scale groundwater temperature observatory and introduce a 3D geological model aimed at addressing the needs of developers, planners, regulators and policy makers. The Cardiff Geo-Observatory measures temperature in a Quaternary aged sand and gravel aquifer in 61 boreholes and at a pilot shallow open-loop ground source heating system. We show that repurposing existing infrastructure can provide a cost-effective method of developing monitoring networks, and make recommendations on establishing similar geo-observatories. Thematic collection: This article is part of the Measurement and monitoring collection available at: https://www.lyellcollection.org/cc/measurement-and-monitoring

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Bernie Williams

Papers

Mapping shallow urban groundwater temperatures, a case study from Cardiff, UK

Establishing an urban geo-observatory to support sustainable development of shallow subsurface heat recovery and storage