Rapid groundwater warming in an eastern mediterranean coastal aquifer linked to urbanization

Urban heat redistribution is mainly result of surface energy process. Surface energy process is also contributed in urban environment. Urban heat island (UHI) is mainly defined when urban temperature is elevated compared to surrounding rural area. Both in above and below the ground UHI is observed. This is happened due to conductive heat transport. How the Land surface temperature and ground water temperature are affected by the urban land use in Bangalore is the primary plan of investigation. Landsat data of 1999 and 2009 are used to understand the LU/LC changes. In this present study we used satellite derived Land surface temperature and field collected Ground water temperature which was analyzed using interpolation method and Supervised Classification Change Detection technique applied for change analysis. Here investigation was done for a period of one decade (1999/2009) on LST changes over different land use. Moreover, relationship between NDVI and LST was also considered. To understand urban surface, we estimated Normalized Difference Built-Up Index (NDBI) and Built up Area Index (BUAI); with this we are trying to find relationship with ground water temperature. Changing land use pattern, mostly expansion of built-up area has effect over land surface temperature in Bangalore urban district. The correlation between LST and the Ground water temperature (GWT); has been studied on 2009 data and found 80% correlation between them. In result, it is showing that GWT is less than LST but wherever LST is high there GWT is also high. In city core area like residential, outside industrial and road, GWT and LST both show high but near to lake or park area both show low temperature. Results show that during years 1999 to 2009 that LST and GWT directly affected due to rapid urban growth which reflects over built-up area enlarged from 39 to 57%. We can understand that urbanization has an impact on both on LST and GWT. The study showed that land use land cover change has important role of increasing GWT which is a marker of the strength of urban heat island effect and can be utilized to evaluate the extent of the urban heat island effect.KeywordsGround water temperatureLand surface temperatureBuilt up area indexSub surface urban heat islandRemote sensing

Climate change effects on groundwater recharge and temperatures in Swiss alluvial aquifers

Urban temperatures are typically, but not necessarily, elevated compared to their rural surroundings. This phenomenon of urban heat islands (UHI) exists both above and below the ground. These zones are coupled through conductive heat transport. However, the precise process is not sufficiently understood. Using satellite-derived land surface temperature and interpolated groundwater temperature measurements, we compare the spatial properties of both kinds of heat islands in four German cities and find correlations of up to 80%. The best correlation is found in older, mature cities such as Cologne and Berlin. However, in 95% of the analyzed areas, groundwater temperatures are higher than land surface temperatures due to additional subsurface heat sources such as buildings and their basements. Local groundwater hot spots under city centers and under industrial areas are not revealed by satellite-derived land surface temperatures. Hence, we propose an estimation method that relates groundwater temperatures to mean annual land-surface temperatures, building density, and elevated basement temperatures. Using this method, we are able to accurately estimate regional groundwater temperatures with a mean absolute error of 0.9 K.

Due to the scarcity of air temperature (Ta) observations, urban heat studies often rely on satellite-derived Land Surface Temperature (LST) to characterise the near-surface thermal environment. However, there remains a lack of a quantitative understanding on how LST differs from Ta within urban areas and what are the controlling factors of their interaction. We use crowdsourced air temperature measurements in Sydney, Australia, combined with urban landscape data, Local Climate Zones (LCZ), high-resolution satellite imagery, and machine learning to explore the influence of urban form and fabric on the interaction between Ta and LST. Results show that LST and Ta have distinct spatiotemporal characteristics, and their relationship differs by season, ecological infrastructure, and building morphology. We found greater seasonal variability in LST compared to Ta, along with more pronounced intra-urban spatial variability in LST, particularly in warmer seasons. We also observed a greater temperature difference between LST and Ta in the built environment compared to the natural LCZs, especially during warm days. Natural LCZs (areas with mostly dense and scattered trees) showed stronger LST-Ta relationships compared to built areas. In particular, we observe that built areas with higher building density (where the heat vulnerability is likely more pronounced) show insignificant or negative relationships between LST- Ta in summer. Our results also indicate that surface cover, distance from the ocean, and seasonality significantly influence the distribution of hot and cold spots for LST and Ta. The spatial distribution for Ta hot spots does not always overlap with LST. We find that relying solely on LST as a direct proxy for the urban thermal environment is inappropriate, particularly in densely built-up areas and during warm seasons. These findings provide new perspectives on the relationship between surface and canopy temperatures and how these relate to urban form and fabric.

Identifying anthropogenic anomalies in air, surface and groundwater temperatures in Germany.

Subsurface temperature data is usually only accessible as point information with a very limited number of observations. To spatialize these isolated insights underground, we usually rely on interpolation methods. Unfortunately, these conventional tools are in many cases not suitable to be applied to areas with high local variability, like densely populated areas, and in addition are very vulnerable to uneven distributions of wells. Since thermal conditions of the surface and shallow subsurface are coupled, we can utilize this relationship to estimate shallow groundwater temperatures from satellite-derived land surface temperatures. Here, we propose an estimation approach that provides spatial groundwater temperature data and can be applied to natural, urban, and mixed environments. To achieve this, we combine land surface temperatures with anthropogenic and natural processes, such as downward heat transfer from buildings, insulation through snow coverage, and latent heat flux in the form of evapotranspiration. This is demonstrated for the city of Paris, where measurements from as early as 1977 reveal the existence of a substantial subsurface urban heat island (SUHI) with a maximum groundwater temperature anomaly of around 7 K. It is demonstrated that groundwater temperatures in Paris can be well predicted with a root mean squared error of below 1 K by means of satellite-derived land surface images. This combined approach is shown to improve existing estimation procedures that are focused either on rural or on urban conditions. While they do not detect local hotspots caused by small-scaled heat sources located underground (e.g., sewage systems and tunnels), the findings for the city of Paris for the estimation of large-scale thermal anomalies in the subsurface are promising. Thus, the new estimation procedure may also be suitable for other cities to obtain a more reliable insight into the spatial distribution of urban ground and groundwater temperatures.

HighlightsWhat are the main findings?Bangalore’s built-up area increased from 7.61% to 28.78% during the period from 1999 to 2017, causing a rise in the land surface temperature (LST) and anthropogenic heat flux (>65 W/m2). There was a rise in temperature (LST) of ~6 °C in green areas and >3 °C in urban areas.Groundwater temperature was strongly correlated with heat flux (R2 = 0.83) and with LST (R2 = 0.78), indicating subsurface warming due to urbanization.What is the implication of the main finding?Sustainable urban planning is needed to reduce the heat stress by increasing the extent of green spaces, adopting cool roofing, and improving water resource management.Incorporating urban heat assessment in policies can enhance thermal comfort, reduce heat-related illness and mortality, mitigate groundwater warming, and ensure long-term water and energy sustainability in rapidly urbanizing cities, such as Bangalore.The continuous expansion of impervious surfaces replacing the vegetation cover and surface water areas increases urban heating. Such heating leads to downward heat transfer and latent heat flux from the surface to subsurface aquifers. This study used Landsat optical and thermal satellite data for land use/land cover (LULC), land surface temperature (LST), and anthropogenic heat flux (Has) change mapping in Bangalore City, India. The in situ sensor-based land surface temperature (LST) and groundwater temperature (GWT) measurements were used to validate the study outcome. A minor difference was observed between the satellite data and the in situ LST due to the differential data acquisition time. The built-up area increased from 7.61% to 28.78% from 1999 to 2017 at the cost of the green cover and the extent of waterbodies. Therefore, LST change was higher in green cover areas (~6 °C LST) than in urban areas (>3 °C). The anthropogenic heat fluxes increased significantly (above 65 W/m2) during the study period. The in situ GWT was strongly correlated with the Has (R2 = 0.83) and LST (R2 = 0.78). The study highlights the nature of urban expansion in Bangalore City, India, and its impact on LST, Has, and GWT. The observed changes in land use practices with urban heat indicators at 30 m scale can be used for sustainable land use planning to improve the thermal comfort of the city, preserving the urban ecosystems. The high collinearity between satellite-data-derived LST, Has, and GWT can be used for periodic monitoring at seasonal and annual scales using the Landsat data, which can be important inputs for land use planners and policymakers.

Coastal aquifers are host to a range of biogeochemical reactions that alter groundwater‐derived nutrient, metal, and other chemical loads to coastal ecosystems. Temperature is a strong control on microbially mediated reactions; thus, chemical reactivity in coastal aquifers may vary spatially and temporally with changes to groundwater temperature. In this study, we investigated the influence of global groundwater and sea surface temperature controls and seasonal temperature variability on biogeochemical processing in coastal aquifers using variable‐density groundwater flow, heat transport, and reactive transport models. The coupled models showed that nitrate removal efficiency in coastal aquifers increased from 5% to 88% as fresh groundwater temperature increased from 5°C to 35°C, while ocean temperature had a negligible effect on removal efficiency. Transient simulations based on monthly groundwater and ocean temperature measurements showed that denitrification and ammonification hotspots migrated seaward seasonally within warm fresh groundwater masses. The reaction hotspots were separated by colder groundwater emplaced during winter months. The reaction hotspots and nitrate plumes oscillated vertically along horizontal flow paths due to buoyancy effects between warm and cold groundwater. Comparison between transient and temperature‐equivalent steady‐state models suggests that steady‐state models adequately capture mean annual NO3− removal, but neglect local reactive transience and changes to plume geometry. The sensitivity analysis provides a first‐order estimate of the reactive potential of coastal aquifers considering globally diverse thermal regimes. The findings have implications for regional‐scale estimates of groundwater nutrient fluxes and for predicting coastal aquifer reactivity in a warming climate.

Variability in annual temperature cycle in the urban areas of the United States as revealed by MODIS imagery

Temperature has been found to play an important role in controlling groundwater flow and salinity distribution in coastal aquifers. However, previous studies focused on the effects of fixed temperature. In nature, both land surface temperature and seawater temperature fluctuate seasonally. The yearly fluctuation ranges of land surface and seawater temperatures can commonly reach 30°C. These surface temperature signals could propagate into coastal aquifers and change the temperature distribution in coastal aquifers. This may further induce seasonal variations in groundwater flow and solute transport processes. This research aims to investigate the effects of seasonal fluctuation in land surface and seawater temperatures on salinity distribution and water exchange in coastal unconfined aquifers subject to semi-diurnal tide. A numerical model, SUTRA-MS, is used to simulate the variably saturated and density-dependent groundwater flow coupled with salt and heat transport. Salt mass stored in the aquifer and water fluxes across the aquifer-ocean interface are used to evaluate the effects. Sensitivity analyses of fluctuation amplitude of temperature and tidal amplitude are also conducted. Finally, we discuss the implications of these results for nearshore biogeochemical processes and for accurate assessment of submarine groundwater discharge.

Research Article| February 01, 2012 Transient change in groundwater temperature after earthquakes Chi-yuen Wang; Chi-yuen Wang 1Earth & Planetary Science, University of California, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Michael Manga; Michael Manga 1Earth & Planetary Science, University of California, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Chung-Ho Wang; Chung-Ho Wang 2Institute of Earth Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan Search for other works by this author on: GSW Google Scholar Chieh-Hung Chen Chieh-Hung Chen 2Institute of Earth Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan Search for other works by this author on: GSW Google Scholar Author and Article Information Chi-yuen Wang 1Earth & Planetary Science, University of California, Berkeley, California 94720, USA Michael Manga 1Earth & Planetary Science, University of California, Berkeley, California 94720, USA Chung-Ho Wang 2Institute of Earth Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan Chieh-Hung Chen 2Institute of Earth Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan Publisher: Geological Society of America Received: 20 Jun 2011 Revision Received: 25 Aug 2011 Accepted: 12 Sep 2011 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2012 Geological Society of America Geology (2012) 40 (2): 119–122. https://doi.org/10.1130/G32565.1 Article history Received: 20 Jun 2011 Revision Received: 25 Aug 2011 Accepted: 12 Sep 2011 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Chi-yuen Wang, Michael Manga, Chung-Ho Wang, Chieh-Hung Chen; Transient change in groundwater temperature after earthquakes. Geology 2012;; 40 (2): 119–122. doi: https://doi.org/10.1130/G32565.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Postseismic decrease in groundwater temperature was documented on the upper rim of a large alluvial fan near the epicenter of the 1999 Mw 7.5 Chi-Chi earthquake (Taiwan). We use a model of coupled heat transport and groundwater flow, constrained by documented water-level changes, to interpret this change. We show that groundwater temperature is sensitive to earthquake-induced flow and the observed temperature decrease may be explained by increased groundwater discharge due to earthquake-enhanced vertical permeability. The result implies that heat flow near active mountain fronts may be lowered by recurrent earthquakes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

<p>The riverside area is suitable for operating the Groundwater Heat Pump (GWHP) system because it has abundant groundwater. In riverside area, inflow of river water can occur due to the hydraulic gradient between the river water and the groundwater. The mixing of the two waters can cause changes of groundwater temperature. Because GWHP systems use a stable temperature of groundwater as the heat source, groundwater temperature changes can affect operational efficiency. Therefore, in order to operate the GWHP system in the riverside region, it is important to understand how the mixing of river water and groundwater affects the groundwater background temperature. In addition, the temperature of groundwater re-injected into the aquifer after heat exchange in the GWHP system can also affect the background groundwater temperature. In this study, 3D groundwater flow and heat transport modeling was conducted based on groundwater and river water level and temperature monitoring data in order to investigate the mixing of river water and groundwater. Solute transport model was used to calculate the mixing ratio of river water and groundwater to determine whether it affects GWHP system. The model was also used to predict the effects of long-term GWHP system operation in the study area for more than 30 years. The model results predicted the sustainability of the GWHP system by understanding changes in groundwater temperature distribution in the study area.</p>

Several meters of rise in groundwater level with significant changes in groundwater temperature were observed near the epicenter of the 1976 Tangshan earthquake—an intraplate earthquake with a magnitude of M S=7.8 that occurred in northern China. The origin of the groundwater level rise, however, remains a mystery. Studying the groundwater level rise can provide insight into the faulting process and has implications for water resources. In this study, we analyze the indications of the groundwater temperature data on the characteristics of the rising groundwater. The results show that the upward flow was maintained for approximately 5 days, and the depth of the rising groundwater was about 1–2 km. We then examine the groundwater level and temperature data with several reported models in order to explain the cause of the groundwater level rise. The results indicate that the groundwater level rise is attributable to the earthquake-induced enhancement of vertical hydraulic connection between the shallow and deep aquifers, leading to the upwelling of deep fluids that causes the groundwater levels to rise.

Urban areas are major contributors to the alteration of the local atmospheric and groundwater environment. The impact of such changes on the groundwater thermal regime is documented worldwide by elevated groundwater temperature in city centers with respect to the surrounding rural areas. This study investigates the subsurface urban heat island (SUHI) in the aquifers beneath the Milan city area in northern Italy, and assesses the natural and anthropogenic controls on groundwater temperatures within the urban area by analyzing groundwater head and temperature records acquired in the 2016–2020 period. This analysis demonstrates the occurrence of a SUHI with up to 3 °C intensity and reveals a correlation between the density of building/subsurface infrastructures and the mean annual groundwater temperature. Vertical heat fluxes to the aquifer are strongly related to the depth of the groundwater and the density of surface structures and infrastructures. The heat accumulation in the subsurface is reflected by a constant groundwater warming trend between +0.1 and + 0.4 °C/year that leads to a gain of 25 MJ/m2 of thermal energy per year in the shallow aquifer inside the SUHI area. Future monitoring of groundwater temperatures, combined with numerical modeling of coupled groundwater flow and heat transport, will be essential to reveal what this trend is controlled by and to make predictions on the lateral and vertical extent of the groundwater SUHI in the study area.

Riverbank filtration is used for producing a large amount of groundwater for a long time. The surface water infiltration is accompanied with riverbank filtration and may significantly affect the quality and temperature of pumping water if the pumping well is located nearby the river. A coupled groundwater flow and heat transport model was developed to estimate the influence of surface water on the temperature in pumping well for groundwater heat pump system at the riverbank. The model included the aquifers under river and considered the variation of surface water temperature with season and depth to simulate accurately pumping water temperature. To depict in detail the aquifers and riverbed sediment in contact with the river, the 3D geological model was developed by Geomodeller, and the numerical model was completed by FEFLOW. For model calibration, the simulation results were compared to the measured groundwater level and temperature data in pumping well during 2 years. The result showed high accuracy with the coefficient of determination (R2) of 0.971, root mean square error (RMSE) of 0.211 ℃. Using calibrated model, the groundwater temperature changes in pumping well were predicted for 15 years. The proposed modeling method can be used to estimate the groundwater flow, quality, and temperature change by the surface water infiltration in riverine aquifer.