Using subsurface temperatures to derive the spatial extent of the land use change effect

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The urban heat island (UHI) effect has traditionally been determined using ambient air temperatures or land surface temperatures derived from satellite observations. In this study, we used the subsurface temperature anomaly as an indicator in describing a relationship between land use characteristics and aquifer temperature changes in the shallow subsurface layers of three rapidly developing urban settings: the Kanto, Sendai and Chikushi plains in Japan. Information on land cover was derived from Landsat Enhanced Thematic Mapper Plus (ETM+) images acquired between 1999 and 2001. The supervised classification technique along with the Normalized Difference Vegetation Index (NDVI) was used to specify the urban degree for grid cells covering observation wells. Preliminary analysis of groundwater levels in different well locations revealed that vertical groundwater recharge is predominant in all study areas. A numerical model for subsurface heat transport employed with different groundwater recharge/discharge and ground surface warming rates indicated that ground surface warming has a significant effect on aquifer temperatures in shallow subsurface layers. The results show that the magnitude of aquifer temperature change is positively correlated with the degree of impervious area derived from the NDVI values (i.e., negatively correlated with the NDVI value with 0.5-0.7°C warming for a 0.12NDVI difference at a 20-m depth). The relationship between aquifer temperature changes and grid-averaged NDVI values was strongest at an area of approximately 99,225m 2 (roughly equal to an area with a 175-m radius) and determination coefficient equal to 0.91 for the Kanto plain. As the average area is further increased, the relationship between the two variables gradually became weaker. According to results verified for the Sendai and Chikushi plains, the same relationship was achieved for areas no larger than 175 (±15)m radius and a determination coefficient of 0.81, which is suggested as the operational spatial scale to determine the UHI effect on subsurface thermal regimes. As the necessity for adaptation measures to cope with urban thermal pollution is increasingly understood, the lateral extent of subsurface heat flow found in this study may be useful in urban planning and habitat restoration programs.

Original languageEnglish
Pages (from-to)40-51
Number of pages12
JournalJournal of Hydrology
Volume460-461
DOIs
Publication statusPublished - Aug 16 2012

Fingerprint

NDVI
land use change
aquifer
warming
heat island
groundwater
recharge
temperature
thermal pollution
habitat restoration
urban pollution
thermal regime
subsurface flow
image classification
urban planning
temperature anomaly
heat flow
ambient air
Landsat
land surface

Keywords

  • Aquifer temperature
  • Japan
  • NDVI
  • Spatial extent
  • Urban heat island

ASJC Scopus subject areas

  • Water Science and Technology

Cite this

Using subsurface temperatures to derive the spatial extent of the land use change effect. / Gunawardhana, Luminda Niroshana; Kazama, So.

In: Journal of Hydrology, Vol. 460-461, 16.08.2012, p. 40-51.

Research output: Contribution to journalArticle

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abstract = "The urban heat island (UHI) effect has traditionally been determined using ambient air temperatures or land surface temperatures derived from satellite observations. In this study, we used the subsurface temperature anomaly as an indicator in describing a relationship between land use characteristics and aquifer temperature changes in the shallow subsurface layers of three rapidly developing urban settings: the Kanto, Sendai and Chikushi plains in Japan. Information on land cover was derived from Landsat Enhanced Thematic Mapper Plus (ETM+) images acquired between 1999 and 2001. The supervised classification technique along with the Normalized Difference Vegetation Index (NDVI) was used to specify the urban degree for grid cells covering observation wells. Preliminary analysis of groundwater levels in different well locations revealed that vertical groundwater recharge is predominant in all study areas. A numerical model for subsurface heat transport employed with different groundwater recharge/discharge and ground surface warming rates indicated that ground surface warming has a significant effect on aquifer temperatures in shallow subsurface layers. The results show that the magnitude of aquifer temperature change is positively correlated with the degree of impervious area derived from the NDVI values (i.e., negatively correlated with the NDVI value with 0.5-0.7°C warming for a 0.12NDVI difference at a 20-m depth). The relationship between aquifer temperature changes and grid-averaged NDVI values was strongest at an area of approximately 99,225m 2 (roughly equal to an area with a 175-m radius) and determination coefficient equal to 0.91 for the Kanto plain. As the average area is further increased, the relationship between the two variables gradually became weaker. According to results verified for the Sendai and Chikushi plains, the same relationship was achieved for areas no larger than 175 (±15)m radius and a determination coefficient of 0.81, which is suggested as the operational spatial scale to determine the UHI effect on subsurface thermal regimes. As the necessity for adaptation measures to cope with urban thermal pollution is increasingly understood, the lateral extent of subsurface heat flow found in this study may be useful in urban planning and habitat restoration programs.",
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