Tidal effects on aquifer thermal regime: An analytical solution for coastal ecosystem management

Gunawardhana, Luminda Niroshana; Kazama, So

doi:10.1016/j.jhydrol.2009.08.035

Cited by 12 publications

(22 citation statements)

References 31 publications

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“…In a natural state, seasonal changes in surface air temperature can cause significant oscillations in the shallow subsurface layer, but generally do not continue below the depths of 15 m (Taniguchi, 1994;Gunawardhana and Kazama, 2009). On a long-term time scale, the influence of anthropogenic forces on aquifer temperature has also been realized.…”

Section: Introductionmentioning

confidence: 99%

Statistical and numerical analyses of the influence of climate variability on aquifer water levels and groundwater temperatures: The impacts of climate change on aquifer thermal regimes

Gunawardhana

Kazama

2012

Global and Planetary Change

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Section: Introductionmentioning

confidence: 99%

Statistical and numerical analyses of the influence of climate variability on aquifer water levels and groundwater temperatures: The impacts of climate change on aquifer thermal regimes

Gunawardhana

Kazama

2012

Global and Planetary Change

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“…The qualitative approaches are simple and easy to apply but fail to properly represent hydro-geological processes. In contrast, physically based deterministic methods systematically approximate physical concepts such as the equilibrium of the slope stability and surface water infiltration by applying a set of mathematical formulae, and modeling is done by using physically meaningful parameter set (Gunawardhana and Kazama, 2009b). The model calibration and validation is therefore carried out with comparatively short time series of field measurements.…”

Section: Methodsmentioning

confidence: 99%

Distributed specific sediment yield estimations in Japan attributed to extreme-rainfall-induced slope failures under a changing climate

Ono

Akimoto

Gunawardhana

et al. 2011

Hydrol. Earth Syst. Sci.

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Abstract. The objective of this study was to estimate the potential sediment yield distribution in Japan attributed to extreme-rainfall-induced slope failures in the future. For this purpose, a regression relationship between the slope failure probability and the subsequent sediment yield was developed by using sediment yield observations from 59 dams throughout Japan. The slope failure probability accounts for the effects of topography (as relief energy), geology and hydroclimate variations (hydraulic gradient changes due to extreme rainfall variations) and determines the potential slope failure occurrence with a 1-km resolution. The applicability of the developed relationship was then validated by comparing the simulated and observed sediment yields in another 43 dams. To incorporate the effects of a changing climate, extreme rainfall variations were estimated by using two climate change scenarios (the MRI-RCM20 Ver.2 model A2 scenario and the MIROC A1B scenario) for the future and by accounting for the slope failure probability through the effect of extreme rainfall on the hydraulic gradient. Finally, the developed slope failure hazard-sediment yield relationship was employed to estimate the potential sediment yield distribution under a changing climate in Japan.Time series analyses of annual sediment yields covering 15-20 years in 59 dams reveal that extreme sedimentation events have a high probability of occurring on average every 5-7 years. Therefore, the extreme-rainfall-induced slope failure probability with a five-year return period has a statistically robust relationship with specific sediment yield observations (with r 2 = 0.65). The verification demonstrated that the model is effective for use in simulating specific sediment yields with r 2 = 0.74. The results of the GCM scenarios suggest that the sediment yield issue will be critical Correspondence to: L. N. Gunawardhana (luminda@kaigan.civil.tohoku.ac.jp) in Japan in the future. When the spatially averaged sediment yield for all of Japan is considered, both scenarios produced an approximately 17-18% increase around the first half of the 21st century as compared to the present climate. For the second half of the century, the MIROC and MRI-RCM20 scenarios predict increased sediment yields of 22% and 14%, respectively, as compared to present climate estimations. On a regional scale, both scenarios identified several common areas prone to increased sediment yields in the future. Substantially higher specific sediment yield changes (over 1000 m 3 /km 2 /year) were estimated for the Hokuriku, Kinki and Shikoku regions. Out of 105 river basins in Japan, 96 will have an increasing trend of sediment yield under a changing climate, according to the predictions. Among them, five river basins will experience an increase of more than 90% of the present sediment yield in the future. This study is therefore expected to guide decision-makers in identifying the basins that are prone to sedimentation hazard under a changing climate in order to prepare and implem...

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“…1) emerge from the peripheral mountain regions and flow toward the sea. The Sendai plain is an alluvial formation and serves as the main aquifer of the catchment (detailed information is in Gunawardhana and Kazama 2009). The maximum depth of the aquifer ranges between 60-80 m and is shallow compared with other plains, such as the Kanto Plain (more than 2,000 m) near the Tokyo Metropolitan area.…”

Section: Study Area and Data Collectionmentioning

confidence: 99%

“…The water table usually occurs in a range of 2.5-7.5 m from the ground surface, which is shallow near to the coast and comparatively deep when the distance from the coast increases (2.5 m in W2 and 7.5 m in W4). Continuous hourly temperature at selected aquifer depths (Gunawardhana and Kazama 2009) and instantaneous groundwater temperature at one-meter intervals Some significant differences in land use types exist at the local scale surrounding the wells. Land use was classified in to 6 categories based on land use map and field surveys.…”

Section: Study Area and Data Collectionmentioning

confidence: 99%

“…Long-term hourly temperature observations (from May, 2007 to July, 2009) in the Sendai plain, taken at different aquifer depths in W1-W4, show that seasonal GST change has no effect at depths below 12 m ( Fig. 3b and Gunawardhana and Kazama 2009). Therefore, the T-D profiles below 12 m can be used for long-term analysis (Taniguchi et al 2003).…”

Section: Analysis Of Aquifer Temperature Recordsmentioning

confidence: 99%

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Impact of Urbanization and Climate Change on Aquifer Thermal Regimes

Gunawardhana

Kazama

Kawagoe

2011

Water Resour Manage

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We evaluated the past impacts of urbanization and climate change on groundwater-in particular, aquifer temperature-in the Sendai plain, Japan, and further compared with the probable changes due to changing climate in the future. A series of simulations were performed and matched with the observed temperaturedepth profiles as a preliminary step for parameter calibration. The magnitude of ground surface warming estimated from subsurface temperature spans 0.9-1.3 • C, which is consistent with the calibrated ground surface warming rates surrounding various observation wells (0.021-0.015 • C/year) during the last 60 years. We estimate that approximately 75% of the ground surface temperature change can be attributed to the effect of past urbanization. For the climate predictions, climate variables produced by the UK Hadley Centre's Climate Model (HadCM3) under the A2, A1B and B1 scenarios were spatially downscaled by the transfer function method. Downscaled monthly data were used in a water budget analysis to account for the variation in recharge and were further applied in a heat transport equation together with the estimated ground surface warming rates in 2080. Anticipated groundwater recharge under the projected climate in 2080 would decrease by 1-26% compared to the 2007 estimates, despite the projected 7-28% increase in precipitation, due to a higher degree of evapotranspiration resulting from a 2.5-3.9 • C increase in surface air temperature. The overall results from the three scenarios predict a 1.8-3.7 • C subsurface temperature change by 2080, which is notably greater than the previous effect of urbanization and climate change on aquifer temperature in the Sendai plain.

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Tidal effects on aquifer thermal regime: An analytical solution for coastal ecosystem management

Cited by 12 publications

References 31 publications

Statistical and numerical analyses of the influence of climate variability on aquifer water levels and groundwater temperatures: The impacts of climate change on aquifer thermal regimes

Statistical and numerical analyses of the influence of climate variability on aquifer water levels and groundwater temperatures: The impacts of climate change on aquifer thermal regimes

Distributed specific sediment yield estimations in Japan attributed to extreme-rainfall-induced slope failures under a changing climate

Impact of Urbanization and Climate Change on Aquifer Thermal Regimes

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