Impact of Urbanization and Climate Change on Aquifer Thermal Regimes

Abstract

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.

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

“…In the absence of a strong groundwater flow, this phenomenon produces an approximately linear temperature-depth (T-D) profile within homogeneous depth intervals (e.g., 5 mm/year reported by Majorowicz et al (2006)). When the vertical groundwater flow is comparatively large (e.g., 200 mm/year, as reported in Gunawardhana et al, 2011), the curvature of the temperature-depth profiles changes accordingly. In the presence of a horizontal groundwater flow, the temperature-depth profiles do not exhibit increasing temperature with increasing depth; instead, over a specific depth range, temperatures may decrease or remain constant with increasing depth (e.g., Figs.…”

A water availability and low-flow analysis of the Tagliamento River discharge in Italy under changing climate conditions

“…Moreover, increasing air temperatures and early snowmelt may increase the water temperatures in streams, lakes and wetlands and may have a dramatic effect on the ecological balance of these ecosystems. Water temperatures in surface ecosystems are highly sensitive to surface air temperature changes and may exceed the upper thermal limits of some species in the summer without adequate cool water supplies from groundwater discharge (groundwater is generally cooler than surface water in warmer months) and river water supplies (Gunawardhana et al, 2011). Therefore, the combined effects of surface air temperature changes (a 0.4-5.0 • C change during summer in the 2080-2099 time period compared to the baseline time period), early snowmelt, regular low-flow conditions and increased variations in river water discharge may be problematic for the protection of aquatic ecosystems under a changing climate.…”

Forecasting Groundwater Temperature with Linear Regression Models Using Historical Data

“…To estimate the impact of increasing air temperature on groundwater temperature, Taylor and Stefan () modeled vertical heat transport into groundwater by employing an analytical solution to a one‐dimensional heat conduction equation. Gunawardhana and Kazama (), Gunawardhana et al (), and Kurylyk and MacQuarrie () used the same approach but added advective vertical heat transport. By implementing the analytical solution of the resulting one‐dimensional advection‐diffusion equation, the authors modeled the impact of climate change on groundwater temperature in the Sendai plain, Japan.…”