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Study offers insights into climate change impact on ground water

Nov. 11, 2014, Germany – A study of two German cities suggests ground water in those areas is mirroring the warming pattern seen in the atmosphere.

Nov. 11, 2014, Germany – A study of two German cities suggests ground water in those areas is mirroring the warming pattern seen in the atmosphere.

The joint study, entitled "Observed groundwater temperature response to recent climate change," involved researchers at the Institute for Applied Geosciences (AGW), Karlsruhe, Germany, the Department of Earth Sciences, Zurich, Switzerland, and the University of New Brunswick, Department of Civil Engineering and Canadian Rivers Institute, Fredericton. It is published in the journal Hydrology and Earth System Sciences.

Researchers studied uninterrupted temperature
measurements of ground water flows around the cities of Cologne and
Karlsruhe, where the operators of the local waterworks have been
measuring the temperature of the ground water for 40 years.

"Climate change is known to have a considerable influence on many components
of the hydrological cycle. Yet, the implications for groundwater
temperature, as an important driver for groundwater quality, thermal use and
storage, are not yet comprehensively understood," says an abstract of the study. "Furthermore, few studies
have examined the implications of climate-change-induced groundwater
temperature rise for groundwater-dependent ecosystems."

The study examines the
coupling of atmospheric and ground water warming by employing stochastic and
deterministic models. Several decades of temperature time series
are statistically analyzed with regard to climate regime shifts in the
long-term mean. The observed increases in shallow ground water temperatures
can be associated with preceding positive shifts in regional surface air
temperatures, which are in turn linked to global air temperature changes, says the abstract.

The temperature data are also analyzed with an analytical solution to the
conduction–advection heat transfer equation to investigate how subsurface
heat transfer processes control the propagation of the surface temperature
signals into the subsurface. In three of the four monitoring wells, the
predicted ground water temperature increases driven by the regime shifts at
the surface boundary condition generally concur with the observed
ground water temperature trends. Due to complex interactions at the ground
surface and the heat capacity of the unsaturated zone, the thermal signals
from distinct changes in air temperature are damped and delayed in the
subsurface, causing a more gradual increase in ground water temperatures.

These signals can have a significant impact on large-scale ground water
temperatures in shallow and economically important aquifers, the researchers indicate: "These findings
demonstrate that shallow groundwater temperatures have responded rapidly to
recent climate change and thus provide insight into the vulnerability of
aquifers and groundwater-dependent ecosystems to future climate change."

Citation:
Menberg, K., Blum, P., Kurylyk, B. L., and Bayer, P.: Observed
groundwater temperature response to recent climate change, Hydrol. Earth
Syst. Sci., 18, 4453-4466, doi:10.5194/hess-18-4453-2014, 2014.

Read the final revised paper.