Temperature buffering by groundwater in ecologically valuable lowland streams under current and future climate conditions
article
Groundwater seepage influences the temperature of streams and rivers by providing a relatively cool
input in summer and warm input in winter. Because of this, groundwater seepage can be a determining
factor in the provision of suitable water temperatures for aquatic biota. Climate warming affects stream
and groundwater temperatures, and changes the thermal characteristics of streams leading to the potential
disappearance of habitats. In this study the importance of groundwater for the temperature of two
Dutch lowland streams and its possible role in mitigating the effects of climate change was determined
by combining field measurements and a modelling experiment. Stream temperature measurements using
fibre optic cables (FO-DTS) and sampling of 222Rn were done to map localized groundwater inflow.
Several springs and seepage ‘hot-spots’ were located which buffered the water temperature in summer
and winter. A stream temperature model was constructed and calibrated using the FO-DTSmeasurements
to quantify the energy fluxes acting on stream water. This way, the contribution to the
stream thermal budget of direct solar radiation, air temperature and seepage were separated. The model
was then used to simulate the effects of changes in shading, groundwater seepage and climate. Shading
was shown to be an important control on summer temperature maxima. Groundwater seepage seemed
to buffer the effect of climate warming, potentially making groundwater dominated streams more climate
robust. Protecting groundwater resources in a changing climate is important for the survival of
aquatic species in groundwater-fed systems, as groundwater seepage both sustains flow and buffers temperature
extremes.
input in summer and warm input in winter. Because of this, groundwater seepage can be a determining
factor in the provision of suitable water temperatures for aquatic biota. Climate warming affects stream
and groundwater temperatures, and changes the thermal characteristics of streams leading to the potential
disappearance of habitats. In this study the importance of groundwater for the temperature of two
Dutch lowland streams and its possible role in mitigating the effects of climate change was determined
by combining field measurements and a modelling experiment. Stream temperature measurements using
fibre optic cables (FO-DTS) and sampling of 222Rn were done to map localized groundwater inflow.
Several springs and seepage ‘hot-spots’ were located which buffered the water temperature in summer
and winter. A stream temperature model was constructed and calibrated using the FO-DTSmeasurements
to quantify the energy fluxes acting on stream water. This way, the contribution to the
stream thermal budget of direct solar radiation, air temperature and seepage were separated. The model
was then used to simulate the effects of changes in shading, groundwater seepage and climate. Shading
was shown to be an important control on summer temperature maxima. Groundwater seepage seemed
to buffer the effect of climate warming, potentially making groundwater dominated streams more climate
robust. Protecting groundwater resources in a changing climate is important for the survival of
aquatic species in groundwater-fed systems, as groundwater seepage both sustains flow and buffers temperature
extremes.
Topics
TNO Identifier
865852
Source
Journal of Hydrology X, 3, pp. 10031-10046.
Pages
10031-10046