NEWS NOTES ON SUSTAINABLE WATER RESOURCES Groundwater Temperature Susanne A Benz, Peter Bayer and Philipp Blum, Global patterns of shallow groun...

NEWS NOTES ON SUSTAINABLE WATER RESOURCES Groundwater Temperature Susanne A Benz, Peter Bayer and Philipp Blum, Global patterns of shallow groundwater temperatures , Environ. Res. Lett. 12 (2017) 034005. http://iopscience.iop.org/article/10.1088/1748-9326/aa5fb0/pdf Only meters below our feet, shallow aquifers serve as sustainable energy source and provide freshwater storage and ecological habitats. All of these aspects are crucially impacted by the thermal regime of the subsurface. Due to the limited accessibility of aquifers however, temperature measurements are scarce. Most commonly, shallow groundwater temperatures are approximated by adding an offset to annual mean surface air temperatures. Yet, the value of this offset is not well defined, often arbitrarily set, and rarely validated. Here, we propose the usage of satellite-derived land surface temperatures instead of surface air temperatures. 2 548 measurement points in 29 countries are compiled, revealing characteristic trends in the offset between shallow groundwater temperatures and land surface temperatures. Here it is shown that evapotranspiration and snow cover impact on this offset globally, through latent heat flow and insulation. Considering these two processes only, global shallow groundwater temperatures are estimated in a resolution of approximately 1 km _ 1 km. When comparing these estimated groundwater temperatures with measured ones a coefficient of determination of 0.95 and a root mean square error of 1.4 K is found.   This study will also be linked on the 2017 Reports and Publications Page of the Sustainable Water Resources Site at https://sites.google.com/site/sustainablewaterresources/">https://sites.google.com/site/sustainablewaterresources/   Tim Smith Sustainable Water Resources Coordinator Government Web Site, https://acwi.gov/ Sustainable Water Resources Site, https://sites.google.com/site/sustainablewaterresources/">https://sites.google.com/site/sustainablewaterresources/