Global separation of plant transpiration from groundwater and streamflow

What is it about?

We apply an existing stable-isotope-based methodology to test the widespread occurrence of ecohydrological separation -- plants using water of a character different to mobile water found in soils, groundwater and streams -- on a new global dataset and show that groundwater and streams are supplied by water that is distinct from the water that is retained in the soil and used by plants.

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Why is it important?

Regional- to global-scale climate projections are driven by land surface models (LSMs) that assume that plants and trees draw water from a singular, well-mixed subsurface reservoir. Moreover, the allocation of water as a resource for domestic and ecosystem use, as well as simulating the transport of contaminants in the subsurface, are both predicated on the same “single reservoir” model assumption. However, recent work in Oregon (USA) and Mexico has shown evidence of ecohydrological separation, whereby different subsurface compartmentalized pools of water supply either plant transpiration fluxes or the combined fluxes of groundwater recharge and streamflow. Heretofore, the ubiquity of this phenomenon has never been established.