Modeling water cycle change in the U.S.: Climate versus human drivers

Abstract:

There is mounting evidence of profound hydrologic changes over the past century when instrumented records began, but to make correct attributions for the causes of the observed change, and to integrate and make sense of the changes in different branches of the water cycle and in different water stores, large-scale hydrologic models play an irreplaceable role. However, most of the existing large-scale water cycle models do not yet explicitly represent the anthropogenic forces which can no longer be neglected because the water cycle today is not natural anymore. In this study, an integrated modeling framework of continental-scale water cycle, with explicit representation of climate and human induced forces (e.g., irrigation, groundwater pumping) is developed and used to reconstruct the observed water cycle changes in the past and to attribute the observed changes to climatic and human factors. The new model builds upon two different previously developed models: a global land surface model called the Human Impacts and GroundWater in the MATSIRO (HiGW-MAT) [1,2] and a high-resolution regional groundwater model called the LEAF-Hydro-Flood [3]. The model is used to retro-simulate the hydrologic stores and fluxes in close dialogue with in-situ and GRACE satellite based observations at a wide range of river basin scales over the U.S., with a particular focus on the changes in groundwater dynamics in the High Plains and the Central Valley aquifers.

1. Pokhrel, Y., N. et al., (2012), J. Hydrometeor., 13, 255–269.

2. Pokhrel, Y. N., et al., (2015), Water Resour. Res., 51, 78–96.

3. Miguez-Macho, G., and Y. Fan (2012), J. Geophys. Res., 117, D15113.