Hydrologic signatures from human activities in ESM

Abstract 

To advance understanding of the interactions between human activities and the water cycle, an integrated terrestrial water cycle component has been developed for Earth system models. This includes a land surface model fully coupled to a river routing model and a generic water management model to simulate natural and regulated flows. A global integrated assessment model and its regionalized version for the U.S. are used to simulate water demand consistent with the energy technology and socio-economics scenarios. Human influence on the hydrologic cycle includes: regulation and storage from reservoirs, consumptive use and withdrawal from multiple sectors (irrigation and non-irrigation) and overall redistribution of water resources in space and time. As groundwater provides an important source of water supply for irrigation and other uses, the integrated modeling framework has been extended with a simplified representation of groundwater as an additional supply source, and return flow generated from differences between withdrawals and consumptive uses from both groundwater and surface water systems. 

The modeling framework with one-way coupling between the integrated assessment model and the land surface-river routing-water management model is applied and evaluated over the continental US with observed atmospheric forcing. The groundwater supply and return flow modules are evaluated by analyzing the simulated regulated flow, reservoir storage and supply deficit for irrigation and non-irrigation sectors over major hydrologic regions of the conterminous U.S. We demonstrate how human activities redistribute water resources in space and time and result in a clear east-west contrast in hydrologic signature due to sector-dependent relationships between water withdrawals and actual consumptive use, combined with different hydroclimate conditions, storage infrastructures, sectoral water uses and dependence on groundwater. The redistribution of surface and groundwater by human activities has important implications to the water and energy balances in the Earth system and land-atmosphere interactions.