Simulating human impacts on global water resources using VIC-5

Abstract. Questions related to historical and future water resources and water scarcity have been addressed by several macro-scale hydrological models over the last few decades. However, further advancements are needed to improve the integration of anthropogenic impacts and environmental flow requirements into hydrological models. The newly developed VIC-WUR model aims to increase the applicability of the VIC-5 model for water resource assessments, specifically by including human impacts and environmental flow requirements. To this end, VIC-WUR extends VIC-5 with modules for irrigation, domestic, industrial, energy and livestock water-use, environmental flow requirements for surface and groundwater systems, and dam operation. Model inputs of sectoral water demand were estimated independently and correlated well to reported national water withdrawals. VIC-WUR results, based on the newly developed modules, corresponded with results from reported global water withdrawals and other hydrological models, although differences exist. The VICWUR irrigation withdrawals were high compared to the other models but closer to the reported values, decreasing the gap between simulated and reported withdrawals. Irrigation withdrawals were probably high due to the inclusion of groundwater withdrawals and paddy irrigation in the model. Domestic and industrial water withdrawals were slightly lower than the reported values. Domestic and industrial withdrawals were probably insufficient due to low water availability, as the potential water withdrawals are more in line with reported values. Livestock water withdrawals were within the range of reported values and other models. The model additions comprehensively incorporate anthropogenic and environmental water use, which provides new opportunities for global water resource assessments. A preliminary assessment of environmental flow requirements shows competition between water resources allocated for human consumption and the environment, from ground and surface water sources. The improvements made here are a first step towards integrated water-food-energy nexus modelling. </jats:p>