Although often perceived as a natural hazard, drought can be affected by both climate anomalies and human activities such as water management. Using a high-resolution integrated modeling framework applied to the contiguous United States, a research team including scientists from the U.S. Department of Energy's Pacific Northwest National Laboratory found that local water extraction can intensify droughts, while reservoir regulation can alleviate them. The relative dominance of drought intensification or relief across regions is largely determined by water demand, which is projected to grow in the future and result in an increase in the spatial extent of extreme droughts at the national scale.
Since the 1960s, global human water consumption has increased by almost two and a half times due to the expansion of agriculture and urban areas, rapid population growth, and a higher standard of living. Greater water consumption can reduce streamflow to trigger local hydrological droughts, but reservoir regulations are designed to buffer drought by providing more reliable water supply. This study showed that understanding how hydrological drought and water demand might change in the future is imperative for sustainable water use and drought management.
Hydrological drought is characterized by streamflow deficit. Climate and human activities such as water management can disrupt normal streamflow and significantly alter current and future drought characteristics. Researchers analyzed model simulations to explore the impacts of water management on hydrological drought over the contiguous United States in a warming climate. This study used a high-resolution integrated modeling framework that represents water management in terms of both local surface water extraction and reservoir regulation. Scientists used the Standardized Streamflow Index to quantify hydrological drought.
Simulations showed that local surface water extraction consistently intensified drought at the regional to national scale, while reservoir regulation eased drought by increasing summer flow downstream of reservoirs. Drought intensification was most noticeable in areas with heavy water demand such as the Great Plains and California, while water management activities generally tended to relieve droughts in regions with lower water demands. The research team also found that droughts were more intense in future scenarios that included heavy bioenergy production, due to increased demand for irrigation. These results illustrate the need to account for the complex interactions among energy, water, and land systems when considering future climate impacts.
The U.S. Department of Energy Office of Science, Biological and Environmental Research supported this research through the Integrated Assessment Research and Earth System Modeling programs. The National Key Research and Development Program of China and the National Natural Science Foundation of China also supported this research.
W. Wan, J. Zhao, H.-Y. Li, A. Mishra, L.R. Leung, M. Hejazi, W. Wang, H. Lu, Z. Deng, Y. Demissie, H. Wang, "Hydrological Drought in the Anthropocene: Impacts of Local Water Extraction and Reservoir Regulation in the U.S." Journal of Geophysical Research: Atmospheres122 (2017). [DOI: 10.1002/2017JD026899]