EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The impact of global reservoir expansion on the present-day climate  

Inne Vanderkelen1, Nicole P. M. van Lipzig2, William J. Sacks3, David M. Lawrence3, Martyn Clark4, Naoki Mizukami3, Yadu Pokhrel5, and Wim Thiery1
Inne Vanderkelen et al.
  • 1Vrije Universiteit Brussel, Hydrology and Hydraulic Engineering, Brussels, Belgium (
  • 2KU Leuven, Department of Earth and Environmental Sciences, Leuven, Belgium
  • 3National Center for Atmospheric Research, Boulder, CO, USA
  • 4University of Saskatchewan, Centre for Hydrology and Coldwater Laboratory, Canmore, Canada
  • 5Michigan State University, Department of Civil and Environmental Engineering, East Lansing, MI, United States

By now, humans have constructed more than 45 000 large reservoirs across the globe, increasing the global lake area with 8%. These reservoirs have large impacts on freshwater processes and resources by impounding continental runoff and altering river flows. So far, the impact of reservoirs on the climate remains largely unknown, as they are typically not represented in current Earth System Models (ESMs). This is remarkable, as two-way interactions between reservoirs and climate are likely to alter hydrological extremes and impact future water availability.

Here we present the implementation of the role of reservoirs in the Community Terrestrial Systems Model (CTSM), a land surface model, by accounting for the increase in open water surfaces due to reservoir construction throughout the 20th century. To this end, we allow lake area to expand in the model, while ensuring that the surface energy and mass balances remain closed. We use reservoir and lake extent  from the state-of-the-art Global Reservoir and Dams (GRanD) and HydroLAKES data sets.

By conducting both land-only and coupled simulations with CTSM and the Community Earth System Model (CESM), we assess the added value of accounting for reservoir expansion in the land surface model performance and investigate their impacts on the mean climate and extremes. Globally, the effect of reservoirs on temperatures and the surface energy balance is small, but  responses can be substantial locally, in particular for grid cells where reservoirs make up a large fraction. Our results show that reservoirs reduce temperature extremes and moderate the seasonal temperature cycle, by up to -1.5 K (for reservoirs covering > 15% of the grid cell).

This study is an important step towards incorporating human water management in ESMs.


How to cite: Vanderkelen, I., van Lipzig, N. P. M., Sacks, W. J., Lawrence, D. M., Clark, M., Mizukami, N., Pokhrel, Y., and Thiery, W.: The impact of global reservoir expansion on the present-day climate  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-723,, 2021.

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