Fewer Basins Will Follow Their Budyko Curves Under Global Warming and Fossil‐Fueled Development. Issue 8 (22nd August 2022)

• Record Type: Journal Article
• Authors: Jaramillo, Fernando; Piemontese, Luigi; Berghuijs, Wouter R.; Wang‐Erlandsson, Lan; Greve, Peter; Wang, Zhenqian
• Is Part Of: Water resources research. Volume 58:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-22
• Subjects: Budyko -- global warming -- evaporative ratio -- aridity index -- CMIP6; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2021WR031825
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: The Budyko framework consists of a curvilinear relationship between the evaporative ratio (i.e., actual evaporation over precipitation) and the aridity index (i.e., potential evaporation over precipitation) and defines evaporation's water and energy limits. A basin's movement within the Budyko space illustrates its hydroclimatic change and helps identify the main drivers of change. On the one hand, long‐term aridity changes drive evaporative ratio changes, moving basins along their Budyko curves. On the other hand, historical human development can cause river basins to deviate from their curves. The question is if basins will deviate or follow their Budyko curves under the future effects of global warming and related human developments. To answer this, we quantify the movement in the Budyko space of 405 river basins from 1901–1950 to 2051–2100 based on the outputs of seven models from the Coupled Model Intercomparison Project ‐ Phase 6 (CMIP6). We account for the implications of using different potential evaporation models and study low‐ and high‐emissions scenarios. We find considerable differences of movement in Budyko space regarding direction and intensity when using the two estimates of potential evaporation. However, regardless of the potential evaporation estimate and the scenario used, most river basins will not follow their reference Budyko curves (>72%). Furthermore, the number of basins not following their curves increases under high greenhouse gas emissions and fossil‐fueled development SP585 and across dry and wet basin groups. We elaborate on the possible explanations for a large number of basins not following their Budyko curves. Plain Language Summary: The Budyko framework relates aridity in the Earth's surface with the partitioning of rain into evaporation and runoff. The framework finds that all basins on earth fall on a curvilinear relationship between these two variables. It is argued that river basins will move along this curve if aridity is the only variable driving these changes in these partitioning. However, historical human development may cause river basins to deviate from these curves. The question is if basins will deviate or follow their Budyko curves under future global warming. To answer this, we quantify the movement in the Budyko space in 405 river basins from 1901 to 2100 based on the outputs of seven models from the Coupled Model Intercomparison Project ‐ Phase 6 (CMIP6). We account for the implications of using different potential evaporation models and study low‐ and high‐emissions scenarios. We find that regardless of the potential evaporation estimate and the scenario used most river basins will not follow their curves. Furthermore, the number of basins that do not follow their curves increases under the high greenhouse gas emissions and fossil‐fueled development scenario; SP585. We elaborate on the possible explanations for this large number of basins not following their Budyko curves. Key Points: We quantify CMIP6‐simulated movements in Budyko space of 405 river basins from 1901 to 2100 Most river basins will not follow their original Budyko‐curve trajectories The number of basins that do not follow their Budyko trajectories increases with the effects of global warming