Understanding interactions among climate, water, and vegetation with the Budyko framework

The Budyko models provide a transparent framework for analyzing climate-catchment interactions and therefore have been widely used to quantify the role of vegetation influencing the partitioning of precipitation (P) into evapotranspiration (ET) and runoff (R) at watershed to regional scales under a changing environment. This study provides a thorough review of the use of Budyko models for answering modern hydrological questions including the relation between vegetation dynamic and catchment ET (or runoff) and climate change impacts on water balances. Our synthesis suggests that: When vegetation structure and rooting characteristics are included, the Budyko models can explain over 90% of global spatial variations in ET. Budyko models showed that although climate dominates the catchment water balance, forest cover change also accounts for 30.7% ± 22.5% change in annual runoff in watersheds globally. Vegetation in watersheds with a low water retention capacity tends to play a more important role than climate change. Vegetation effects on annual runoff are most pronounced in water-limited regions and large scale revegetation can contribute 60% of the total observed change in the annual runoff. Budyko models can be used to study the joint impacts of climate seasonality (rainfall frequency and the time lag between maximum precipitation and net radiation) and vegetation on interannual variations in water balances. We conclude that vegetation dynamics have been successfully incorporated into the Budyko framework in the past two decades. The Budyko framework can be extended to provide insights into the interactions between climate, hydrology, and ecology. Uses of the Budyko framework for studying the hydrological effects of vegetation dynamics under a changing climate require analytical derivations of the models that incorporate climate-vegetation coevolution procedures.