Vegetation dynamics and climate seasonality jointly control the interannual catchment water balance in the Loess Plateau under the Budyko framework

Abstract

Within the Budyko framework, the controlling parameter ( ‰ in the Fu equation) is widely considered to represent landscape conditions in terms of vegetation coverage ( M); however, some qualitative studies have concluded that climate seasonality ( S) should be incorporated in ‰. Here, we discuss the relationship between ‰, M, and S, and further develop an empirical equation so that the contributions from M to actual annual evapotranspiration (ET) can be determined more accurately. Taking 13 catchments in the Loess Plateau as examples, ‰ was found to be well correlated with M and S. The developed empirical formula for ‰ calculations at the annual scale performed well for estimating ET by the cross-validation approach. By combining the Budyko framework with the semi-empirical formula, the contributions of changes in ‰ to ET variations were further decomposed as those of M and S. Results showed that the contributions of S to ET changes ranged from 0.1 to 74.8ĝ€% (absolute values). Therefore, the impacts of climate seasonality on ET cannot be ignored, otherwise the contribution of M to ET changes will be estimated with a large error. The developed empirical formula between ‰, M, and S provides an effective method to separate the contributions of M and S to ET changes.